In egg production, only one of the four products of meiosis becomes an egg. In sperm production, all 4 products of meiosis become sperm. Everything of importance occurs in the first part of meiosis I, where chromosomes line up and exchange pieces, a process called crossing-over. Meiosis is only used for sexual reproduction. This process is used for growth and repair.
Genes are on chromosomes, and can come in alternate forms, called alleles.
I A and I B are codominant with respect to each other, and each is dominant to i. There are 6 genotypes, each of which makes one of 4 phenotypes. The basic pattern is that the body and its structures form while still very tiny, and then spends most of the pregnancy more or less just growing in size. Week 1- cleavage divisions, egg implants at end of week 1. Must produce chorionic gonadotropin to maintain endometrium.