BIO EXAM 2

What do we mean when we use the terms monohybrid cross and dihybrid cross?

  A dihybrid cross involves organisms for two characteristics and a monohybrid cross involves only one.

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?

One phenotype was completely dominant over another.

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

 Traits are inherited in discrete units, and are not the results of "blending."

Why did Mendel continue some of his experiments to the F2 or F3 generation?

 to observe whether or not a recessive trait would reappear

Which of the following differentiates between independent assortment and segregation?

 The law of independent assortment requires describing two or more genes relative to one another.

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?

that the parents were both heterozygous for a single trait

Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that

  traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.

Mendel was able to draw his ideas of segregation and independent assortment because of the influence of which of the following?

 His reading of the scientific literature current in the field.

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

  anaphase I of meiosis

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

50%

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

  8

A character trait that behaves in a completely dominant manner

can be seen in the heterozygous state

In Vampires, long fangs are dominant to short fangs. If a heterozygous long fanged Vampire mates with a short-fanged Vampire – what fraction of their offspring is expected to be long fanged?

  ½

A genetic cross between two heterozygous Pikachu with yellow ears will result in what percent of black eared Pikachu? Yellow ears are dominant to black ears.

25%

In Pac-Man ghosts, the orange phenotype (O) is completely dominant to the blue phenotype (o). If you have a ghost with an orange phenotype but are not sure of its genotype, which of the following ghosts would you cross it with to determine if this ghost with the orange phenotype is homozygous or heterozygous at the color gene?

 A true breeding ghost that is blue

In humans, brown hair is dominate over blonde hair. Unattached earlobes are 

dominate over attached. Cross a male that is heterozygous for both traits with a female that is heterozygous for both traits. What is the percentage of offspring that are homozygous dominant for hair and heterozygous for earlobes?

  13%

Why did Mendel specifically choose pea plants?

Pea plants have several traits and controlled pollination

When crossing two true-breeding parents, what generation are their offspring?

 F1

What does not cause a noticeable effect on heterozygous organisms?

recessive traits

Hybridization is the result of what?

  mating 2 true-breeding parents

The result of selfing your population; no genetic variation

  Inbreeding

What type of reproduction did Mendel's experiments use?

  sexual

What is the Law of Segregation?

  2 alleles segregate during gamete formation and end up in different gametes

Mendel's Model contains 4 hypotheses: Select all that apply.

 Alternate versions of genes account for variation

  The two alleles for a heritable character segregate during gamete formation and end up in different gametes

  If the two alleles at a locus differ, the dominant allele determines the organism’s appearance

  For each character, an organism inherits 2 alleles, one from each parent

What is the difference between a character and a trait?

 Character is a heritable feature that varies among individuals while a trait is a variant of the character

Mycoplasmas are bacteria that lack cell walls. On the basis of this structural feature, which statement concerning mycoplasmas should be true?

They are subject to lysis in hypotonic conditions.

Which statement about bacterial cell walls is false?

 Cell walls prevent cells from dying in hypertonic conditions.

Jams, jellies, preserves, honey, and other foodstuffs with high sugar content hardly ever become contaminated by bacteria, even when the food containers are left open at room temperature. This is because bacteria that encounter such an environment

undergo death by plasmolysis.

The typical prokaryotic flagellum features

 a complex "motor" embedded in the cell wall and plasma membrane.

Which statement about the genomes of prokaryotes is correct?

 Prokaryotic genomes are composed of circular DNA.

Prokaryotes' essential genetic information is located in the

 nucleoid.

Regarding prokaryotic genetics, which statement is correct?

Mutation is a primary source of variation in prokaryote populations.

Hershey and Chase performed an elegant experiment that convinced most biologists that DNA, rather than protein, was the genetic material. This experiment subjected bacteria to the same gene transfer mechanism as occurs in

transduction.

Which of the following obtain energy by oxidizing inorganic substances/energy that is used, in part, to fix CO2?

chemoautotrophs

Mitochondria are thought to be the descendants of certain alpha proteobacteria. They are, however, no longer able to lead independent lives because most genes originally present on their chromosome have moved to the nuclear genome. Which phenomenon accounts for the movement of these genes?

 horizontal gene transfer

Which statement about the domain Archaea is true?

Genetic prospecting has recently revealed the existence of many previously unknown archaean species.

If archaeans are more closely related to eukaryotes than to bacteria, then which of the following is a reasonable prediction?

Archaean ribosomes should be larger than typical prokaryotic ribosomes.

Assuming that each of these possesses a cell wall, which prokaryotes should be expected to be most strongly resistant to plasmolysis in hypertonic environments?

extreme halophiles

In general, what is the primary ecological role of prokaryotes?

breaking down organic matter

Which of the following traits do archaeans and bacteria share?

1. presence of plasma membrane

2. lack of a nuclear envelope

In a bacterium that possesses antibiotic resistance and the potential to persist through very adverse conditions, such as freezing, drying, or high temperatures, DNA should be located within, or be part of, which structures?

1. nucleoid region

2. endospore

3. plasmids

Which two structures play direct roles in permitting bacteria to adhere to each other, or to other surfaces?

1. capsules

2. fimbriae

If all prokaryotes on Earth suddenly vanished, which of the following would be the most likely and most direct result?

The recycling of nutrients would be greatly reduced, at least initially.

Foods can be preserved in many ways by slowing or preventing bacterial growth. Which of these methods should be least effective at inhibiting bacterial growth?

Closing previously opened containers: prevents more bacteria from entering, and excludes O2.

Broad-spectrum antibiotics inhibit the growth of most intestinal bacteria. Consequently, assuming that nothing is done to counter the reduction of intestinal bacteria, a hospital patient who is receiving broad-spectrum antibiotics is most likely to become

 deficient in certain vitamins and nutrients.

How do we describe transformation in bacteria?

  assimilation of external DNA into a cell

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

 DNA contains phosphorus, whereas protein does not.

Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?

the diameter of the helix

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?

sequence of bases

In an analysis of the nucleotide composition of DNA, which of the following will be found?

 A + C = G + T

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?

  Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

What is meant by the description "antiparallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

 the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose. 

The leading and the lagging strands differ in that

  the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?

 double-stranded DNA, four kinds of dNTPs, primers, origins

What is the function of topoisomerase?

  relieving strain in the DNA ahead of the replication fork 

Which of the following statements describes the eukaryotic chromosome?

 It consists of a single linear molecule of double-stranded DNA plus proteins.

Which of the following statements is true of histones?

  Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.

Why do histones bind tightly to DNA?

 Histones are positively charged, and DNA is negatively charged.

Which of the following statements describes chromatin?

  Heterochromatin is highly condensed, whereas euchromatin is less compact.

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

The elongation of the leading strand during DNA synthesis

 depends on the action of DNA polymerase. 

In a nucleosome, the DNA is wrapped around

histones.

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

  nuclease, DNA polymerase, DNA ligase

In his transformation experiments, what did Griffith observe?

 Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

The experiments of Meselson and Stahl showed that DNA __________.

 replicates in a semiconservative fashion

One strand of a DNA molecule has the base sequence 5′-ATAGGT-3′. The complementary base sequence on the other strand of DNA will be 3′- __________-5′.

 TATCCA

DNA polymerase adds nucleotides to the __________ of the leading strands, and to the __________ of the lagging strands (Okazaki fragments).

  3′ end ... 3′ end

A scientist assembles a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have __________. 

 the protein and DNA of T4

In an important experiment, a radioactively labeled bacteriophage was allowed to infect bacteria. In a first trial, the phage contained radioactive DNA, and radioactivity was detected inside the bacteria. Next, phage-containing radioactive protein was used, and the radioactivity was not detected inside the bacteria. These experiments led to the conclusion that __________. 

 the genetic material of the phage is DNA

Until Hershey and Chase showed that DNA was the genetic molecule of the phages they studied, what class of molecules was considered the best candidate for carrying genetic information and why?

 proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed

Monomers for the synthesis of DNA are called __________. 

  amino acids

In DNA, the two purines are __________, and the two pyrimidines are __________.

  adenine and guanine ... cytosine and thymine

The two antiparallel strands of nucleotides that form the DNA double helix are held together by __________. 

  hydrogen bonds between nucleotide bases

During the replication of DNA, __________.

both strands of a molecule act as templates

Photosynthesis is not responsible for

  fossil fuels.

Where does the Calvin cycle take place?

 stroma of the chloroplast 

When oxygen is released as a result of photosynthesis, it is a direct by-product of

splitting water molecules. 

Which of the events listed below occurs in the light reactions of photosynthesis?

Light is absorbed and funneled to reaction-center chlorophyll a.

Reduction of oxygen to form water occurs during

respiration only. 

Reduction of NADP+ occurs during

 photosynthesis. 

In metabolic processes of cell respiration and photosynthesis, prosthetic groups such as heme and iron-sulfur complexes are encountered in components of the electron transport chain. What do they do?

 both oxidize and reduce during electron transport 

The reactions that produce molecular oxygen (O2) take place in

 the light reactions alone.

What is the primary function of the Calvin cycle?

 synthesize simple sugars from carbon dioxide 

Reactions that require CO2 take place in

 the Calvin cycle alone.

Which of the following are directly associated with photosystem I?

 receiving electrons from the thylakoid membrane electron transport chain

What does the chemiosmotic process in chloroplasts involve?

 establishment of a proton gradient across the thylakoid membrane

In a plant cell, where are the ATP synthase complexes located?

thylakoid membrane and inner mitochondrial membrane

Generation of proton gradients across membranes occurs during

 both photosynthesis and respiration

The NADPH required for the Calvin cycle comes from

 reactions initiated in photosystem I.

Rubisco is __________. 

the enzyme in plants that captures CO2 to begin the Calvin cycle

What structure is formed by the reaction center, light-harvesting complexes, and primary electron acceptors that cluster, and is located in the thylakoid membrane?

 the photosystem

The use of non-C3 and non-CAM plants as crops may be limited in some regions because on hot, dry days, they close their stomata. What happens as a result of closing their stomata?

 Oxygen from the light reactions in the leaf builds up.

  Carbon dioxide is prevented from entering the leaf.

  In a process called photorespiration, rubisco binds oxygen instead of carbon dioxide

  Water loss is reduced.

The light reactions of photosynthesis supply the Calvin cycle with

ATP and NADPH. 

Which of the following sequences correctly represents the flow of electrons during photosynthesis?

  H2O → NADPH → Calvin cycle

How is photosynthesis similar in C4 plants and CAM plants?

In both cases, rubisco is not used to fix carbon initially.

In mechanism, photophosphorylation is most similar to

oxidative phosphorylation in cellular respiration.

What misconception did scientists overcome when studying plant biology?

 that plants eat soil as fuel

What three layers are considered ground tissue in plants?

collenchyma, sclerenchyma, and parenchyma

What are the byproducts of light reactions?

ATP and NADPH