When babies are born, their brains contain about a hundred billion of neurons. However, a few of these brain cells are connected. At age three, there are one thousand trillion connections formed. The brain starts to cut off unused connections at the age of eleven.
Segregation of alleles happens when the pair of alleles of each parent separate and only one allele passes from each parent on to an offspring. So if you had heterozygous tall plants and mated them (Tt x Tt), they would each separate into T and t, allowing each offspring to get either a T or a t from each parent. The possible genotypes would be TT, Tt and tt.
