BIMS 320 Chapter 2

Gaucher disease

deficiency in fat metabolism leads to accumulation of fat in white blood cells in spleen, liver and bone marrow

common in individuals of Easter European Jewish descent

treatment → enzyme replacement therapy, bone marrow transplant

four classes of macromolecules

carbohydrates → simple sugars and large polymers

lipids → fats and oils, phospholipids and steroids

protein → polymers of amino acids

nucleic acids → polymers of nucleotides

two cellular domains of cells

plasma membrane

cytoplasm

nucleus

contains the genetic information necessary to to control cell structure and function

nucleolus

produces r

endoplasmic reticulum

smooth ER is involved in producing phospholipids and has many different functions in different cells. Rough ER is the site of synthesis of proteins for intracellular and extracellular use

ribosomes

aids in the production of proteins on the RER and in ribosomes complexes

golgi complex

sorts, chemically modifies and packages proteins produced on the RER

secretory vesicles

stores protein, hormones or enzymes in the cytoplasm awaiting a signal for release

lysosome

combines with food vacuoles and digest materials engulfed by cells

mitochondria

completes the breakdown of glucose, producing ATP

e phases of the cell cycle

interphase - time between cell divisions, G1, S, and G2 phases

mitosis - division of the nucleus nd segregation of the chromosomes into the future daughter cells

cytokinesis - division of the cytoplasm

chromatid

one strand of a duplicated chromosome

sister chromatids

two chromatids joined by a common centromere

each carries identical genetic information

kinases

enzymes that add phosphates to other proteins

cyclin-dependent kinases (CDKS) are inactive unless bound by their corresponding cyclin protein

CDKs are consistently present in cells

cyclins

proteins with no enzymatic activity of their own

only produced at certain times during cell cycle

bind to cyclin-dependent kinases (CDKs) to activate CDKs at appropriate times during cell cycle

cell cycle regulation

activated CKDs phosphorylate target proteins that regulate cell cycle progress

when cyclin production decreases, CDKs are unbound and go back to inactive state

cell cycle checkpoints

processes “checked” before next stage can begin

3 major checkpoints: G1, G2, M

interphase

G1 - stage begins immediately after mitosis, RNA, proteins, and organelles are synthesized

S - DNA is replicated and chromosomes form sister chromatids

G2 - mitochondria divide. precursors of spindle fibers are synthesized

mitosis

prophase - chromosomes condense, nuclear envelope disappears, centrioles divide and migrate to opposite poles of the dividing cell, spindle fibers form and attach to chromosomes

metaphase - chromosomes line up on the midline of the dividing cell

anaphase - chromosomes begin to seperate

telophase - chromosomes reach opposite poles, new nuclear envelope forms, chromosomes decondense

cytokinesis

cleavage furrows forms and deepens

cytoplasm divides

hayflick limit

cells can undergo only a certain number of cell division before they stop dviding; genetically controlled

human embryonic cells divide about 50 times while human adult cells divide 10-30 times; embyronic stem cells can divide indefinitely

allows growth to adulthood and cell replacement

meiosis

produces 4 haploid cells containing only one copy (paternal or maternal) of each chromosome

two rounds of meiotic division

• meiosis I - separates the homologous chromosomes, reduces the chromosome number from diploid to haploid, crossing over results in genetic variation

• meiosis II - separates the sister chromatids, equational division, four haploid cells result

Meiosis I

prophase I - chromosomes become visible, homologous chromosomes pair, and sister chromatids become apparent. recombination takes place

metaphase I - paired chromosomes align at equator of cell

anaphase I - paired homolgous chromosomes separate, members of each chromosome pair move to opposite poles

telophase I - chromosomes uncoil become dispersed

cytokinesis - cytoplasm divides, forming two cells

meiosis II

prophase II - chromosomes recoil, shorten

metaphase II - unpaired chromosomes become aligned at equator of cell

anaphase II - centromeres separate, daughter chromosomes which were sister chromatids, pull apart

telophase II - chromosomes uncoil, nuclear envelope re-forms. meiosis ends

cytokinesis - the cytoplasm divides, forming daughter cells

sperm

produced by males through spermatogenesis in the testes

Mitotic spermatogonia produce spermatocytes

Meiosis in spermatocytes produces haploid spermatids that mature into sperm cells

continually produced form puberty until death

four mature sperm from one primary spermatocyte

oocytes

produced by females through oogenesis in the ovary

Mitotic oogonia produce primary oocytes

Meiosis in primary oocytes produces ova

Finite number of primary oocytes arrested in meiosis I are produced during embryonic development

Meiosis II is completed upon fertilization

Only one mature ovum results from one primary oocyte

All of the following are functions of proteins, EXCEPT:

• structure

• protection

• hormones

• genetic instructions

• transport

genetic instructions

Which macromolecule is defined by its physical property of being insoluble in water?

• nucleic acids

• proteins

• carbohydrates

• lipids

lipids (fat)

In the life sciences, it's often helpful to interpret terminology using word roots. As an example, the "ribo-" in ribosome refers to the 5-carbon sugar ribose; the "-some" is from the Greek word root soma, for body. So you could think of ribosome as meaning "ribose-body." Which of these options makes the most sense of this interpretation for the term ribosome?

• Ribosomes are large, multi-unit molecular machines.

• Ribosomes are not classified as organelles because they are not surrounded by a membrane.

• Ribosomes are particle-like structures that contain RNA (as well as proteins), and ribose is the sugar in RNA.

Ribosomes are particle-like structures that contain RNA (as well as proteins) and ribose is the sugar in RNA

Translated from Latin, organelle means “little tool” this is appropriate as organelles fit inside the cell and perform a specific function

true

Suppose that you could synthesize an mRNA with a random sequence of nucleotides but attach the information for a normal signal sequence to one end, and that you could mark the molecule so you can observe what happens to it after you introduce it to the interior of a cell. choose the most logical prediction

• it would not enter the ER, because the signal sequence only works for the insulin protein

• the signal sequence would bind to the RNA-protein particle and protein would enter the ER

• it would not enter the ER, becuase the mRNA sequence is random and not meaningful in terms of the cell’s fitness

the signal sequence would bind to the RNA-protein particle and the protein would enter the ER

Flow of events in the endomembrane system

• mRNA is exported from the nuclus through a nuclear pore

• protein synthesis (linking amino acids via peptide bonds) begins in a ribosomes

• a signal sequence on the new protein binds to an RNA-protein particle, which interacts with a receptor on the ER membrane

• the protein enters the inside of the ER, through a channel

• folding and other processing occurs inside the ER

• processed proteins and other products move the Golgie from ER through “connection tunnels”

• products move through each sac in the Golgi, being processed, sorted by destination, and loaded into a vesicle

• kinesin walks along microtubules to carry vesicles that bud off the Golgi to their destination

• vesicles arrive at their destination and empty their cargo

the _______ is a unique organelle because it is the only location of DNA outside of the nucleus in animal cells

mitochondrion

which phrases best compare the genetic information of two sister chromatids

• the same genes on each chromatid

• the same alleles on each chromatid

• different genes on each chromatid

• different alleles on each chromatid

the same genes on each chromatid

the same alleles on each chromatid

ndicate which of the following is true regarding homologous chromosomes, non-homologous chromosomes, and sister chromatids. (Select all that apply.)

• Identical alleles for the same gene can be found on two non-homologous chromosomes.

• Two different alleles for the same gene can be found on a pair of sister chromatids.

• Two different genes can be found in the same location on a pair of homologous chromosomes.

• Two different alleles for the same gene can be found on a pair of homologous chromosomes.

two different alleles for the same gene can be found on a pair of homoglous chromosomes

Humans contain two copies of each chromosome, for example, two chromosome 16s. What are these copies called

• homologues

• sister chromatids

• non-homologous chromosomes

homologues

which phrases best compare the genetic information of homologous chromosomes

• identical genes on each chromosome

• different alleles on each chromosome

• identical alleles on each chromosome

• different genes on each chromosome

identical genes on each chromosomes

different alleles on each chromsomes

sister chromatids are

• matched pairs of chromosomes containing genes for the same traits in identical locations along their length

• chromosomes that do not contain the same genes or belong to the same pair

• identical copies of a chromosome present after replication

identical copies of a chromosome present after replication

sister chromatids are

• a pair of chromosomes in which each chromosome has been inherited from a different parent

• identical

• the result of DNA replication

• nonidentical

identical

the result of DNA replication

assuming no recombination between them, sister chromatids have

• an identical set of alleles

• a similar but not identical set of alleles

• a very different set of alleles

an identical set of alleles

What is the difference between a pair of sister chromatids and a pair of homologous chromosomes?

• Sister chromatids have the same alleles of the same genes, whereas homologous chromosomes may have different alleles of the same genes.

• Sister chromatids are present in both mitosis and meiosis, whereas homologous chromosomes are present only during meiosis.

  Sister chromatids have the same genes, whereas homologous chromosomes have different genes.

• Sister chromatids are present during all phases of the cell cycle, whereas homologous chromosomes are present only during division

sister chromatids have the same alleles of the same genes, whereas homologous chromosomes may have different allels of the same gene

When life scientists first began studying cell division in detail, they could only distinguish between two phases in the life of a cell: M phase, when mitosis could be observed under the microscopes available at the time, and interphase, when no visible changes were occurring to the chromosomes.

Under the current model of a 4-phase cell cycle with G₀ as an "exit," which phases are included in interphase? Select all that apply.

• G₀

• M

• G₂

• S

• G₁

G2, S, G1

In everyday English, a checkpoint is defined as "a staffed barrier, typically at a border, where travelers are subject to security checks."

Why is "checkpoint" a logical term for the "stop-or-go" intervals in the cell cycle? Select the single best answer.

• The function of cell cycle checkpoints is similar to border checkpoints for travelers, especially the analogy to DNA being "secure." In this analogy, checkpoints are "staffed" by regulatory proteins.

• Checkpoints are the points at which the cell cycle stops, meaning that the cell no longer divides but instead enters the mature G₀ phase of its existence.

• In essence, the cell has to "write a check" to be able to pass through that point and continue with the cell cycle.

The function of cell cycle checkpoints is similar to border checkpoints for travelers, especially the analogy to DNA being "secure." In this analogy, checkpoints are "staffed" by regulatory proteins.

If the regulatory proteins that act at cell cycle checkpoints fail, the consequences are minor. The cell will just push through and divide even if it has damaged DNA, which is the whole point of the cell cycle.

false

in which phase of the cell cycle is the decision made whether to enter G0 or continue through the cell cycle

G1

In which phases of the cell cycle do cells contain replicated chromosomes? Select all that apply.

• S

• G₁

• M

• G₀

• G₂

S, M, G2

Suppose a cell was unable to replicate its DNA during S phase. Which cell cycle checkpoint is the cell most likely unable to pass?

• None; the cell should be able to pass all of these checkpoints.

• the M checkpoint

• the G₂ checkpoint

• the G₁ checkpoint

G2 checkpoint

suppose a cell’s nutrient supply is too low. which cell cycle checkpoint is the cell most likely unable to pass

G1

Consider what happens in each part of the cell cycle. Why does DNA replication have to occur before mitosis, in interphase

• Mitosis is the same as saying cell division, and the physical separation that divides cells depends on DNA replication

• Mitosis is the same as saying chromosome replication - they are the same thing

• Mitosis sends one copy of each chromosome to each daughter cell so it cant occur unless replication has already made the copies

mitosis sends one copy of each chromosome to each daughter cell, so it cant occur unless replication has already made the copies

Which statements accurately describe characteristics of germ cells and/or somatic cells? Select all that apply.

• Cells that divide to form eggs are germ cells.

• Germ cells undergo meiosis.

• Cells that divide to form sperm are germ cells.

• A fertilized egg is a germ cell.

• Somatic cells undergo mitosis.

cells that divide to form eggs are germ cells

germ cells undergo meiosis

cells that divide to form sperm are germ cells

somatic cells undergo mitosis

the end result of mitosis

two cells with the same genetic content as the parent cell

dna replication and cell division

• dna replication begins

• sister chromatids are created

• sister chromatids are condensed

• replicated chromosomes line up along the middle of the cell

• sister chromatids separate

• newly individual chromosomes move to opposite sides and new nuclei begin to form

why is it important that DNA has replicated before the beginning of mitosis, which is when chromosome compaction occurs

• the cell is only large enough to hold sister chromatids during interphase

• gene transcription needs to occur during mitosis which is easier when chromosomes are compact

• DNA replication machinery would not be able to access the DAN if it was already compacted

• replicated copies need to move during early mitosis which is easier if they are compacted

DNA replication machinery would not be able to access the DNA if it was already compacted

replicated copies need to move during early mitosis which is easier if they are compact

a cell with 6 chromosomes starts mitosis. how many chromatids would be present in this cell during metaphase

12

what happens at the start of meiosis i is exactly what happens at the start of mitosis

false

what happens in the middle phase of meiosis I is identical to what happens in the middle phase (metaphase) of mitosis

false

the events that happen in meiosis I explain why meiosis is a reduction division. at the start of meiosis I, the cell is diploid: it has two of each chromosome type and homologous pairs present. at the end, each daughter cell is haploid

true

what happesn in the middle of meiiosis II is just what happens in the middle phase of mitosis, except that the cell is haploid instead of diploid

true

what happesn at the ed of meiosis II is just what happesn at the end of mitosis (anaphase and telophase) except that the cell is haploid instead of diploid

true

Meiosis II happens in the same way and at the same time in both daughter cells of Meiosis I. After both rounds of meiosis, how many daughter cells in total are produced by the single parent cell, which was diploid and had replicated chromosomes?

4

which three statements best describe the events that occur after homolgos synapse, early in meiosis I?

• After crossing over and recombination, sister chromatids are no longer identical--they each carry a unique combination of alleles.

• Crossing over is an appropriate term because the maternal and paternal physically cross each other (they look like an X under the microscope!).

• Recombination is an appropriate term because the chromosomes that result have a new combination of alleles--a mix of maternal and paternal.

• Crossing over and recombination are key aspect of mitosis.

after crossing over and recombination, sister chromatids are no longer identical- they each carry a unique combination of alleles

crossing over is an appropriate term because the maternal and paternal physically cross each other (they look like an X)

recombination is an appropriate term because the chromosomes that result have a new combination of alleles - a mix of maternal and paternal

In humans, n = 23. How many different unique combinations of maternal and paternal chromosomes are possible, each time meiosis occurs?

• 2 x 23 = 46

• 23^2 = 529

• 2^23 = 8,388,608

2²3 - 8,399,608

Which statements accurately describe genetic variation generated in meiosis? Select all that apply.

• At the end of Meiosis I, the two daughter cells are different genetically.

• The two daughter cells from each instance of Meiosis II are genetically identical even when crossing over occurs, because all that happens is that sister chromatids pull apart.

• If cells have different combinations of maternal and paternal chromosomes, they have different genotypes (remember that a genotype is a listing of the alleles present in a cell).

at the end of meiosis I, the two daughter cells are different genetically

if cells have different combinations of maternal and paternal chromosomes, they have different genotypes

Consider the similarities and differences between meiosis and mitosis. Which statements accurately describe both processes? Select the three best answers.

• The essence of mitosis is: Copy DNA, send one copy to each daughter cell.

• Both mitosis and meiosis require two rounds of division to be complete, meaning that in each process a single starting cell produces a total of four daughter cells.

• Meiosis II is essentially the same process as mitosis, except for two things: cells are haploid in Meiosis II, and in Meiosis II sister chromatids are no longer genetically identical.

• In mitosis, sister chromatids crossover and recombine. In meiosis, non-sister chromatids crossover and recombine.

• The most important difference between meiosis and mitosis is that homologs synapse in meiosis but stay independent of each other in mitosis

• DNA replication occurs before mitosis, before Meiosis I, and then again before Meiosis II.

the essence of mitosis is: copy DNA, send oen copy to each daughter cell

meiosis II is essentially the same process as mitosis except for two things; cells are haploid in Meiosis II, and in Meiosis II sister chromatids are no longer genetically identical

in mitosis, sister chromatids crossover and recombine, in meiosis, non-sister chromatids crossover and recombine

the most important difference between meiosis and mitosis is that homologs synapse in meiosis but stay independent of each other in mitosis

crossing over nad recombination

an exchange of genetic information taking place between two non-sister chromatids

biparental inheritance

when offspring receive one maternal copy and one paternal copy of each gene

synapsis

the process of homologous chromosomes pairing up and aligning in prophase I

chiasma

the points along the synapsed homologous chromosomes at which their chromatids connect: the sit of crossing over and recombination

bivalent/tetrad

present during meiosis I; consists of two homologous chromosomes and four total chromatids

mature sperm and eggs

• are the products of mitosis

• undergo meiosis

• undergo mitosis

• are the products of meiosis

are the products of meiosis

The X and Y chromosomes align during metaphase I of meiosis

• due to a pseudoautosomal region that is similar between the X and Y chromosomes.

• because the X and Y chromosomes are linked to one another.

• because the X and Y chromosomes contain nearly all of the same genes.

• because the chromosomes are similar in size.

due to a pseudoautosomal region that is similar between the X and Y chromosomes

Which of the following events does NOT occur during a normal meiosis?

• Homologous chromosomes separate during meiosis I.

• Two haploid gametes fuse to form a diploid cell.

• Sister chromatids separate during meiosis II.

• One diploid cell produces four haploid cells.

two haploid gamete fuse to form a diploid cell

DNA replication occurs

• before mitosis and meiosis

• during mitosis and meiosis

• during mitosis and before meiosis

• before mitosis and both before and during meiosis

before mitosis and meiosis

which term is a broad category of cells that make up the body and undergo mitosis

• somatic cell

• egg cell

• germ cell

• sperm cell

somatic cell

steps of spermatogenesis in order

spermatogonium

primary spermatocyte

secondary spermatocyte

spermatid

sperm

how many homologous pairs of chromosomes are in each human sperm after completion of meiosis

0

which sex chromosome can be found in a human male gamete (sperm cell) that has undergone normal meiosis

either X or Y

A spermatocyte goes through meiosis I and meiosis II to produce four sperm. Thinking just about the sex chromosomes and how they segregate during meiosis, which of the following statements is true?

• 2 of the 4 sperm will contain an X chromosome and 2, a Y chromosome, because the X and Y chromosomes act as homologous chromosomes during meiosis I.

• Each sperm will contain an X chromosome and a Y chromosome because the X and Y chromosomes assort independently of each other.

• 2 of the 4 sperm will contain an X chromosome and 2, a Y chromosome, because the X and Y chromosomes act as sister chromatids during meiosis II.

2 of the 4 sperm will contain an X chromosome and 2, a Y chromosome, because the X and Y chromosomes act as homologous chromosomes during meiosis I.

which types of cells can undergo meiosis

• germ cells

• somatic cells

• both

germ cells

why is the separation of chromosomes in meiosis I considered a reduction in ploidy for the daugther cells

because there is only one chromosome of each type