What generates variation in a species?

Question

What is the biological mechanism behind the variation within sexually reproducing species? Obviously, the children are combinations, to differing degrees, of their parents. But how does the variation originate in the parents to begin with?I'm not referring to evolution or mutations rather I have in mind things like facial structure and personality in humans, or fur coloring in dogs. I just thought I vaguely remembered there was some kind of driver of variation... For example, does the parent produce a variety of germ cells that purposely differ from the parent's geneome?I just think I'm missing something here.(I'm familiar with DNA and genetics having taken a biology class in college and remembering much of it, I just can't seem to put my finger on this point...)

Answer 1

Variation within a species is mainly generated through mutations and genetic recombination during sexual reproduction.

Mutations are random changes in DNA sequences. Most mutations are small and harmless, but some create new traits that can be passed to future generations. Mutations are the original source of all new genetic variation.

Another major source of variation is genetic recombination during meiosis. During meiosis, chromosomes from each parent exchange pieces of DNA through a process called crossing over. In addition, chromosomes are randomly distributed into egg and sperm cells through independent assortment. As a result, every offspring receives a unique combination of genes.

Fertilization also increases variation because each sperm and egg combination is random. This is why siblings can look similar but are never genetically identical (except identical twins).

A simple way to think about it:

1)Mutations create new genetic possibilities

2)Sexual reproduction shuffles those possibilities into new combinations