Question

If a cell has one chromosome in excess of the normal number of chromosomes present in the nucleus, it is referred to as

• A. \( \text{aneuploid} \)
• B. \( \text{polyploid} \)
• C. \( \text{tetraploid} \)
• D. \( \text{Tetraploid} \)

Hint:

Aneuploidy: Change in number (\(2n \pm 1\)).
Polyploidy: Change in sets (\(3n, 4n, \dots\)).

Answer 1

The Correct Option is A

Concept: Numerical chromosomal aberrations occur when cells do not have the standard "Euploid" number of chromosomes.
• Polyploidy involves having extra sets of chromosomes (e.g., 3n, 4n).
• Aneuploidy involves having an abnormal number of individual chromosomes.

Step 1: Identifying Aneuploidy.
Aneuploidy occurs when an individual chromosome is either missing or present in excess. The condition where there is "one chromosome in excess" is specifically called Trisomy (\(2n + 1\)).

Step 2: Categorizing the term.
Since the change involves a single chromosome rather than an entire set, the correct general term is "aneuploid." Examples include Down Syndrome, where there is an extra copy of chromosome 21. Final Answer: A cell with one extra chromosome is referred to as an aneuploid cell.