Which is a homologous chromosome pair? A) chromatid B) zygote C) gamete D) tetrad
The Correct Answer and Explanation is:
Correct Answer: D) Tetrad
A homologous chromosome pair refers to two chromosomes, one from each parent, that have the same length, gene position, and centromere location. These chromosomes carry the same types of genes in the same order but may carry different versions or alleles of those genes.
A tetrad is the best example of a homologous chromosome pair. It is a structure formed during prophase I of meiosis, where each chromosome has already replicated into two sister chromatids. When two homologous chromosomes pair up, each consisting of two chromatids, they form a group of four chromatids in total, which is called a tetrad. This is the phase where crossing over or genetic recombination can occur, which increases genetic diversity.
Let’s consider why the other choices are incorrect:
- A) Chromatid refers to one of the two identical halves of a duplicated chromosome. A chromatid is not a pair, so it cannot be a homologous chromosome pair.
- B) Zygote is a single cell formed by the union of a sperm and an egg. It contains chromosomes from both parents but is not itself a chromosome pair.
- C) Gamete is a reproductive cell (sperm or egg) that contains half the number of chromosomes of a normal body cell. Gametes carry only one chromosome from each homologous pair and are not themselves chromosome pairs.
Therefore, only D) Tetrad accurately represents a homologous chromosome pair because it includes both chromosomes of a homologous pair as they align during meiosis. The formation of tetrads is a key step in the production of genetically unique gametes, which is essential for sexual reproduction and evolutionary diversity.
