Exam 3

Question 1

At what point of the cell cycle would you see a chromosome look like this? (sister chromatids, centromeres on each chromatid)

Answer 1

Metaphase (M)

Question 2

The chromosome begins M phase looking as shown. When does it split?

Answer 2

Anaphase (A)

Question 3

What best describes the kinetochore?

Answer 3

Structure composed of several proteins that associate with the centromere region of a chromosome and that can bind to spindle microtubules

Question 4

From prophase through metaphase of mitosis, each chromosome has ___ DNA molecules, while from anaphase through telophase of mitosis, each chromosome has ___ DNA molecule

Answer 4

Two; one

Question 5

If you were given a slide and told that the cells on it were performing cytokinesis, how would you tell if you had plant cells or animal cells?

Answer 5

Look for a cell plate or cleavage furrow

Question 6

Which comes immediately after S phase in the cell cycle?

Answer 6

G2

Question 7

If a cell that had two copies of each chromosome, but problems with the spindle caused the sister chromatids to remain attached to each other and to only one spindle pole, what cells would result?

Answer 7

Cells with 4 copies of each chromosome and 0 copies of each chromosome

Question 8

You are observing a line of rat cells and see that they repeatedly make mistakes in the cell cycle by going through the G2 checkpoint too early. This could be due to a ___.

Answer 8

Problem with the expression of a cyclin

Question 9

The decline of MPF activity at the end of mitosis is due to

Answer 9

The degradation of cyclin

Question 10

If a cell does not receive a go-ahead signal at G1 checkpoint during cell cycle, name the phase it enters as a nondividing state.

Answer 10

G0

Question 11

Binary fission is more like animal cell division because

Answer 11

Bacteria and animals both pinch in to separate cytoplasm into two pieces

Question 12

Privet shrubs and humans each have diploid number of 46 chromosomes per cell. Why are the two species so dissimilar?

Answer 12

The two species have appreciably different genes

Question 13

Why is it more practical to prepare karyotypes by viewing somatic diploid cells rather than haploid gametes?

Answer 13

Both sets of chromosomes, which are present in somatic diploid cells, need to be examined.

Question 14

Why does sexual reproduction (meiosis) have an advantage over asexual reproduction (mitosis)?

Answer 14

Meiosis increases genetic variation among offspring

Question 15

The mosquito Aedes aegypti has a karyotype of 2n=6. Through independent assortment alone, how many chromosomal combinations can be made during meiosis?

Answer 15

8

Question 16

A human cell containing 22 autosomes and a Y chromosome is

Answer 16

a sperm

Question 17

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I will be

Answer 17

2x

Question 18

Which of the following is not a reason that peas were well suited for Mendel’s breeding experiments?

Answer 18

Peas have an unusually long generation time

Question 19

A pea plant is heterozygous at the independent loci for flower color Pp and seed color Yy. What types of gametes can it produce?

Answer 19

Four gamete types: pY, py, PY, and Py

Question 20

A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates

Answer 20

dominance

Question 21

The following offspring were observed from many crossing of the same pea plants. (456 purple axial, 152 purple terminal, 140 white axial, 52 white terminal) The alleles for purple, white, axial, and terminal characters are P,p,A,a respectively. What genotypes are the parents?

Answer 21

PpAa x PpAa

Question 22

In dragons, wings are a dominant trait, but some dragons are born wingless. If a wingless dragon is crossed with one that is heterozygous, how many of its offspring will be wingless?

Answer 22

50%

Question 23

Suppose that Mendel’s hypothesis that inheritance is “particulate” rather than due to blending were wrong. Which observation would he NOT have made?

Answer 23

Crossing two-purple flowered heterozygotes produced purple-flowered and white-flowered plants.

Question 24

In peas, the allele for tall stems (T) is dominant to dwarf stems (t), and axial flowers (A) is dominant to terminal flowers (a). A plant of unknown genotype with tall stems and axial flowers is crossed with a plant with dwarf stems and terminal flowers. Among the offspring are 38 plants with tall stems and axial flowers, and 36 plants with tall stems and terminal flowers. What is the previously unknown genotype?

Answer 24

TTAa

Question 25

Morgan and his colleagues worked out a set of symbols to represent fly genotypes. Which of the following is representative?

Answer 25

Xw+ or Xw

Question 26

In some species of Drosphilia, there are genes on the Y chromosome that are not on the X chromosome. Imagine that a new allele arises on the Y chromosome and reduces size by half of individuals with the new allele. Which of the following statements is accurate with regard to this situation?

Answer 26

This allele is passed to all male but no female offspring of a male with the allele.

Question 27

In cats, an X-linked gene affects coat color. The O allele produces an enzyme that converts eumelanin, a black/brown pigment into phaeomelanin, an orange pigment. The o allele is recessive to O and produces a defective enzyme, one that does not convert eumelanin into phaeomelanin. Which of the following statements is accurate?

Answer 27

The phenotype of o-Y males is black/brown because the nonfunctional allele o does not convert eumelanin into phaeomelanin.

Question 28

Genes which tend to be inherited together are called

Answer 28

Linked genes

Question 29

Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA?

Answer 29

Franklin

Question 30

What enzyme compensates for replication-associated shortening of linear chromosomes?

Answer 30

Telomerase

Question 31

Which of the following results from Griffith's experiment is an example of transformation?

Answer 31

Mouse dies after being injected with a mixture of heat-killed S and R living cells

Question 32

Suppose a double-stranded DNA molecule was shown to have 22% guanine bases. What would be the expected percentage of adenine bases in the molecule?

Answer 32

28%

Question 33

Consider the replication bubble diagramed (5'-L-M-3' / 3'-N-O-5'). Which letters represent leading strands?

Answer 33

L and O

Question 34

Consider the replication bubble diagramed (5'-L-M-3' / 3'-N-O-5'). Which letters represents places where one could find Okazaki fragments?

Answer 34

M and N

Question 35

In Meselson and Stahl's experiment proving semiconservative DNA replication, they started with bacteria grown in a heavy isotope of nitrogen and then switched them to a light isotope. They then observed the DNA density after one and two rounds of replication. What was the result after one round of replication?

Answer 35

All hybrid DNA

Question 35

Imagine a bacterial replication fork. Synthesis of which new strand(s) would be affected by mutations in the enzyme DNA polymerase III?

Answer 35

Both leading and lagging strands

Question 36

In Meselson and Stahl's experiment proving semiconservative DNA replication, they started with bacteria growth in a heavy isotope of nitrogen and then switched them to a light isotope. They then observed the DNA density after one and two rounds of replication. What was the result after two rounds of replication?

Answer 36

Equal amounts of light and hybrid DNA

Question 37

Which of the following terms does not directly pertain to translation?

Answer 37

DNA

Question 38

The temple strand of a given gene includes the sequence 3'-GCCACGTATCA-5'. What is the sequence of the nontemplate strand?

Answer 38

5'-CGGTGCATAGT-3'

Question 39

Which of the following is the best example of gene expression?

Answer 39

Mouse fur color results from pigment formed by gene-encoded enzymes

Question 40

In the transcription process, in which process order (1,2,3) does the RNA polymerase bind to the promoter, in which is the RNA transcript released, and in which is the RNA transcript extended?

Answer 40

1,3,2

Question 41

Which of the following components does not form part of the transcription initiation complex at a eukaryotic promoter?

Answer 41

Transfer RNA

Question 42

Aminoacyl-tRNA synthetase is an enzyme whose function is to___.

Answer 42

Link tRNA to its corresponding amino acid

Question 43

Which of the following is a modification made to eukaryotic mRNA before it is exported to the cytosol?

Answer 43

All of the above (5' end is capped, poly-A tail added to 3' end, introns are removed, exons are joined together)

Question 44

Which of the following statements comparing prokaryotic and eukaryotic transcription is not true?

Answer 44

RNA polymerase requires a primer in bacteria; in eukaryotes , it does not

Question 45

The nontemplate strand of a portion of a gene reads 5'-TTCACTGGTTCA. What is the sequence of the resulting transcript for this portion?

Answer 45

5'-UUCACUGGUUCA