4 Chromosomes and Genes Each cell has 46 chromosomes = 23 pairs Genes give instructions to perform a certain functionTwo of this set are X and Y (the sex chromosomes) and the other 22 pairs guide the expression of other traits.
7 Behavior GeneticistsAsk questions about the extent that genetics plays on our differencesHeritability – statistical estimate of how much behavior is due to genes. Max value is 1.0
8 Twin StudiesIdentical Twins- develop from a single fertilized egg that splits in two, creating two genetically identical organismsFraternal Twins - develop from separate eggsgenetically no closer than brothers and sisters, but they share the fetal environment
9 Twins and heritability studies Bouchard – studied 100 twins raised apart and their IQ scoresThose raised apart = coefficient of .69 on IQ testThose raised together = .88Criticized = adopted parents have particular environment
10 Molecular GeneticsLooks at genes that can specifically cause disordersGender determined by 23rd chromosome pairMen = XY – means some recessive characteristics from mother not blocked (color blindness)Women = XX
11 Chromosomal Disorders Turner’s SyndromeSingle X on 23rd pairShortness, webbed necks, sterility
12 Chromosomal Disorders Klinefelter’s syndrome – XXY patternMales – less testosterone, weaker body, possible infertilityDown’s SyndromeExtra chromosome on the 21st pair
13 Geneticists can now test for some disorders in Utero Down’s syndromeTay-Sachs disease (death to nerve cells mental/physical deform. onsetSpina Bifida (one of most common in U.S. 1/1000 births – spinal)Looking for an increase in a protein or hormone in early pregnancy