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.
Because the chromosomes of each parent undergo genetic recombination during meiosis, each gamete, and thus each zygote, will have a unique genetic blueprint encoded in its DNA. In other words, meiosis and sexual reproduction produce genetic variation. In meiosis, A cell undergoes reduction division and, a human cell which is of 46 chromosomes, forms 4 cells of 23 chromosomes each. During the union of Gametes, 23 chromosome from the father's sperm and 23 from mother's egg cell fuse to form a diploid zygote of 46 chromosomes, and later embryo. If this meiosis doesn't happen a child would be having 92 chromosomes which is impossible at all costs.