Question

Aneuploidy describes a numerical change in part of the genome, usually from the dosage of a single chromosome. If a chromosome or segment is overrepresented, it is called-

• A. Hypoploid
• B. Alloploid
• C. Polyploid
• D. Hyperploid

Hint:

Remember the prefixes:
- Hyper- means "excess" or "above" (chromosome gain, e.g., \(2n+1\)).
- Hypo- means "deficient" or "below" (chromosome loss, e.g., \(2n-1\)).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Aneuploidy is a type of numerical chromosome mutation where an organism's chromosome number is not an exact multiple of the basic haploid set (\(n\)).
Instead, it involves the loss or gain of one or more individual chromosomes.

Step 3: Detailed Explanation:
Let us define the terms associated with changes in chromosome number:
1. Hyperploid: This refers to aneuploidy where one or more chromosomes or chromosomal segments are added or overrepresented.
Examples include:
- Trisomy (\(2n + 1\)): Having three copies of a specific chromosome instead of two.
- Tetrasomy (\(2n + 2\)): Having four copies of a specific chromosome.
2. Hypoploid: This refers to aneuploidy where one or more chromosomes are lost or underrepresented.
Examples include:
- Monosomy (\(2n - 1\)): Lacking one chromosome from a homologous pair.
- Nullisomy (\(2n - 2\)): Lacking both chromosomes of a homologous pair.
3. Polyploid: This describes a cell or organism with three or more complete sets of chromosomes (e.g., \(3n, 4n, 6n\)).
4. Alloploid: A polyploid organism with chromosome sets derived from two or more different ancestral species.
Because the question describes the overrepresentation of a chromosome or segment, the correct term is hyperploid.

Step 4: Final Answer:
An overrepresented chromosome or segment in aneuploidy is called hyperploid, matching Option (D).