No two people are genetically identical, except for identical twins. The main source of genetic variation among humans is a. new mutations that occurred in the preceding generation. b. genetic drift. c. the reshuffling of alleles in sexual reproduction. d. environmental effects.

Key Concepts

Genetic Variation

Genetic variation refers to the differences in DNA sequences among individuals within a population. This variation is crucial for evolution and adaptation, as it provides the raw material for natural selection. In humans, genetic variation arises from mutations, gene flow, and sexual reproduction, leading to diverse traits and characteristics.

Sexual Reproduction

Sexual reproduction is a biological process where two parents contribute genetic material to produce offspring. This process involves the combination of alleles from each parent, resulting in unique genetic combinations in the offspring. The reshuffling of alleles during meiosis and fertilization is a significant source of genetic diversity in sexually reproducing organisms.

Mutations

Mutations are changes in the DNA sequence that can occur due to various factors, including environmental influences or errors during DNA replication. While most mutations are neutral or harmful, some can confer advantages that enhance survival and reproduction. New mutations contribute to genetic variation, but they are not the primary source compared to the reshuffling of alleles during sexual reproduction.