Exam 3 Questions

Sexual reproduction results in an increase in genetic diversity because:

-During prophase I, genes that are paternally and maternally derived recombine so that the gametes have chromosomes that are different from the parents' chromosomes -During fertilization, the gametes that fuse are random so that a large number of chromosomal combinations are possible in the new organism -During metaphase I, the bivalents line up in a random orientation so that gametes inherit a random set of maternally and paternally derived chromosomes

Studies of rapidly dividing embryonic animal cells revealed:

-Increased synthesis of certain proteins in sync with the cell cycle -A periodic activation of protein kinases in sync with the cell cycle -That inhibition of protein synthesis blocks mitosis -That increased levels of cyclin proteins is correlated with activation of cyclin‐dependent kinase (CDK) enzymes

How do new cyclin proteins appear in the cytoplasm?

They are made through protein synthesis

Why are telomeres a necessary component of linear chromosomes?

They maintain the length of a chromosome because DNA is shortened every time it is replicated

How do CDKs promote cell division?

They phosphorylate proteins that allow passage through cell cycle checkpoints

Why are single-stranded binding proteins necessary for DNA replication?

They prevent the two parental strands from coming together again

Which type of cell junction prevents the movement of substances through the space between cells?

Tight junctions

What protein forms the contractile ring during cytokinesis in animal cells?

Actin

Which of the processes is most important for passage through the G1 cell cycle checkpoint?

Activation of cyclin‐dependent kinases

Under experimental conditions, we can delete the gene for the motor protein involved in contraction of the contractile ring during animal cell cytokinesis. Which of the results might you predict?

Additional rounds of the cell cycle continue producing a multinucleate cell

Which of the cellular junctions are physically linked with the cytoskeleton?

Adherens junctions and desmosomes

The enzyme responsible for joining Okazaki fragments together during DNA replication is:

DNA ligase

The enzyme responsible for proofreading a growing DNA strand and for replacing mismatched nucleotides is:

DNA polymerase

Telomerase is fully active in _____ and _____ cells, but almost completely inactive in _____ cells.

Germ; stem; somatic

Which of the sequences accurately represents the flow of electrons through living organisms?

H2O → photosynthesis → carbohydrate → cellular respiration → H2O

The similarity of meiosis II and mitosis suggests that meiosis likely evolved from mitosis

-Mitosis occurs in all eukaryotes and was certainly present in the common ancestor of all living eukaryotes -Meiosis is present in most, but not all, eukaryotes -Because the steps of meiosis are the same in all eukaryotes, meiosis is thought to have evolved in the common ancestor of all eukaryotes and has been subsequently lost in some groups

When a nucleotide is added to a growing nucleic acid strand during DNA replication, the incoming monomer is _____and the energy required to drive the polymerization is derived from _____.

A nucleoside triphosphate; cleaving a pyrophosphate

A gene associated with promoting normal cell division is called:

A proto-oncogene

In a diploid individual, there are two genes called "A" and "B" on one chromosome. One homolog of that chromosome carries A and B alleles of those genes, and the homologous chromosome carries different forms (alleles) of these same genes, a and b. If there is a single crossover between these two genes involving one pair of non‐sister chromatids during metaphase I of meiosis, the resulting four gametes would be:

AB, Ab, aB, ab

Why are primers needed for DNA replication?

DNA polymerase can only add nucleotides to an existing chain

At the end of mitosis, the daughter cells are _____, whereas at the end of meiosis the daughter cells are _____.

Diploid; haploid

In meiosis, recombination occurs:

During only prophase I and involves exchange between chromatids of homologous chromosomes

Which are examples of a motor protein?

Dynein, kinesin, myosin

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

False

Nondisjunction can only occur in the sex chromosomes and not the autosomes

False

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:

Females randomly inactivating one of the X chromosome in all cells

These enzymes play important roles in DNA replication: DNA polymerase, primase, ligase, helicase. In what order do they work during replication?

Helicase, primase, DNA polymerase, ligase

Prophase of meiosis I has some important differences from prophase of mitosis. These differences include: ______ pair, and ______ occurs.

Homologous chromosomes; crossing over

Where is the photosynthetic electron transport chain located in plant cells?

In the thylakoid membranes of the chloroplast

At which stage of the cell cycle could you see sister chromatids with a microscope?

M phase

Sister chromatids are separated during:

Meiosis II and mitosis

Which of the statements about the strands of a newly replicated DNA molecule is correct?

One strand is new, and the other is from the original molecule.

As a piece of linear DNA is replicated, the leading strand will have _____ RNA primer(s) and the lagging strand will have _____ RNA primer(s).

One; many

Which one of the statements best represents the relationship between cellular respiration and photosynthesis?

Photosynthesis stores energy in organic molecules, whereas cellular respiration releases it.

The main function of DNA polymerase is to add new nucleotides to the 3′ end of a growing chain. What is the second role of this enzyme in DNA replication?

Proofreading

What type of gene is c-src (cellular-src)?

Proto-oncogenes

The ATP generated by the photosynthetic electron transport chain is used in the _____ phase(s) of the Calvin cycle.

Reduction and regeneration

Processes that regulate cell division in mammals include:

-Rapid degradation of cyclins after CDK activation -Different cyclins and CDKs acting at different stages of the cell cycle to promote cell division -Production of cyclin proteins that activate CDK enzymes -Activated cyclin‐CDK complexes triggering cell cycle events

The second meiotic division resembles mitosis because:

-Spindle microtubules attach from opposite directions to the centromere of each sister chromatid pair -Sister chromatids are separated during anaphase II to become the chromosomes of the daughter cells -Chromosomes decondense during telophase II -The daughter cells have the same number of chromosomes as the parent cell

Which cellular conditions promote progression of the cell cycle?

-The accumulation of cyclins -The activation of CDKs -The expression and synthesis of cyclin proteins Binding of cyclins to CDKs

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

-The sister chromatids would not separate -The chromosome would not line up properly at metaphase -One of the daughter cells would have an extra copy of that chromosome

Given that the rate of DNA synthesis of a plasmid in yeast is 50 nucleotides per second and the circular plasmid replicates in 20 minutes, what is the approximate maximum size of the plasmid?

120,000

The leading strand is the daughter strand that has its _____ end pointed toward the replication fork and is therefore synthesized _____.

3'; continuously

A new nucleotide can only be added to the _____ end of a growing DNA strand. DNA therefore always grows in the _____ direction.

3′; 5′ to 3′

A cell in prophase I of meiosis has _____ as much DNA as each of the daughter cells following cytokinesis of meiosis II.

4 times

It is estimated that there are a total of 245 cells (roughly 50 trillion) in the adult the human body. Starting from a fertilized egg, how many cell divisions would be required to produce 245, assuming that every cell divides in every cycle?

45

What is the initial carbon input in the Calvin cycle?

CO2

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

Circular DNA attached to the plasma membrane and binary fission

Non-sister chromatids are:

Copies of homologs but not fully identical chromosomes

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.

Cytokinesis does not occur

Cancers develop stepwise over time because:

It takes multiple mutations of multiple genes to allow cancer cells to develop

Okazaki fragments are found on ______ strand of DNA.

Lagging strand

The assembly of what cytoskeletal structures are initiated by the M cyclin-CDK complex?

Microtubules

Microtubules and microfilaments are said to be "dynamic" elements of the cytoskeleton. In this case, "dynamic" means that:

Microtubules and microfilaments are assembled, disassembled, and then reassembled again in a regulated manner

The reducing agent during the Calvin cycle is:

NADPH

A student was studying cell growth using cells grown in laboratory cultures. The cultures were synchronized so that all of the cells passed through the same stage of the cell cycle at the same time. The cells were examined during five different periods of time, intervals (A-E). The amount of DNA present per cell was determined for each interval. The graph shows the result of this study. Most of the cells examined during interval A have half as much DNA as those measured in interval C. Therefore, most of the cells at interval B must have been in:

S phase

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

Second division nondisjunction

Photosynthesis is the pathway used to synthesize carbohydrates from:

Sunlight, CO2, and H2O

Which of the choices would be most likely to lead to the development of cancer?

The activation of an oncogene and the inactivation of a tumor suppressor gene

What would happen to the variation between organisms in a population if their DNA polymerase did not have a proofreading function?

The amount of variation would increase

What feature of double-stranded DNA makes it necessary to have a leading strand and a lagging strand during replication?

The antiparallel orientation of the strands

What would happen if telomerase stopped working in a cell in which it normally functions at high levels?

The cell would eventually die as the DNA continued to shorten

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

The cells would be smaller than normal

What important difference is there between meiosis in males and females?

The division of cytoplasm differs between males and females

Suppose a research team does a detailed analysis of the DNA sequence of all three copies of chromosome 21 from an individual with trisomy 21 (Down syndrome). They discover that two of the three chromosomes are essentially identical in sequence, whereas the third chromosome has a significant number of sequence differences. Which of the answer choices is consistent with this observation?

The extra chromosome 21 resulted from second-division nondisjunction in one of the parents' gametes

Synapsis is best described as:

The pairing of homologous chromosomes in prophase I

A homologous chromosome pair is best described as 2 chromosomes that have:

The same genes in the same order but possibly with different alleles of some of the genes

In a study of tadpole coloration, you noticed that a certain percentage of tadpoles in a population displayed a decreased ability to shift from dark coloration at night to light coloration during the day. These individuals were studied and found to have the normal number of melanophores and these melanophores produced normal amounts of melanin pigment granules. You remember reading that pigment granule transport in melanophores involves the cytoskeleton. Which part of the cytoskeleton would you suggest investigating as a potential source of the faulty color adjustment in these tadpoles?

Microtubules

The cytoskeleton of animal cells includes:

Microtubules, microfilaments, and intermediate filaments

The process of cytokinesis involves components of the cytoskeleton. It is most similar to what other cytoskeletal function?

Muscle contraction

The contractile ring that leads to cytokinesis in animal cells has been shown to be made primarily of actin filaments (microfilaments). Which motor protein would you predict is involved in contraction of the ring?

Myosin

During meiosis crossing over takes place between:

Non-sister chromatids

The most common form of hemophilia is a defect in blood clotting factor VIII, which is caused by a mutant form of a gene on the X chromosome. Boys who inherit that mutation from their mother suffer from uncontrolled bleeding. Girls carrying one copy of this mutation have near normal blood clotting. Uncommonly, a girl is born with hemophilia even though both parents have normal phenotypes. Which of the statements might explain hemophilia in a girl born to parents with normal blood clotting phenotypes?

Nondisjunction during sperm formation resulted in her receiving no sex chromosome from her father and an X chromosome from her mother; she is XO

RNA is involved in which of the cellular processes?

Transcription, translation, and DNA replication

There are no discernible phenotypic effects for an individual with the genotype XYY

True

Trisomy 21 (Down syndrome) is one of only a few examples of an autosomal trisomy in which the fetus develops to term and is born alive.

True

Phosphorylated p53 is a protein that accumulates in the nuclei of cells that have damaged DNA where it functions to block the cell cycle and activate DNA repair. The p53 gene that encodes this protein is an example of a(n):

Tumor suppressor gene

The parallel lines shown represent the paired strands of a DNA double helix. If this molecule undergoes one round of replication, which ends are shorter in the daughter molecules than in the parental molecules?

W and Z the 3' end

When we say that DNA replication is semiconservative, we mean that:

When DNA is replicated each new double helix contains one parental strand and one newly synthesized daughter strand