PSYB20H3 Lecture Notes - Amnion, Twin, Lanugo
Document Summary
Each individual"s phenotype, or directly observable characteristics, is a product of both genotype and environment. Chromosomes, rod like structures within the cell nucleus, contain our hereditary endowment. Along their length are genes, segments of deoxyribonucleic acid (dna) that send instructions for making a rich assortment of proteins to the cell"s cytoplasm. Gametes, or sex cells, are produced through a cell division process called meiosis. Crossing over and chance assortment of chromosomes into gametes ensure that each gamete receives a unique set of genes from each parent. Once sperm and ovum unite, the resulting zygote starts to develop into a complex human being through cell duplication, or mitosis. If the fertilizing sperm carries an x chromosome, the child will be a girl; if it contains a y chromosome, a boy. If the alleles differ, the individual is heterozygous, and relationships between the alleles determine the phenotype.
