PSYC 2076 Chapter : Chapter 3
Document Summary
Chapter 3 the start of life: genetics and prenatal development: earliest development: it starts with the gametes sex cells that form a new cell at conception. Whether you are a male or female depends on the presence or absence of certain chromosomes: sex chromosomes x-y. The male gametes or sperm cells in humans and other mammals are heterogametic - contain one of two types of sex chromosomes. The female gametes or eggs however, contain only the x sex chromosome and are homogamatic. The sperm cell determines the sex of an individual in this case. If a sperm cell containing an x chromosome fertilizes an egg, the resulting zygote will be xx or female. Less than 3% of human pregnancies produce more than one child. It is very rare for a pregnancy to produce more than 2 children; triplets, quadruplets, etc. , are usually the result of fertility treatments. These larger numbers can easily complicate a pregnancy.