Midterm 3

Question 1

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?

Answer 1

G2

Question 2

What does NOT occur during mitosis?

Answer 2

Replication of DNA

Question 3

The microtubule-organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle. Specifically, it is known as the _____.

Answer 3

centrosome

Question 4

The cytoplasm from which of the following Xenopus laevis egg cells would contain the most MPF (mitosis promoting factor)?

Answer 4

A mature egg arrested in M phase

Question 5

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

Answer 5

the degradation of cyclin

Question 6

If the Rb protein was inactivated, which of the following would occur?

Answer 6

S phase would be activated in the absence of growth factors

Question 7

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

Answer 7

length, centromere position, staining pattern, and traits coded for by their genes

Question 8

The egg of a fruit fly has 4 individual chromosomes. How many chromosomes are in a somatic (body) cell of a fruit fly?

Answer 8

8 chromosomes

Question 9

Crossing over normally takes place during which of the following processes?

Answer 9

Meiosis I

Question 10

Independent assortment of chromosomes occurs during _____.

Answer 10

Meiosis I only

Question 11

In meiosis, homologous chromosomes are separated during ________.

Answer 11

anaphase I

Question 12

Homologous pairs of chromosomes align opposite to each other at the equator of a cell during ________.

Answer 12

metaphase I of meiosis

Question 13

You have isolated a single cell from a diploid organism. Which of the following would indicate that the cell was at metaphase of meiosis II (and NOT metaphase of meiosis I)?

Answer 13

None of the chromosomes were homologous to each other.

Question 14

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? They have _____

Answer 14

half the number of chromosomes and one-fourth the amount of DNA.

Question 15

Which of the following occurs in meiosis but not in mitosis?

Answer 15

synapsis of chromosomes

Question 16

What makes sexually reproduced offspring genetically different from their parents?

Answer 16

genetic recombination during meiosis

Question 17

An advantage of asexual reproduction is that it _____

Answer 17

enables the species to rapidly colonize habitats that are favorable to that species

Question 18

A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple’s second child has extra digits. What is the probability that their next (third) child will have extra digits?

Answer 18

1/2

Question 19

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

Answer 19

8

Question 20

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently. If 1000 F2 offspring resulted from a dihybrid cross, approximately how many of them would you expect to have red, terminal flowers?

Answer 20

190