Infant development experts say that teething usually starts when your baby is around four months old, and continues until he or she is about two years old, at which time you get a reprieve until about five years old when the baby teeth start being replaced by grown-up teeth.
Quick Answer. Meiosis contributes to genetic variation by creating new groups of genes, according to the University of Miami Miller School of Medicine. The new groups are created when chromosomes passed down from a mother and father share instructions encoded into genes.
Meiosis is necessary for sexual reproduction, which allows for greater genetic variation in a species. Single-celled organisms that reproduce by mitosis produce two identical daughter cells. Genetic variation only occurs by spontaneous mutations in the organism. By contrast, organisms that reproduce using sexual reproduction combine two sets of genetic material, one from the male and one from the female, to form offspring that are genetically distinct from their parents.