Q: A scientist measures the DNA content of yeast cells at 24 fg and 48 fg. If 1 fg of DNA equals $$9.78 \times 10^5$ base pairs, how many base pairs are present in a haploid yeast genome?

$$2.35 \times 10^7$ (24 fg $$\times$$ 9.78$$ \times $$10^5)$$

Q: If a cell's DNA content increases from 24 fg to 48 fg during the S phase, what is the rate of DNA synthesis in base pairs per hour if the S phase lasts 2 hours?

$$1.17 \times 10^7$ base pairs/hour$$\ (24\ fg \times 9.78 \times $$10^5$$\ bp/fg \div 2\ hours)$$

Question 1

Which of the following events is unique to meiosis and does NOT occur during mitosis?

Accepted Answer

Alignment of homologous chromosome pairs at the metaphase plate

Question 2

During which stage of meiosis does crossing over occur, and what is its significance?

Accepted Answer

Prophase I; it increases genetic variation among gametes

Question 3

A yeast cell has a DNA content of 48 fg during a certain phase. According to the data, which phase is the cell most likely in?

Accepted Answer

G2 phase

Question 4

If a diploid cell with 2n = 8 chromosomes undergoes meiosis, how many chromosomes will each resulting gamete contain?

Accepted Answer

$$4$$

Question 5

Which of the following best explains why the four daughter cells produced by meiosis are genetically distinct from each other and from the parent cell?

Accepted Answer

Crossing over and independent assortment of chromosomes

Question 6

During an experiment, yeast cells are transferred to a nutrient-poor medium and their DNA content drops from 48 fg to 12 fg. What cellular process does this change most likely represent?

Accepted Answer

Completion of meiosis II

Question 7

Which protein complex is responsible for holding homologous chromosomes together during synapsis in prophase I?

Accepted Answer

Synaptonemal complex

Question 8

A scientist measures the DNA content of yeast cells at 24 fg and 48 fg. If 1 fg of DNA equals $$9.78 	imes 10^5$ base pairs, how many base pairs are present in a haploid yeast genome?

Accepted Answer

$$2.35 	imes 10^7$ (24 fg $$	imes$$ 9.78$$ 	imes $$10^5)$$

Question 9

Which of the following statements correctly compares the outcomes of mitosis and meiosis?

Accepted Answer

Mitosis produces two genetically identical diploid cells; meiosis produces four genetically diverse haploid cells

Question 10

Which event during meiosis is responsible for the formation of chiasmata?

Accepted Answer

Crossing over between non-sister chromatids during prophase I

Question 11

If a cell's DNA content increases from 24 fg to 48 fg during the S phase, what is the rate of DNA synthesis in base pairs per hour if the S phase lasts 2 hours?

Accepted Answer

$$1.17 	imes 10^7$ base pairs/hour$$\ (24\ fg 	imes 9.78 	imes $$10^5$$\ bp/fg \div 2\ hours)$$

Question 12

Which of the following best describes the role of meiosis in sexually reproducing organisms?

Accepted Answer

It reduces chromosome number by half and introduces genetic variability

Question 13

During which phase of meiosis are homologous chromosomes separated, and what is the result for chromosome number in the daughter cells?

Accepted Answer

Anaphase I; daughter cells become haploid

Question 14

Which mechanism ensures that sister chromatids are not genetically identical by the time they separate in meiosis II?

Accepted Answer

Crossing over during prophase I

Question 15

In the yeast DNA content experiment, which time point most likely corresponds to the completion of meiosis I?

Accepted Answer

7.5 hours (25 fg)

Question 16

Which of the following is a direct consequence of the release of cohesion along chromosome arms during anaphase I of meiosis?

Accepted Answer

Homologous chromosomes separate

Question 17

A mutation prevents the formation of the synaptonemal complex during meiosis. Which process would be most directly affected?

Accepted Answer

Crossing over between homologous chromosomes

Question 18

Which of the following best explains why meiosis, but not mitosis, is essential for sexual reproduction?

Accepted Answer

Meiosis reduces chromosome number, preventing chromosome doubling in offspring

Question 19

If a yeast cell at the end of meiosis II contains 12 fg of DNA, how many base pairs does this represent? (Use $$1\ fg = 9.78 	imes 10^5$ base pairs)

Accepted Answer

$$1.17 	imes 10^7$ base pairs

Question 20

Which of the following is NOT a mechanism by which meiosis increases genetic diversity?

Accepted Answer

Replication of DNA during interphase

Meiosis: Reduction of Chromosome Number and Genetic Variation

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