PSY 220 Lecture Notes - Lecture 5: Twin, Zygote, Phenotype

• School: Stony Brook University
• Department: Psychology
• Course: PSY 220
• Professor: Levinson

Document Summary

There is genetic variation in a species. Some genes aid adaptation more than others do. Genes that aid their bearers in adapting their environment will be passed to future generations more frequently (natural selection) Siblings born at the same time two separate eggs and two separate sperm. Younger or older biological sibling: 50% on average (some more, some less) Dizygotic twin sibling: 50% on average (some more, some less) Genetics are affected by the environment or individual. Genotype all the genes a person inherits. Phenotype the observable expressions of genes (environment impacts phenotype) Huntington"s disease delayed and can be expressed at middle age. Genetics do not have a single gene cause. Most are much more complicated (height and weight). Hard to distinguish that a single gene caused the characteristics (cancer); polygenic (multiple-gene) transmission. Allele variant of a gene (homozygous or heterozygous) Most genetic disorders (sickle cell) are recessive. Recessive genes on x 23rd chromosome (sex chromosome.