Question 1

Which of the following best describes the role of meiosis in the sexual life cycle, as shown in the first image?

Accepted Answer

Meiosis produces haploid gametes, ensuring chromosome number is halved before fertilization restores diploidy.

Question 2

During which phase of meiosis does crossing over occur, and what is its significance (refer to the second image)?

Accepted Answer

Crossing over occurs during Prophase I and increases genetic diversity by exchanging DNA between homologous chromosomes.

Question 3

Based on the third image, what is the principle of independent assortment and how does it contribute to genetic variation?

Accepted Answer

Independent assortment occurs during Metaphase I, allowing homologous chromosomes to align randomly, resulting in genetically unique gametes.

Question 4

Referencing the fourth image, what is the chromosome number in each daughter cell at the end of meiosis II if the original cell was diploid (2n = 4)?

Accepted Answer

$$n = 2$$

Question 5

What is nondisjunction, as illustrated in the fifth image, and what is a possible consequence if it occurs during Meiosis I?

Accepted Answer

Nondisjunction is the failure of homologous chromosomes to separate during Meiosis I, resulting in gametes with an abnormal number of chromosomes.

Question 6

The sixth image shows a karyotype with three copies of chromosome 21. What is the genetic condition, and what is the chromosomal basis for this disorder?

Accepted Answer

Down syndrome; trisomy of chromosome 21 due to nondisjunction.

Question 7

In the seventh image, what stage of cell division is depicted, and what is the chromosome composition of the resulting cells?

Accepted Answer

End of meiosis I; each cell is haploid but with duplicated chromosomes.

Question 8

A diploid organism has $$2n = 34$$ chromosomes. How many chromatids are present in a germ cell during the S phase of meiosis?

Accepted Answer

$$68$$

Question 9

If a mutation eliminated crossing over during meiosis, what would be the most likely outcome for the population?

Accepted Answer

Genetic diversity would decrease, as homologous chromosomes would not exchange genetic material.

Question 10

Why are siblings from the same parents genetically different from each other?

Accepted Answer

Because of crossing over, independent assortment, and random fertilization during sexual reproduction.

Question 11

Which of the following best explains why meiosis results in four non-identical daughter cells?

Accepted Answer

Meiosis involves two rounds of cell division and includes processes like crossing over and independent assortment.

Question 12

If nondisjunction occurs during Meiosis II, what is the expected chromosomal composition of the resulting gametes?

Accepted Answer

Half of the gametes will have the normal haploid number, one will have an extra chromosome, and one will lack a chromosome.

Question 13

Why does advanced maternal age increase the risk of nondisjunction during meiosis?

Accepted Answer

Older eggs are more likely to experience errors in chromosome separation due to prolonged arrest in meiosis.

Question 14

If an egg with 24 chromosomes (due to nondisjunction) is fertilized by a normal sperm with 23 chromosomes, what will be the chromosome number in the resulting zygote?

Accepted Answer

$$47$$

Question 15

Which of the following is a key difference between mitosis and meiosis?

Accepted Answer

Mitosis involves one division and produces identical diploid cells; meiosis involves two divisions and produces genetically diverse haploid cells.

Question 16

How does random fertilization further increase genetic diversity beyond the effects of independent assortment and crossing over?

Accepted Answer

It multiplies the possible combinations of chromosomes from both parents, resulting in a vast number of potential zygotes.

Question 17

Which event distinguishes Anaphase I from Anaphase II during meiosis?

Accepted Answer

In Anaphase I, homologous chromosomes separate; in Anaphase II, sister chromatids separate.

Question 18

Why does meiosis require two rounds of cell division?

Accepted Answer

To ensure the chromosome number is halved and to increase genetic diversity.

Question 19

If homologous chromosomes fail to separate during Anaphase I, what is the likely outcome for the resulting gametes?

Accepted Answer

Half will have an extra chromosome, and half will lack one.

Question 20

Why is Down syndrome (trisomy 21) more common than other autosomal trisomies such as trisomy 18 or 13?

Accepted Answer

Chromosome 21 is smaller and contains fewer genes, so trisomy 21 is more compatible with life.

Study Guide: Meiosis, Genetic Diversity, and Chromosome Disorders

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