Question

What are homologous chromosomes?

Answer 1

Hint: Chromosomes are thread-like structures which are located inside the nucleus of the cell and each of these chromosomes are made up of proteins and deoxyribonucleic acid (DNA) which is passed on from one generation to another.

Complete Answer:
Homologous chromosomes are defined as two pieces of DNA within an organism who is a diploid (2n) which carry the same genes one from each parent i.e. one from a father and one from the mother. This suggests that both parents contribute to the complete genome of an organism.

Humans have 23 pairs of chromosomes which makes 46 chromosomes in total. Each parent contributes 23 chromosomes which encode the same genes. Therefore, our cells have 46 chromosomes in which two copies of each chromosome is present.

Homologous chromosomes though code for the same genes but can have different versions of each gene which helps in creating variety and stabilise the population. It also decreases the harmful effects of mutations which can be lethal.

If two versions of the same protein are present in an organism, it can be beneficial as the other version might be a better one. This also creates or leads to different phenotypes among the same species and improves the variety of the population. The alleles of a gene can have a dominant or recessive effect and when a dominant allele is present it shows its characteristics. Other complex relationships between alleles are present too.

Homologous chromosomes also take part in the process called homologous recombination that occurs during the cell division meiosis. It is also called as crossing over between gametes in which the part of chromosomes gets exchanged when they are in close vicinity with one another.

As an organism gets mature and begins to produce gametes which are haploid, they combine with another haploid gamete from the other partner and fertilization occurs. This leads to a mixing of traits and a new variety of offspring with some similarity to their parents are formed.

Note: Homologous chromosomes recombination plays a vital role in genetic diversity and also helps in determining the unique gene profile of an individual.