Genetic variation refers to the diversity in DNA sequences among individuals within a population, occurring in both germ cells (sperm and egg) and somatic cells (all other cells).
Genetic variations are caused by following factors:
I. Mutation:
• Definition: Sudden, permanent heritable changes.
• Types: Gene mutation (point mutation), chromosome structure mutation, chromosome number mutation.
• Effect: Alters phenotype, introducing variations.
II. Genetic Recombination:
• Process: Crossing over during gamete formation in sexually reproducing organisms.
• Outcome: Produces new genetic combinations, leading to phenotypic variations.
III. Gene Flow:
• Definition: Movement of genes into/out of a population.
• Modes: Migration, gamete dispersal, DNA segment transfer (transformation).
• Impact: Alters gene frequency, causing evolutionary changes.
IV. Genetic Drift:
• Definition: Random fluctuation in allele frequency due to chance.
Examples: Population reduction from natural disasters.
• Influence: Greater in smaller populations, contributing to evolutionary change.
V. Chromosomal Aberrations:
• Exposure to radiation or carcinogens can lead to DNA breakage, where the broken ends may recombine in configurations different from their original arrangement.
• Cause: Rearrangement of genes.
• Effect: Variations due to alterations in gene arrangement or sequence.