Question

Anaphase promoting complex (APC) is a protein degradation machinery necessary for proper mitosis of animal cells. If APC is defective in a human cell, which of the following is expected to occur?

• A. Chromosomes will not condense
• B. Chromosomes will be fragmented
• C. Chromosomes will not segregate
• D. Recombination of chromosome arms will occur

Answer 1

The correct option is C

Chromosomes will not segregate

The correct option is C.

Explanation of correct option:

1. Anaphase promoting complex is an essential protein degradation machinery for proper mitosis of animal cells.
2. It also refers to the cyclosome.
3. It helps in separating chromatids during anaphase.
4. If APC is defective, then chromosomes will fail to segregate.
5. If chromosomes are not appropriately segregated, it may lead to conditions where extra chromosome/s copy is present in the cell.
6. Example- Down syndrome (trisomy of the 21^st chromosome).

Explanation of incorrect options:

Option A:

Chromosome condensation occurs at the prophase (after replication during the S phase).

Option B:

APC does not fragment chromosomes. Instead, they are segregated by APC.

Option D:

Recombination of chromosome arms occurs during the prophase of meiosis I.

Final answer:

If APC is defective in a human cell, chromosomes will not segregate.