PSYC 304 Chapter Notes - Chapter 2: Sickle-Cell Disease, Connective Tissue Disease, Genomic Imprinting
Document Summary
Human body is composed of trillions of cells that contain 23 chromosomes. Chromosomes hold genes, which are made up of dna. Sex cells (sperm and ova) reproduce through meiosis. Crossing over occurs in the cell, creating unique combinations of genes. Sex of the baby is determined by the sperm; all ova have an x chromosome, but a sperm can be either x or y. Twins occur in 1/30 births in the united states. Of twins conceived are dizygotic (fraternal). Occurs when more than one ovum is released and each is fertilized by a different sperm. Occurs when the zygote splits into two distinct separate, but identical, Recessive expressed only if paired with another recessive. If both are expressed, it"s incomplete dominance. Expression depends on whether the gene was inherited from the mother or the father. Many hereditary and chromosomal abnormalities can be diagnosed prenatally. Huntington"s: dominant, nervous system deteriorates, no cure. Pku: recessive, cannot break down phenylalanine, diet.
