Question

what are three sources of genetic variation?
a genotypes, phenotypes, and polygenic traits
b sexual reproduction, crossing over, and mutations
c acquired traits, sexual reproduction, and mutations
d single - gene traits, polygenic traits, and adaptive traits

Explanation:

• Option A: Genotypes and phenotypes are not sources of genetic variation. Genotypes are the genetic makeup, and phenotypes are the observable traits. Polygenic traits are traits controlled by multiple genes, not a source of variation.
• Option B: Sexual reproduction combines genetic material from two parents. Crossing - over during meiosis (a part of sexual reproduction in eukaryotes) exchanges genetic segments between homologous chromosomes. Mutations are changes in the DNA sequence, all of which contribute to genetic variation.
• Option C: Acquired traits (like a muscle - builder's strong muscles) are not passed on genetically and thus not a source of genetic variation.
• Option D: Single - gene traits and polygenic traits are types of traits based on the number of genes controlling them. Adaptive traits are traits that help an organism survive in its environment, not a source of variation.

Answer:

B. sexual reproduction, crossing over, and mutations