1. Chapter 14 Mendel and the Gene Idea

2. Mendelian genetics Gregor Mendel – father of genetics Austrian monk pioneer in the field gardener at monastery

5. Mendel’s Laws 1) Law of Dominance and Recessiveness – when 2 different alleles are present, one masks, or covers up, another 2) Law of Segregation – alleles separate when gametes form 3) Law of Independent Assortment – one allele does not influence another ex: tall does not influence yellow

8. Probability Rule of Multiplication – probability that 2 or more independent events will occur simultaneously in some specific combination -take probability of each event and multiply together -ex: both coins landing heads up ½ x ½ = ¼ or Pp x Pp = pp

10. Probability Rule of Addition – probability of an event that can occur in 2 or more different ways - add separate probabilities - ex: heterozygote from Pp x Pp ¼ + ¼ = ½

11. Law of Incomplete Dominance – (Intermediate inheritance) - When 2 different alleles are present (heterozygous), an intermediate trait is expressed ex: red flowers x white flowers = pink flowers

14. Multiple Alleles - 3 or more alleles for 1 gene - ex: human blood groups phenotype genotype antigens antibodies A I A I A or I A I a A anti–B B I B I B or I B I b B anti–A AB I A I B A or B O ii neither A anti–A & nor B anti-B

17. Test cross

18. Pleitropy One gene = many effects ex: sickle cell anemia

21. Penetrance Proportion of individuals who show expected phenotype from their genotype - ex: neuroblastomas

22. Polygenic inheritance Many genes = one trait -ex: human skin color

24. Pedigree analysis

26. Human Genetic Disorders Cystic fibrosis Tay-Sachs Sickle-cell anemia Huntington’s chorea Duchenne’s Muscular Dystrophy Down Syndrome Achondroplasia

27. Preventive Testing for genetic disorders usu. done when risk is high 1) pedigree determination 2) fetal testing: a) amniocentesis – 14 th – 16 th wk. of pregnancy; needle inserted into uterus; 10 ml fluid extracted & karyotype done b) chorionic villi sampling – sm. Amt. of fetal tissue is suctioned off from embryonic membrane villi (chorion) which forms part of placenta, then karyotype (results in 24 hrs.) advantages: 24 hr results vs. several weeks ; 8-10 wks of pregnancy

29. Preventive c) ultrasound – soundwaves (noninvasive; no risk) d) fetoscopy – tube with viewing scope directly examines fetus 3) newborn screening – PKU test

30. Chapter 15 The Chromosomal Basis of Inheritance

31. Genes are located on chromosomes, the structures that undergo segregation & independent assortment

32. Thomas Hunt Morgan – 1 st one to associate specific genes with specific chromosomes - studies with fruit flies, Drosophila melanogaster 1) grow rapidly 2) require small amt. of space 3) few chromosomes & these are large 1 st to discover a sex-linked gene (white eyes) X-linked

34. Sex-linked traits Carried on sex chromosomes May be X-linked or Y-linked No Y-linked found thus far ex: red-green color blindness in humans

36. Recombination In unlinked genes, when 2 organisms produce offspring, the end result could be: parental types or recombinants (unlike either parent) Frequency of recombination – if ½ have different phenotype than the parent, we say there is a 50% frequency of recombination (maximum)

38. Recombination frequency Frequency of = # of recombinants recombination total # of offspring x 100

40. Gene mapping map units - number assigned to show relative distance between genes on chromosomes recombination frequency = # of map units ex: recombination frequency of 25% translates to 25 map units

43. Sex determination systems a) X-Y system -humans, mammals, some insects -sperm (X or Y) determines sex b) X-O system -grasshoppers, crickets, roaches, some insects (only 1 sex chromosome) -female XX male XO -sperm either contains X or O

44. Sex determination systems c) Z-W system -birds, some fishes, some insects (moths, butterflies) -Z & W used to avoid confusion with X-Y -female ZW male ZZ -egg determines sex d) haplo-diploid system – most bees, ants -no sex chromosome -females develop from fertilized eggs (2n) -males develop from unfertilized eggs (1n); fatherless

46. X-inactivation (in mammals) fur color in calico cats determined by X chromosome 1X orange fur, 1X black fur calico cats almost always female 2 X chromosomes inherited, but in embryonic development, 1 is almost completely inactivated (inactive X condenses to Barr body) selection of which X occurs ramdomly ex: in humans dev. of sweat glands (mosaicism) heterozygous female have patches of normal skin & patches lacking sweat glands

48. Aneuploidies abnormal number of chromosomes due to nondisjunction – failure of chromosomes to separate in anaphase 1) trisomy – 2n+1 having 3 chromosomes in a pair ex: Trisomy 21 (Down Syndrome) 2) monosomy – 2n-1 having only 1 chromosome in a pair ex: Turner Syndrome

50. Polyploidy having extra sets of chromosomes Triploidy (3n) ex: diploid egg fertilized Quatraploidy (4n) ex: 2n zygote may not divide -fairly common in plants; almost nonexistent in animals (appear more normal than aneuploids)

51. Karyotype

52. Chromosomal mutations 1) deletion – piece of chromosome is lost *most serious 2) duplication – extra piece of chromosome 3) inversion – piece of chromosome breaks off & reattaches in a different orientation 4) translocation – piece of chromosome breaks off & reattaches to a nonhomologous chromosome

53. Chromosome mutations

54. Genomic imprinting