Q: If a cell spends 5 hours in G1, 7 hours in S, 3 hours in G2, and 1 hour in mitosis, what percentage of the cell cycle is spent in mitosis?

$$\frac{1}{16} \times 100\% = 6.25\%$$

Question 1

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes are inherited from each parent and may contain different alleles, while sister chromatids are identical copies formed during DNA replication.

Question 2

During which stage of the cell cycle does DNA replication occur?

Accepted Answer

S phase

Question 3

A diploid cell with $$2n = 8$$ undergoes mitosis. How many chromosomes will each daughter cell have after cytokinesis?

Accepted Answer

$$8$$

Question 4

Which of the following events occurs during Prophase I of meiosis but NOT during prophase of mitosis?

Accepted Answer

Synapsis and crossing over between homologous chromosomes

Question 5

If an organism has a haploid number of $$n = 6$$, how many different combinations of chromosomes are possible in its gametes due to independent assortment alone?

Accepted Answer

$$2^6 = 64$

Question 6

Which of the following best explains why meiosis I is called a 'reductional division'?

Accepted Answer

The number of chromosomes per cell is halved as homologous chromosomes separate.

Question 7

A mutation in a gene encoding a cyclin-dependent kinase (Cdk) results in a nonfunctional protein. Which cell cycle process is most directly affected?

Accepted Answer

Progression through cell cycle checkpoints

Question 8

Which of the following is NOT a source of genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of DNA during S phase

Question 9

In humans, oogenesis results in the formation of one ovum and polar bodies. Which process explains why only one functional gamete is produced?

Accepted Answer

Unequal cytokinesis during meiosis I and II

Question 10

A cell is observed with chromosomes aligned at the metaphase plate, each consisting of two sister chromatids. Which phase is this cell in?

Accepted Answer

Metaphase of mitosis

Question 11

Which of the following best describes the role of the synaptonemal complex during meiosis?

Accepted Answer

It facilitates the pairing and recombination of homologous chromosomes.

Question 12

If a cell spends 5 hours in G1, 7 hours in S, 3 hours in G2, and 1 hour in mitosis, what percentage of the cell cycle is spent in mitosis?

Accepted Answer

$$\frac{1}{16} 	imes 100\% = 6.25\%$$

Question 13

Which of the following is true regarding the products of meiosis II?

Accepted Answer

Each cell contains half the number of chromosomes as the original diploid cell, and chromosomes are single chromatids.

Question 14

A cell with a mutation that prevents crossing over during meiosis would most likely produce gametes that:

Accepted Answer

Are genetically identical except for independent assortment

Question 15

Which of the following best explains why mitosis does not contribute to genetic variation?

Accepted Answer

Mitosis does not involve crossing over or independent assortment.

Question 16

During which substage of Prophase I does crossing over occur?

Accepted Answer

Pachynema

Question 17

Which of the following statements about centromere position is correct?

Accepted Answer

Submetacentric chromosomes have the centromere between the middle and the end, creating p and q arms.

Question 18

A geneticist observes a cell with bivalents forming and chiasmata visible. Which stage is this cell most likely in?

Accepted Answer

Diplonema of Prophase I

Question 19

Which of the following is a key difference between spermatogenesis and oogenesis in humans?

Accepted Answer

Spermatogenesis produces four functional sperm cells, while oogenesis produces one functional ovum and polar bodies.

Mitosis and Meiosis: Chromosome Structure, Cell Cycle, and Genetic Variation

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