Q11. Which phase of the cell cycle immediately precedes mitosis?
a) G1 phase
b) S phase
c) G2 phase
d) M phase
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Correct Answer: c) G2 phase
Explanation: The G2 phase, or gap 2 phase, precedes mitosis in the cell cycle. During G2 phase, the cell continues to grow and prepares for mitosis by synthesizing necessary proteins and organelles. Additionally, the DNA is checked for any errors or damage before entering mitosis.
Q12. Which of the following is true regarding daughter cells produced in mitosis?
a) They have half the number of chromosomes as the parent cell.
b) They are genetically identical to each other and to the parent cell.
c) They undergo crossing over during cell division.
d) They are only produced in gamete formation.
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Correct Answer: b) They are genetically identical to each other and to the parent cell.
Explanation: Mitosis results in the production of two daughter cells that are genetically identical to each other and to the parent cell. This is achieved through the equal distribution of replicated chromosomes during cell division.
Q13. During which phase of mitosis do the chromatids separate and move towards opposite poles of the cell?
a) Prophase
b) Metaphase
c) Anaphase
d) Telophase
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Correct Answer: c) Anaphase
Explanation: Anaphase is the stage of mitosis where the chromatids separate and move towards opposite poles of the cell. This separation is facilitated by the shortening of spindle fibers, ensuring that each daughter cell receives a complete set of chromosomes.
Q14. How many chromosomes are present in a human somatic cell undergoing mitosis?
a) 23
b) 46
c) 92
d) 69
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Correct Answer: b) 46
Explanation: Human somatic cells typically contain 46 chromosomes arranged as 23 pairs. During mitosis, each replicated chromosome consists of two sister chromatids, resulting in a total of 46 chromatids that segregate equally between the two daughter cells.
Q15. In which phase of meiosis does the nuclear envelope re-form around the separated chromosomes?
a) Prophase I
b) Metaphase I
c) Anaphase I
d) Telophase I
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Correct Answer: d) Telophase I
Explanation: Telophase I is the stage of meiosis where the nuclear envelope re-forms around the separated sets of chromosomes, marking the end of the first division. However, unlike mitosis, the chromosomes may or may not fully decondense during telophase I.
Q16. Which of the following is a characteristic of meiosis but not mitosis?
a) Production of genetically identical daughter cells
b) Occurs in somatic cells
c) Involves only one division
d) Results in the formation of gametes
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Correct Answer: d) Results in the formation of gametes
Explanation: Meiosis specifically occurs in germ cells (cells that give rise to gametes) and results in the formation of gametes, such as sperm and egg cells. Unlike mitosis, which produces genetically identical daughter cells, meiosis involves two divisions and leads to the formation of haploid cells with unique genetic combinations.
Q17. What is the main purpose of meiosis?
a) Growth and repair of tissues
b) Asexual reproduction
c) Formation of genetically diverse gametes
d) Maintenance of genetic stability
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Correct Answer: c) Formation of genetically diverse gametes
Explanation: Meiosis is primarily responsible for producing gametes with genetic diversity. This genetic variation arises from processes such as crossing over and random assortment of homologous chromosomes during meiosis I and random fertilization during sexual reproduction.
Q18. Which of the following events occurs during prophase II of meiosis?
a) Synapsis and crossing over
b) Separation of homologous chromosomes
c) Condensation of chromosomes
d) Formation of the spindle apparatus
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Correct Answer: c) Condensation of chromosomes
Explanation: Prophase II of meiosis is characterized by the condensation of chromosomes, similar to prophase of mitosis. During this phase, the nuclear envelope breaks down, and spindle fibers begin to form, preparing for the separation of sister chromatids.
Q19. In which phase of meiosis does the chromosome number reduce from diploid to haploid?
a) Prophase I
b) Metaphase I
c) Anaphase I
d) Telophase I
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Correct Answer: c) Anaphase I
Explanation: Anaphase I is the stage of meiosis where homologous chromosomes separate and move towards opposite poles of the cell. This reduction in chromosome number from diploid (2n) to haploid (n) occurs during anaphase I and is essential for the production of haploid gametes.
Q20. Which of the following events occurs during metaphase II of meiosis?
a) Homologous chromosomes pair up along the equatorial plane
b) Sister chromatids separate and move towards opposite poles
c) Synapsis and crossing over
d) Nuclear envelope reforms around the separated chromosomes
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Correct Answer: b) Sister chromatids separate and move towards opposite poles
Explanation: Metaphase II of meiosis is similar to metaphase of mitosis, where chromosomes align along the equatorial plane of the cell. However, in metaphase II, the aligned chromosomes are composed of sister chromatids, which separate and move towards opposite poles during anaphase II.