Inheritance: Genetic Variation

Understanding Genetic Variation

Genetic variation is the difference in DNA sequencing between individuals within a population.
Genetic variation is an important force in evolution as it allows natural selection to proceed.
There are several underlying causes of genetic variation including mutations, gene flow, random mating, and genetic drift.
A mutation is a change in the DNA sequence. Mutations might be caused by errors in DNA replication or repair, or by chemical or radiation damage.
Gene flow is the transfer of genetic variation from one population to another. If genes flow from one population to another, that can introduce new genetic variation to the receiving population.

Chromosomes and Genes

Chromosomes are structures found inside the nucleus of cells. They contain a single molecule of DNA tightly coiled many times around proteins called histones that support its structure.
Humans have 23 pairs of chromosomes, 22 pairs are autosomes, and one pair is sex chromosomes.
A gene is a segment of DNA on a chromosome that codes for a specific trait.
An allele is a variant form of a gene. Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome.

Role of Meiosis in Genetic Variation

Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell.
Meiosis introduces genetic variation via crossing over during prophase I and independent assortment of homologous chromosomes during metaphase I.
Crossing over is the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in the offspring.
Independent assortment during metaphase I leads to an unpredictable distribution of chromosomes in the gametes that will be produced.

Role of Sexual Reproduction in Genetic Variation

Sexual reproduction contributes to genetic variation in offsprings. The offsprings receive a mix of both parents’ genes.
During fertilisation, a sperm from the father fuses with an egg from the mother. The resulting cell, or zygote, combines the genetic material of the two parents, which leads to genetically distinct offspring.

Remember, understanding genetic variation is critical for understanding how life evolves and adapts to changes in the environment. Widespread instability in a given environmental factor can lead to either the flourishing or destruction of a species, depending upon how well they are genetically equipped to deal with these changes.