Write short notes on Homologous Chromosomes

Subject: Zoology

Difficulty Level: Moderate
Homologous Chromosomes
Sex Determination

Updated by: Arabinda Naik

Answer:

Homologous chromosomes


A homologous chromosome pertains to one of a pair of chromosomes with the same gene sequence, loci, chromosomal length, and centromere location. A homologous pair consists of one paternal and one maternal chromosome. In humans, there are a total of 46 chromosomes in the nucleus of a somatic cell. Half of them (22 autosomes + X or Y chromosome) are inherited from the father and the other half (22 autosomes + X chromosome), from the mother. Each maternal chromosome has a corresponding paternal chromosome; they pair up during meiosis. Typically, a female will have 23 homologous chromosomes whereas a male will have 22. That is because the sex chromosomes, X and Y, in males are not homologous. The pairing up of homologous chromosomes during meiosis is important to promote genetic variation. Because of the genetic recombination that occurs between homologous pairs at meiosis, the resulting haploid gametes contain chromosomes that are genetically different from each other. 
In a simple way if we say, Humans are the perfect example of homologous chromosomes. As humans reproduce through sexual mode of reproduction where crossing over of chromosomes or genes takes place as a result one chromosome from father and another from mother is inherited into the offspring body. These chromosomes are carried in the haploid gamete cells, that is sperm and eggs.

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