Final answer:
Crossing over during meiosis most contributes to genetic variation in a population.
Step-by-step explanation:
The process that most contributes to genetic variation in a population is A. crossing over during meiosis. This is because crossing over, or chromosomal crossover, represents a specific, non-random process where chromosomes are linked together and exchange DNA, contributing to the genetic diversity within a population. This process exchanges DNA between maternal and paternal chromosomes, creating unique genetic combinations in the resultant offspring. This genetic diversity is valuable for survival and adaptation, making sexual reproduction beneficial among organisms.This leads to a reciprocal exchange of equivalent DNA between a maternal chromosome and a paternal chromosome which increases the variance of genetic combinations in the haploid gamete cell.
During meiosis I, homologous chromosomes pair and exchange non-sister chromatid segments (crossover). This is followed by meiosis II, which is a division more similar to mitosis, where the chromatids separate and segregate into four haploid sex cells. However, due to the previous crossover, the resultant daughter cells do not contain identical genomes. This results in genetically unique offspring, which is beneficial for their survival and adaptation in various environments as it creates a mixture of traits from individual's parents. Hence, each gamete is unique. This is the main reason why sexual reproduction is the prevalent form of reproduction among organisms as it introduces significant genetic variation which is crucial for the survival and evolution of species.
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