Mitosis and Meiosis Questions and Answers

Answer: A

Prometaphase is sometimes named separately, between prophase and metaphase, for the period when the envelope has broken down but the chromosomes are not yet aligned. The mnemonic PMAT captures the sequence. Each stage is defined by what the chromosomes are doing at the time.

Answer: B

The metaphase plate is the imaginary plane on which they gather, held there by balanced pulling from both poles. Only when every chromosome is attached does the cell proceed. Alignment is checked before the chromatids are allowed to separate.

Answer: C

Once the cohesin holding them is cut they separate and move to opposite poles. From that moment each chromatid counts as a chromosome in its own right. The chromosome number of the cell therefore doubles briefly before division completes.

Answer: D

Separation is the point at which the count of chromosomes doubles, even though no new DNA has been made. This is why the chromosome number quoted for a cell depends on the stage it has reached. Counting centromeres rather than arms avoids the ambiguity.

Answer: A

The chromosomes also begin to decondense and the nucleolus reappears. Cytokinesis usually overlaps with this stage, dividing the cytoplasm as the nuclei re-form. The cell is then back in interphase with two nuclei separated.

Answer: B

Replication in S phase followed by one division gives daughters identical to the parent and to each other. Meiosis differs in both respects, halving the number and generating variation. Growth, repair and asexual reproduction all rely on mitosis.

Answer: C

One round of replication followed by two divisions halves the chromosome number, and crossing over with independent assortment makes each product distinct. This is the basis of sexual variation. No two gametes from one individual are likely to be identical.

Answer: D

Correct answer: 23

Meiosis halves the chromosome number, so a diploid cell with 46 gives four haploid products with 23 each. The halving happens at the first division, when homologous pairs are separated; the second division separates sister chromatids and keeps the number at 23. That reduction is what allows fertilisation to restore 46 rather than doubling it every generation.

Answer: A

Each of the 46 chromosomes consists of two sister chromatids at this stage, giving 92. Counting chromosomes and counting chromatids gives different answers, which is a frequent source of confusion. The DNA content is doubled even though the chromosome count is not.

Answer: B

Correct answer: False

S phase doubles the *DNA*, not the chromosome count. Each chromosome is replicated into two sister chromatids held together at the centromere, and while they remain joined they are counted as one chromosome. The number rises only at anaphase, when the centromeres separate and each chromatid becomes a chromosome in its own right - briefly doubling the count until the cell divides.