Chromosomes and Genes Each cell has 46 chromosomes = 23 pairs Genes give instructions to perform a certain function Two of this set are X and Y (the sex chromosomes) and the other 22 pairs guide the expression of other traits.
Behavior Geneticists Ask questions about the extent that genetics plays on our differences Heritability – statistical estimate of how much behavior is due to genes. Max value is 1.0
Twin Studies Identical Twins- develop from a single fertilized egg that splits in two, creating two genetically identical organisms Fraternal Twins - develop from separate eggs genetically no closer than brothers and sisters, but they share the fetal environment
Twins and heritability studies Bouchard – studied 100 twins raised apart and their IQ scores Those raised apart = coefficient of.69 on IQ test Those raised together =.88 Criticized = adopted parents have particular environment
Molecular Genetics Looks at genes that can specifically cause disorders Gender determined by 23rd chromosome pair Men = XY – means some recessive characteristics from mother not blocked (color blindness) Women = XX
Chromosomal Disorders Turner’s Syndrome Single X on 23 rd pair Shortness, webbed necks, sterility
Chromosomal Disorders Klinefelter’s syndrome – XXY pattern Males – less testosterone, weaker body, possible infertility Down’s Syndrome Extra chromosome on the 21 st pair
Geneticists can now test for some disorders in Utero Down’s syndrome Tay-Sachs disease (death to nerve cells mental/physical deform. onset 6mo.-death @4) Spina Bifida (one of most common in U.S. 1/1000 births – spinal) Looking for an increase in a protein or hormone in early pregnancy