# MCB 181R Exam 1 (copy)

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Read the scenario: You get in your car to drive to class. You turn the key, and the engine starts making a clicking sound, but does not start (1). You think to yourself, "The battery must be dead" (2). So, you borrow the battery from your neighbor's car (with permission, of course) and exchange it for the one in your car (3). You figure that if the battery in your car is dead and you replace it then the car will start (4). You get in the car again, turn the key, and the car starts right up, and you make it to class on time (5).

Which sentence in the story provides support that the idea about the battery being dead is correct?

a) 1 b) 2 c) 3 d) 4 e) 5

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1

Read the scenario: You get in your car to drive to class. You turn the key, and the engine starts making a clicking sound, but does not start (1). You think to yourself, "The battery must be dead" (2). So, you borrow the battery from your neighbor's car (with permission, of course) and exchange it for the one in your car (3). You figure that if the battery in your car is dead and you replace it then the car will start (4). You get in the car again, turn the key, and the car starts right up, and you make it to class on time (5).

Which sentence in the story provides support that the idea about the battery being dead is correct?

a) 1 b) 2 c) 3 d) 4 e) 5

e) 5

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2

Many salmon return to the place where they were born to spawn (reproduce). You hypothesize that they use visual cues to find their way back. To test your hypothesis, you blind salmon and then examine whether or not they are able to return to their birthplace. You find that they are able to find their way back. The results of this experiment cause you to:

a) have rejected your hypothesis. b) can't determine whether your hypothesis is supported or not. c) have proven your hypothesis. d) supported your hypothesis. e) developed a theory about the role of vision in salmon navigation

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3

The language of DNA is converted to the language of RNA during the process known as:

a) translation. b) transcription. c) replication. d) central dogma.

b) transcription.

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Transcription is the process by which: a) proteins are synthesized from RNA molecules. b) DNA is synthesized from protein. c) RNA is synthesized from protein. d) RNA is synthesized from DNA. e) proteins are synthesized from DNA molecules.

d) RNA is synthesized from DNA.

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5

Dynamic instability is the rapid assembly and disassembly of:

a) microfilaments. b) both microfilaments and microtubules. c) microtubules. d) intermediate filaments.

c) microtubules.

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6

Not all eukaryotes contain a dynamic cytoskeleton or even any cytoskeleton. The smallest eukaryotes actually possess rigid cell walls composed of peptidoglycan, much like bacteria.

true false

false

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7

If you place sterile broth that contains no cells in a bowl out on a table overnight, by morning it will contain a growing population of bacterial cells. According to cell theory, how could this be explained?

a) The growing population of bacterial cells must have come from DNA in the broth that contained bacterial genes. b) The growing population of bacterial cells must have come from other bacteria cells that fell into the broth from the air. c) The growing population of bacterial cells must have come from liposomes formed from phospholipids in the broth. d) All of these choices are correct.

b) The growing population of bacterial cells must have come from other bacteria cells that fell into the broth from the air.

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8

Identify all the cell type(s) that belong(s) to each of the listed cellular components in the answer bank. An example of a prokaryotic cell type is bacteria. Examples of eukaryotic cell types include both animal and plant cells.

Eukaryotic Cell:

• nucleus

• cell wall

• organelles

Prokaryotic Cell:

• nucleoid

• cell wall

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9

All cells have:

a) a cell wall. b) internal compartments. c) a nucleus. d) genetic information.

d) genetic information.

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10

Mitochondria and chloroplasts both have inner and outer membranes.

true false

true

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11

A boy observes a robin outside of his window. He notices the robin repeatedly cocks its head to one side before pecking the ground. The boy suspects that when the robin cocks its head, it is actually listening for worms underground. His explanation of the bird's behavior is an example of:

a) a theory b) an experiment c) both a hypothesis and a theory d) an observation e) a hypothesis

e) a hypothesis

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12

A boy observes a robin outside of his window. He notices the robin repeatedly cocks its head to one side before pecking the ground. The boy suspects that when the robin cocks its head, it is actually listening for worms underground. If the boy notes that a single robin routinely catches a worm after cocking its head, then he would prove his hypothesis to be correct.

true false

false

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13

There are many different types of bacteria able to grow in a human host, and they are all disease-causing organisms.

true false

false

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14

You have learned that mutations can occur in DNA sequences. Are all mutations deadly?

a) yes because all mutations in DNA disrupt the central dogma b) yes all mutations are deadly c) no all mutations are benign d) no some mutations can have no effect or can be beneficial

d) no some mutations can have no effect or can be beneficial

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15

All cells have a _____, whereas not all cells have a(n) _____.

a) cell membrane; nuclear membrane b) nucleus; nuclear membrane c) nucleus; cytoplasm d) cell membrane; RNA or DNA e) nucleus; cell membrane

a) cell membrane; nuclear membrane

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Rickettsia typhi is a species of infectious bacterium that is an obligatory intracellular parasite. Since this bacterium is dependent on another organism, it would not be considered a living organism.

true false

false

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17

The cell theory states that all living organisms are composed from cells and that new cells can only arise from existing cells. Which statement supports the cell theory?

a) Embryonic cells undergo mitotic division. b) Human erythrocytes do not have nuclei and, therefore, are not real cells. c) Bacteria do not have mitochondria and, therefore, are not real cells. d) Cells can spontaneously arise from water and nutrients.

a) Embryonic cells undergo mitotic division.

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18

You have discovered a new species of prokaryote in a deep-sea thermal vent. Without any further characterization, which statement could you make about this species with a high degree of certainty?

a) The organisms are from the domain Archaea. b) None of the statements can be made with a high degree of certainty. c) These organisms store their genetic information as DNA. d) Information in RNA is transcribed into DNA and then translated into protein. e) Information in DNA is translated into RNA and then transcribed into protein.

c) These organisms store their genetic information as DNA.

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A student wants to do an experiment to determine how watering affects plant growth. She plants three plants of the same species and size in identical pots using the same soil and grows them at the same temperature. She waters the first plant once a day, the second plant twice a day, and the third plant three times a day. In this experiment, what is the independent variable?

a) soil and temperature b) the amount of water the plant receives c) the height of the plant at the end of the experiment d) the size of the pot

b) the amount of water the plant receives

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20

A student wants to do an experiment to determine how watering affects plant growth. She plants three plants of the same species and size in identical pots using the same soil and grows them at the same temperature. She waters the first plant once a day, the second plant twice a day, and the third plant three times a day. In this experiment, what is the dependent variable?

a) amount of water the plant receives b) size of the pot c) soil and temperature d) height of the plant at the end of the experiment

d) height of the plant at the end of the experiment

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21

A student wants to do an experiment to determine how watering affects plant growth. She plants three plants of the same species and size in identical pots using the same soil and grows them at the same temperature. She waters the first plant once a day, the second plant twice a day, and the third plant three times a day. In this experiment, what is (are) the controlled variable(s)?

a) soil, temperature, and size of the pot b) soil and temperature c) amount of water the plant receives d) height of the plant at the end of the experiment e) size of the pot

a) soil, temperature, and size of the pot

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Researchers seldom find prokaryotic cells that are greater than 100 micrometers in diameter. Why would the size of prokaryotic cells be restricted?

a) Prokaryotic cells do not have a phospholipid bilayer for a membrane. b) Prokaryotic cells have multifunctional genes that can encode several proteins on a single mRNA. c) Prokaryotic cells can exchange genetic information through pili, which are connections to nearby cells. d) Prokaryotic cells must absorb all of their nutrients from their environment and therefore require a high surface area to volume ratio. e) All of these answer choices are correct.

d) Prokaryotic cells must absorb all of their nutrients from their environment and therefore require a high surface area to volume ratio.

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23

If you place sterile broth that contains no cells in a bowl out on a table overnight, by morning it will contain a growing population of bacterial cells. According to cell theory, how could this be explained?

a) The growing population of bacterial cells must have come from liposomes formed from phospholipids in the broth. b) The growing population of bacterial cells must have come from other bacteria cells that fell into the broth from the air. c) All of these choices are correct. d) The growing population of bacterial cells must have come from DNA in the broth that contained bacterial genes.

b) The growing population of bacterial cells must have come from other bacteria cells that fell into the broth from the air.

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Prokaryotes absorb their nutrients from the environment. However, many prokaryotes have cell walls. What can you conclude from this information?

a) Cell walls are permeable, allowing nutrients to pass through. b) Prokaryotes live in hypertonic environments. c) Prokaryotes produce all their own nutrients with enzymes in the cell wall. d) Prokaryotic cell walls do not need to allow nutrients to pass through them because prokaryotes produce their own nutrients.

a) Cell walls are permeable, allowing nutrients to pass through.

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25

Which statement about mitochondria is true?

a) Mitochondria generate ATP. b) Mitochondria are subdivided into compartments known as thylakoids. c) Mitochondria are rich in pigments. d) Mitochondria are rich in pigments and rely on peptide gradients to function correctly. e) Mitochondria rely on peptide gradients to function correctly.

a) Mitochondria generate ATP.

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Mitochondria and chloroplasts are integral parts of the endomembrane system and are specifically connected to the endoplasmic reticulum.

true false

false

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Similarities between the DNA of certain bacteria and the DNA of both mitochondria and chloroplasts are evidence that these organelles originated as bacteria that were captured by another cell and, over time, evolved to their current function.

true false

true

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Given that plant cells have chloroplasts, mitochondria are actually unnecessary in plant cells.

true false

false

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29

Slime molds are studied by biologists because of their ability to change from a diffused state, where individual parts are separated, to a unified slimy mass of protoplasm that forms fruiting bodies that produce spores. According to cell theory, what must be true of slime molds?

a) All of these choices are correct. b) The diffused state occurs when slime mold cells separate, and the protoplasm stage occurs when slime mold cells cluster together to form spores. c) The diffused state is composed of separated cells, but the protoplasm stage is composed of cytoplasm without cell membranes or nuclei. d) The diffused state is composed of cytoplasm without membrane or nuclei, and the protoplasm stage occurs when the cytoplasm streams together. Cells only form when spores are made.

b) The diffused state occurs when slime mold cells separate, and the protoplasm stage occurs when slime mold cells cluster together to form spores.

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30

Which statement is true regarding chloroplasts?

a) Chloroplasts utilize carbon dioxide as a reactant. b) Unlike mitochondria, chloroplasts only contain an outer (and not an inner) membrane. c) Chloroplasts release carbon dioxide as a waste product. d) Chloroplasts are sites of cellular respiration.

a) Chloroplasts utilize carbon dioxide as a reactant.

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How many different kinds of membranes make up a chloroplast?

a) 3 b) 2 c) 1 d) 5

a) 3

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Mitochondria use a simple sugar called pyruvate and ADP when they function. What do mitochondria produce from those substrates?

a) proteins and nucleic acids b) ATP and carbon dioxide c) ATP and oxygen d) lipids and carbohydrates

b) ATP and carbon dioxide

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A skin cell in G2 of interphase has _____ as much DNA as it had in G1.

a) four times b) exactly c) half d) one-fourth e) twice

e) twice

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What is the function of the centromere?

a) to attach the chromosome to the spindle b) to attach the sister chromatids to each other c) to attach the DNA to the plasma membrane d) to organize the microtubules to form a spindle

b) to attach the sister chromatids to each other

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In which phase of mitosis do chromosomes condense?

a) prophase b) telophase c) metaphase d) anaphase

a) prophase

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Taxol is an anticancer drug that prevents uncontrolled cell proliferation by blocking the lengthening and shortening of microtubules, which causes arrest of the cell cycle. If dividing cells are treated with Taxol, what will occur?

a) The cells will be unable to divide the cytoplasm in cytokinesis. b) The cells will be unable to increase the cyclin levels required to pass the G1 checkpoint. c) The cells will be unable to replicate their chromosomes. d) The cells will be unable to form a mitotic spindle.

d) The cells will be unable to form a mitotic spindle.

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In which phase of mitosis do spindle microtubules shorten?

a) metaphase b) prophase c) anaphase d) telophase

c) anaphase

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All of these events happen during M phase except:

a) separation of sister chromatids. b) condensation of the chromosomes. c) synthesis of DNA. d) formation of the spindle.

c) synthesis of DNA.

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39

Indicate which roles belong to the Golgi apparatus.

Roles of the Golgi apparatus: a) adds carbohydrates to proteins and lipids b) degrades damaged or unneeded molecules c) synthesizes proteins destined for secretion d) modifies proteins and lipids produced in the ER e) synthesizes RNA f) sorts proteins and lipids to their final destination g) synthesizes fatty acids and phospholipids

a) adds carbohydrates to proteins and lipids

d) modifies proteins and lipids produced in the ER

f) sorts proteins and lipids to their final destination

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40

Which of the options is circled in this electron micrograph?

a) two double‐stranded DNA molecules b) one double‐stranded DNA molecule c) one single strand of a DNA molecule

b) one double‐stranded DNA molecule

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41

Which answer option lists the correct order of compartments traveled by a protein that is destined to be released from the cell by exocytosis?

a) rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, cell membrane b) smooth endoplasmic reticulum, rough endoplasmic reticulum, Golgi apparatus, cell membrane c) Golgi apparatus, rough endoplasmic reticulum, cell membrane d) rough endoplasmic reticulum, Golgi apparatus, cell membrane e) rough endoplasmic reticulum, Golgi apparatus, lysosome, cell membrane

d) rough endoplasmic reticulum, Golgi apparatus, cell membrane

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Which of the eukaryotic cell structures plays a role in protein trafficking and sorting?

a) peroxisomes b) the Golgi apparatus c) mitochondria d) vacuoles e) lysosomes

b) the Golgi apparatus

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43

Nondisjunction can occur in both mitosis and meiosis.

true false

true

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44

Homologous chromosomes separate from each other in:

a) meiosis I. b) mitosis. c) meiosis II. d) They never separate from each other during any form of cell division.

a) meiosis I.

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What important difference is there between meiosis in males and females? Refer to the figure shown.

a) The division of cytoplasm differs between males and females. b) Genetic recombination only occurs in females. c) Females replicate their chromosomes twice, whereas males only replicate their chromosomes once in meiosis. d) There are no differences in meiosis between males and females.

a) The division of cytoplasm differs between males and females.

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46

Diploid somatic cells of elephants have 56 chromosomes. If nondisjunction of one of an elephant's chromosomes occurs in meiosis II, the resulting sperm are expected to have the chromosome complement:

a) 29, 29, 28, 28. b) 56, 56, 57, 55. c) 29, 29, 27, 27. d) 28, 28, 29, 27. e) 28, 28, 28, 28.

d) 28, 28, 29, 27.

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47

During the formation of female gametes, nondisjunction of X chromosomes may occur during meiosis I, resulting in two types of eggs with different compositions of sex chromosomes. If normal X- or Y‐bearing sperm fertilize these two types of egg, which of the options are possible sex chromosome complements in the resulting fertilized egg?

a) XX and XY or XYY and YO b) XXX and XO or XXY and YO

b) XXX and XO or XXY and YO

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48

How does meiosis generate genetic diversity?

a) both crossing over at prophase I and random alignment of homologs at metaphase I b) random alignment of homologs at metaphase I only c) synapsis d) crossing over in prophase I only

a) both crossing over at prophase I and random alignment of homologs at metaphase I

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49

What process can account for the phenomenon wherein a normal XY male produces a sperm carrying two Y chromosomes?

a) first‐division nondisjunction b) translocation c) disjunction d) copy‐number variation e) second‐division nondisjunction

e) second‐division nondisjunction

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50

In which phase of mitosis does the nuclear envelope reform?

a) prophase b) metaphase c) telophase d) anaphase

c) telophase

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In which phase of mitosis do spindle microtubules shorten?

a) metaphase b) prophase c) anaphase d) telophase

c) anaphase

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52

Which statement represents a misconception about sister chromatids?

a) Sister chromatids are formed in the S phase of the cell cycle when the chromosome undergoes replication. Sister chromatids are identical or nearly identical DNA sequences. b) Sister chromatids are also called homologous chromosomes. c) Sister chromatids are attached to each other at their centromeres. d) Sister chromatids are formed when the prokaryotic circular chromosome attaches at the plasma membrane.

d) Sister chromatids are formed when the prokaryotic circular chromosome attaches at the plasma membrane.

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The microtubules that form the mitotic spindle extend out from the centrosome. Where would you expect to find the plus (fast-assembling) end of a spindle microtubule?

a) away from the centrosome and away from the kinetochore b) toward the centrosome and toward the kinetochore c) toward the centrosome and away from the kinetochore d) away from the centrosome and toward the kinetochore

d) away from the centrosome and toward the kinetochore

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54

Why don't plant cells use a contractile ring to divide their daughter cells?

a) Plant cells don't have an actin cytoskeleton. b) Plant cells don't form daughter cells. c) Plant cells don't have plasma membranes. d) A contractile ring can't "pinch" a cell wall.

d) A contractile ring can't "pinch" a cell wall.

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55

What would happen if a pair of sister chromatids only connected to the mitotic spindle at one of their kinetochores?

a) All of these choices are correct. b) The sister chromatids would not separate. c) The chromosome would not line up properly at metaphase. d) One of the daughter cells would have an extra copy of that chromosome.

a) All of these choices are correct.

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56

Which statement is true regarding binary fission?

a) DNA replication of the circular bacterial chromosome during binary fission is a bidirectional process, starting at one point but progressing in opposite directions. b) In binary fission, cell division is typically asymmetrical, with one daughter cell appearing much smaller than the other. c) Tubulin, rather than FtsZ, is responsible for cell division during binary fission. d) Proteins only anchor the original circular genome to the plasma membrane; the copy produced by DNA replication is free-floating.

a) DNA replication of the circular bacterial chromosome during binary fission is a bidirectional process, starting at one point but progressing in opposite directions.

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57

What would happen to the daughter cells if the G2 phase of the parent cell is shortened?

a) The cells would be smaller than normal. b) The cells would be larger than normal. c) The cells would be missing chromosomes. d) The cells would not undergo cytokinesis.

a) The cells would be smaller than normal.

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58

Suppose you are observing some cells with a microscope, and you see a cell that appears to be dividing. You can see that as the cell starts to pinch in half, the DNA seems to be attached to the plasma membrane via a membrane protein. On further analysis, you find that this organism's DNA is circular - that is, it consists of a closed loop. What can you conclude about this organism and its mode of cell division?

a) It is a eukaryote that is dividing by mitosis. b) It is a prokaryote that is dividing by binary fission. c) It is a eukaryote that is dividing by binary fission. d) It is a prokaryote that is dividing by mitosis.

b) It is a prokaryote that is dividing by binary fission.

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What characteristics do you expect to observe with a microscope if you investigate the division of mitochondria and chloroplasts in eukaryotic cells?

a) non-circular DNA and division by mitosis b) circular DNA attached to the plasma membrane and binary fission c) circular DNA attached to the plasma membrane and division by mitosis d) mitochondria and chloroplasts replicating by a process unlike binary fission or mitosis

b) circular DNA attached to the plasma membrane and binary fission

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60

A researcher is studying phases of the cell cycle in a population of cells during which there is an increase in the DNA content. This stage is most likely:

a) mitosis. b) cytokinesis. c) S phase. d) G1 phase.

c) S phase.

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Why would a compound that interferes with bacterial cell wall synthesis be useful for treating a bacterial infection?

a) It would prevent replication of DNA, and it would limit the spread of the infection. b) It would prevent the cells from becoming larger. c) It would prevent replication of DNA. d) It would limit growth of the bacterial population through cell division.

d) It would limit growth of the bacterial population through cell division.

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62

Muscle cells in the mammalian heart are multinucleate, meaning that multiple nuclei are present in the cytoplasm of individual large cells. Predict what is different about the cell cycle in a muscle cell.

a) Cytokinesis does not occur. b) The G1 and G2 phases are extended. c) S phase happens twice. d) M phase is inhibited.

a) Cytokinesis does not occur.

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The prokaryotic protein FtsZ is evolutionarily related to eukaryotic tubulin. What does this mean?

a) All of these choices are correct. b) The amino acid sequence for FtsZ is similar to tubulin. c) The overall protein structure of FtsZ is similar to tubulin. d) The two proteins evolved from a common ancestral protein. e) The gene sequence for FtsZ is similar to tubulin.

a) All of these choices are correct.

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What cellular process(es) is/are responsible for the increase in protein content associated with the gap phases of the cell cycle?

a) translation alone b) glycolysis c) both transcription and translation d) transcription alone

c) both transcription and translation

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The process of cell division in a prokaryotic cell is called:

a) binary fission. b) cytokinesis. c) mitosis. d) binary fusion.

a) binary fission.

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A cell that is not actively dividing is in what phase of the cell cycle?

a) G0 b) G1 c) M d) G2 e) S

a) G0

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67

A couple has a baby that only has one X chromosome and no Y chromosome. This could have occurred because:

a) All of these choices are correct. b) there was nondisjunction of homologous chromosomes in meiosis I in the mother. Meiosis in the father was normal. c) there was nondisjunction of sister chromatids in meiosis II of the father. Meiosis in the mother was normal. d) there was nondisjunction of the paired X and Y chromosomes in meiosis I in the father. Meiosis in the mother was normal. e) there was nondisjunction of the sister chromatids in meiosis II in the mother. Meiosis in the father was normal.

a) All of these choices are correct.

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In a person with the genotype XXY, we can tell that nondisjunction must have taken place in the mother and not the father.

true false

false

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69

Synapsis is best described as:

a) the pairing of homologous chromosomes in prophase I. b) the alignment of nonsister chromatids at the metaphase plate. c) the exchange of genetic information between sister chromatids. d) the exchange of genetic information between nonsister chromatids.

a) the pairing of homologous chromosomes in prophase I.

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70

A genotype is:

a) one of several forms of a gene. b) the particular combination of alleles present in a given organism. c) the expression of a trait in an individual. d) the location of a gene in a chromosome. e) None of the other answer options is correct.

b) the particular combination of alleles present in a given organism.

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71

The alignment of chromosomes at metaphase of meiosis II is most similar to the alignment of chromosomes during metaphase of mitosis.

true false

true

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72

An example of second-division nondisjunction is when sister chromatids fail to separate during anaphase of meiotic cell division.

true false

true

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73

During meiosis I:

a) genetically identical daughter cells are formed. b) gametes are formed. c) sister chromatids are separated. d) diploid cells become haploid.

d) diploid cells become haploid.

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74

Suppose a research team does a detailed analysis of the DNA sequence of all three copies of chromosomes 21 from an individual with trisomy 21 (Down syndrome). They discover that each of the three chromosomes has a unique DNA sequence. Which of the answer choices is consistent with this observation?

a) The extra chromosome 21 resulted from first-division nondisjunction in one of the parents' gametes. b) Both the mother and the father had nondisjunction events at chromosome 21 during meiosis to form their gametes. c) The extra chromosome 21 resulted from second-division nondisjunction in one of the parents' gametes. d) The extra chromosome 21 resulted from either first- or second-division nondisjunction in one of the parents' gametes. e) The chromosome 21 homologous pair failed to separate during meiosis I in the mother.

a) The extra chromosome 21 resulted from first-division nondisjunction in one of the parents' gametes.

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75

Meiosis _____ is similar to mitosis in that _____ separate.

a) II; sister chromatids b) II; homologous chromosomes c) I; nonsister chromatids d) I; homologous chromosomes e) I; sister chromatids

a) II; sister chromatids

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76

How must spindle microtubules attach to chromosomes during prometaphase of meiosis I?

a) Microtubules attach to the chiasma. b) Microtubules attach using their minus (slow assembling) ends. c) Microtubules attach at the centrosomes. d) Spindle microtubules from one pole attach to one kinetochore, and spindle microtubules from the other pole attach to the other kinetochore in a pair of sister chromatids, just like in mitosis. e) Spindle microtubules from one pole must attach to both kinetochores in a pair of sister chromatids.

e) Spindle microtubules from one pole must attach to both kinetochores in a pair of sister chromatids.

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77

In mammals, females have two copies of the X chromosome, whereas males have only one copy. Dosage compensation (equalization of the numbers of each gene) is accomplished in mammals by:

a) females randomly inactivating one of the X chromosome in all cells. b) males inactivating the X chromosome inherited from the mother in all the cells. c) males expressing the X-encoded genes at two times the level of the expression in female.

a) females randomly inactivating one of the X chromosome in all cells.

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78

What important difference is there between meiosis in males and females? Refer to the figure shown. Click to view full size.

a) The division of cytoplasm differs between males and females. b) Genetic recombination only occurs in females. c) Females replicate their chromosomes twice, whereas males only replicate their chromosomes once in meiosis. d) There are no differences in meiosis between males and females.

a) The division of cytoplasm differs between males and females.

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a) They fuse to form a new organism during fertilization. b) They have the same number of chromosomes as a somatic cell of the same individual. c) They are found in animals but not plants. d) They are formed by mitotic cell division. e) They are genetically identical to other gametes formed during meiosis.

a) They fuse to form a new organism during fertilization.

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80

During what step in meiosis do homologous chromosomes separate?

a) metaphase II b) anaphase I c) anaphase II d) prophase II

b) anaphase I

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81

Sexual reproduction results in an increase in genetic diversity because:

a) All of these choices are correct. b) during metaphase I, the bivalents line up in a random orientation, so that the gametes inherit a random set of maternally and paternally derived chromosomes. c) during fertilization, the gametes that fuse are random, so that a large number of chromosomal combinations are possible in the new organism. d) during prophase I, genes that are paternally and maternally derived recombine, so that the gametes have chromosomes that are different from the parents' chromosomes.

a) All of these choices are correct.

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82

There are laboratory techniques that allow researchers to determine the amount of DNA in cell nuclei. If you measure the amounts of DNA at the end of mitosis and at the end of meiosis, how do they compare to the starting cell (starting from prophase during mitosis and from prophase I during meiosis)?

a) the daughter cells at the end of mitosis have one-half the amount of DNA, and the daughter cells at the end of meiosis have one-fourth the amount of DNA. b) The daughter cells at the end of mitosis have one-half the amount of DNA, and the daughter cells at the end of meiosis have one-half the amount of DNA. c) The daughter cells at the end of mitosis have one-fourth the amount of DNA, and the daughter cells at the end of meiosis have one-half the amount of DNA.

a) the daughter cells at the end of mitosis have one-half the amount of DNA, and the daughter cells at the end of meiosis have one-fourth the amount of DNA.

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83

If a human has the genotype XXXY, they would:

a) have 2 inactivated X chromosomes and be female. b) have 3 inactivated X chromosomes and be male. c) have 1 inactivated X chromosome and be male. d) have 3 inactivated X chromosomes and be female. e) have 2 inactivated X chromosomes and be male.

e) have 2 inactivated X chromosomes and be male.

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84

Meiosis _____ is sometimes called reductional division because _____.

a) II; the sister chromatids are separated b) II; the number of chromosomes is reduced by half c) II; the amount of DNA per chromatid is reduced by half d) I; the sister chromatids are separated e) I; the number of chromosomes is reduced by half

e) I; the number of chromosomes is reduced by half

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85

One of the important cell cycle checkpoints occurs during M phase. It inhibits progression to anaphase until all of the chromosome kinetochores are correctly attached to microtubules of the spindle apparatus. If anaphase of mitosis occurred when the kinetochore microtubule connected to only one of the two spindle poles but not the other, what could result?

a) Down syndrome b) trisomy c) Turner syndrome d) nondisjunction

d) nondisjunction

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86

Suppose you analyze a time-lapse video of a cell under a microscope, and you observe what appears to be crosslike structures within a bivalent. Which of the answer choices is an interpretation of this observation?

a) The cell has completed S phase and is ready to begin cell division. b) The cell is probably from a plant that has four sets of chromosomes, rather than only two sets. c) The chromatids are the result of crossing over prior to initiation of prophase I of meiosis. d) These structures represent crossing over between nonsister chromatids.

d) These structures represent crossing over between nonsister chromatids.

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87

True-breeding plants are typically heterozygous for most genes.

true false

false

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88

In genetic crosses, the symbol Aa refers to a:

a) genotype. b) phenotype. c) morphotype. d) holotype. e) archetype.

a) genotype.

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89

In a homozygous genotype:

a) the individual will be phenotypically recessive. b) both alleles for a given trait are the same. c) the individual will be phenotypically dominant. d) both alleles for a given trait are the same, and the individual will be phenotypically dominant. e) the two alleles for a given trait are different.

b) both alleles for a given trait are the same.

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90

Which statement is true regarding the yellow-seed pea plants of Mendel's work?

a) Yellow-seed plants produce copious amounts of chlorophyll. b) Yellow-seed plants have an enzyme that breaks down chlorophyll. c) The yellow seed color of these plants is a recessive trait (compared to green seed color). d) Yellow seeds in these plants only appear in the F1 generation and never in the F2 generation. e) All of these choices are correct.

b) Yellow-seed plants have an enzyme that breaks down chlorophyll.

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91

A phenotype is:

a) one of several forms of a gene. b) the particular combination of alleles present in a given organism. c) the expression of a trait in an individual. d) the location of a gene in a chromosome. e) None of the other answer options is correct.

c) the expression of a trait in an individual.

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92

While doing a pedigree analysis of a royal family from the ancient Mayan empire, you notice that a prince with a genetic disease married a person from outside the royal family without a history of the disease in her family. Of their six children, two have the disease and four were not affected. The prince's mother and father also had this disease. If this disease is controlled by a single gene, then the most likely explanation for its occurrence in the children would be that the disease is:

a) dominant and is seen in heterozygous or homozygous dominant individuals. b) recessive and is only seen in homozygous recessive individuals such as the two affected children. c) a spontaneous mutation. d) dominant and is only seen in homozygous dominant individuals.

a) dominant and is seen in heterozygous or homozygous dominant individuals.

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93

A high school student wants to repeat Mendel's classic experiments for her science fair. To stay true to Mendel's work, what must the student do?

a) She must allow true-breeding pea plants to self-fertilize. b) She must remove the male organs (anthers) from plants they have designated as females. c) She must hand-pollinate the pea plants and keep careful track of the traits demonstrated by male and female parents. d) All of these choices are correct.

d) All of these choices are correct.

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94

Imagine that you have crossed two types of peonies, one with purple flowers and long stems and the other with white flowers and short stems. When you cross these flowers, you get the following numbers of progeny: 83 with purple flowers and short stems; 29 with purple flowers and long stems; 26 with white flowers and short stems; and 9 with white flowers and long stems. Based on these data, what can you say about genes that define flower color and stem length?

a) These genes sort independently. b) These genes are linked. c) You can make no statements about genes that define flower color and stem length.

a) These genes sort independently.

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95

You have an F2 generation derived from two true-breeding parents with different characteristics for the same trait (determined by a single gene). What percentage of the F2 generation with a dominant phenotype would you expect to be homozygous?

a) 0% b) 25% c) 33% d) 67% e) 75%

c) 33%

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96

Consider a situation in which a ranch has a herd of cattle with brown hides and short horns. All of their cattle are also relatively short in stature. If all of these were true-breeding traits, what could you say about the progeny of these cattle?

a) It is impossible to determine which traits will occur among the progeny—they will likely demonstrate different hide colors, horn lengths, and heights. b) The progeny of these cattle will have short horns but a variety of hide colors and heights. c) The progeny of these cattle will have a mix of brown, black, white, and spotted hides. d) Since the cattle are true breeding, the progeny of this herd will all be sterile. e) The progeny of these cattle will be short in stature and have brown hides and short horns.

e) The progeny of these cattle will be short in stature and have brown hides and short horns.

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97

The rare trait known as _____ causes failure of the middle long bones of fingers to develop. It is a _____ trait and will occur in approximately _____ of the offspring from matings in which one parent is affected.

a) brachydactyly; dominant; half b) brachydactyly; recessive; 25% c) epistasis; recessive; half d) epistasis; dominant; 75% e) incomplete penetrance; recessive; 25%

a) brachydactyly; dominant; half

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98

Your grandmother has a rare disease for which a new genetic test has just been developed. If you are interested in a genetic test to determine whether you are affected, what would you need to know in order to best interpret your test?

a) the degree of variable expressivity if you lack a copy of the affected allele b) if you have one or two copies of a dominant allele c) your father's genotype d) the penetrance of disease in people of your genotype

d) the penetrance of disease in people of your genotype

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99

A true-breeding black rabbit is crossed with a true-breeding white rabbit to produce an F1 generation of 16 individuals. If the black color trait is dominant, which answer option represents the expected phenotype of an F1 generation cross?

a) 16 black rabbits, 0 white rabbits, 0 gray rabbits b) 5 black rabbits, 4 white rabbits, 7 gray rabbits c) 0 black rabbits, 16 white rabbits, 0 gray rabbits d) 9 black rabbits, 3 white rabbits, 3 gray rabbits, and 1 spotted rabbit e) 0 black rabbits, 0 white rabbits, 16 gray rabbits

a) 16 black rabbits, 0 white rabbits, 0 gray rabbits

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100

Suppose you have a plant whose flowers have the dominant color phenotype, but you would like to know if the plant is homozygous or heterozygous. What cross, and with what predicted results, could you perform that would determine whether this plant has a heterozygous genotype?

a) cross to known homozygous dominant; ½ dominant phenotype: ½ recessive phenotype b) self-fertilization; 100% dominant phenotype c) testcross; ¼ recessive phenotype: ¾ dominant phenotype d) testcross; ½ dominant phenotype: ½ recessive phenotype

d) testcross; ½ dominant phenotype: ½ recessive phenotype

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