Q.36 Homologus chromosomes containing identical gene sites along their length called:
l. Alleles
2. LOCI
3. Dialleles
4. Chiasmata
Homologous chromosomes containing identical gene sites along their length are called loci.
Option Analysis
1. Alleles: These are different versions or variants of a gene at the same locus on homologous chromosomes, such as A and a for eye color. They are not the sites themselves.
2. Loci: Correct answer—plural of “locus,” referring to the specific, fixed positions (gene sites) along homologous chromosomes where identical genes are located, despite potential allelic differences.
3. Dialleles: Not a standard biological term; may confuse with “diploid” or dual alleles, but unrelated to chromosome gene sites.
4. Chiasmata: These are the visible points of crossing over (genetic recombination) between non-sister chromatids of homologous chromosomes during meiosis prophase I, not gene sites.
Introduction
Homologous chromosomes containing identical gene sites along their length are defined by loci, the precise positions where matching genes reside—one from each parent. These paired structures (one maternal, one paternal) share length, centromere position, and loci but may differ in alleles, enabling genetic diversity via meiosis.
What Are Loci on Homologous Chromosomes?
Loci (singular: locus) mark fixed gene locations on chromosomes. Homologous pairs align at these sites during synapsis in prophase I of meiosis, forming a bivalent for proper segregation and recombination.
Key Chromosome Terms Comparison
| Term | Definition | Relation to Homologous Chromosomes |
|---|---|---|
| Alleles | Gene variants at a locus | Differ at same site (e.g., tall vs. short) |
| Loci | Identical gene positions | Matching sites along length |
| Dialleles | Non-standard term | Not applicable |
| Chiasmata | Crossover points | Form during meiosis pairing |
Functions in Genetics
Homologous chromosomes pair at loci for crossing over at chiasmata, promoting variation. Errors like nondisjunction disrupt this, causing aneuploidy (e.g., Down syndrome). Loci mapping aids gene linkage studies and inheritance patterns.
