1. Law of Segregation alleles separate monohybrid cross Law of Independent assortment allele pairs inherited independently dihybrid cross

2. Rules of Multiplication & Additions Multiplication – likely that all events coincide Addition – sum of all possibilities

3. Co-dominance 2 alleles affect the phenotype in separate, distinguishable ways –ABO blood groups –3 alleles (MULTIPLE ALLELES) I A, I B, i both I A & I B are dominant to i allele I A & I B alleles are co-dominant to each other –determines presences of oligosaccharides on the surface of red blood cells

4. Polygenic inheritance Some phenotypes determined by additive effects of 2 or more genes on a single character –phenotypes on a continuum –human traits skin color height weight eye color intelligence behaviors

5. Albinism Johnny & Edgar Winter albino Africans

6. Nature vs. nurture Phenotype is controlled by both environment & genes Color of Hydrangea flowers is influenced by soil pH Human skin color is influenced by both genetics & environmental conditions Coat color in arctic fox influenced by heat sensitive alleles

7. Pleiotropy Most genes are pleiotropic –one gene affects more than one phenotypic character wide-ranging effects due to a single gene: dwarfism (achondroplasia) gigantism (acromegaly)

8. Acromegaly: André the Giant

9. Epistasis in Labrador retrievers 2 genes: E & B –pigment (E) or no pigment (e) –how dark pigment will be: black (B) to brown (b)

10. Incomplete dominance Heterozygotes show an intermediate phenotype –RR = red flowers –rr = white flowers –Rr = pink flowers make 50% less color

11. Dihybrid heterozygous cross

12. Chromosome theory of inheritance –experimental evidence from improved microscopy & animal breeding led us to a better understanding of chromosomes & genes beyond Mendel Drosophila studies It all started with a fly… A. H. Sturtevant in the Drosophila stockroom at Columbia University

13. Thomas Hunt Morgan embryologist at Columbia University –1 st to associate a specific gene with a specific chromosome –Drosophila breeding prolific 2 week generations 4 pairs of chromosomes XX=female, XY=male 1910 | 1933

14. Morgan’s first mutant… Wild type fly = red eyes Morgan discovered a mutant white-eyed male –traced the gene for eye color to a specific chromosome

15. Discovery of sex linkage red eye female white eye male x all red eye offspring 75% red eye female 25% white eye male x How is this possible? Sex-linked trait!

16. Genes on sex chromosomes Y chromosome –SRY: sex-determining region master regulator for maleness turns on genes for production of male hormones –pleiotropy! X chromosome –other traits beyond sex determination hemophilia Duchenne muscular dystrophy color-blind

17. Sex-linked traits Hh x HH XHXH Y male / sperm XHXH XhXh female / eggs XHXHXHXH XHYXHY XHXhXHXh XHXhXHXh XHYXHYXhYXhY XHXhXHXh XHXH XhXh XHYXHY Y XHXH XHXHXHXH XHYXHY XHXhXHXh XhYXhY sex-linked recessive

18. Sex-linked traits summary X-linked –follow the X chromosomes –males get their X from their mother –trait is never passed from father to son Y-linked –very few traits –only 26 genes –trait is only passed from father to son –females cannot inherit trait

19. Gene Recombination in Linked Genes In contrast, linked genes, genes located on the same chromosome, tend to move together through meiosis and fertilization. Under normal Mendelian genetic rules, we would not expect linked genes to recombine into assortments of alleles not found in the parents. –If the seed color and seed coat genes were linked, we would expect the F 1 offspring to produce only two types of gametes, YR and yr when the tetrads separate. –One homologous chromosome from a P generation parent carries the Y and R alleles on the same chromosome and the other homologous chromosome from the other P parent carries the y and r alleles.

20. Recombination Frequency # Recombinants Total Recombinants = Offspring that vary from parent phenotype. Conclusions: Genes are linked, but not entirely due to crossing over during meiosis.

21. Mechanisms of inheritance What causes dominance vs. recessive? –genes code for polypeptides –polypeptides are processed into proteins –proteins function as… enzymes structural proteins hormones

22. Prevalence of dominance Because an allele is dominant does not mean… –it is better –it is more common Polydactyly: dominant allele

23. Polydactyly individuals are born with extra fingers or toes dominant to the recessive allele for 5 digits recessive allele far more common than dominant  399 individuals out of 400 have only 5 digits  most people are homozygous recessive (aa)

24. Hound Dog Taylor

25. Other Genetic Diseases of Interest Blue People!Progeria

26. Chromosomal errors, I Nondisjunction: members of a pair of homologous chromosomes do not separate properly during meiosis I or sister chromatids fail to separate during meiosis II Aneuploidy: chromosome number is abnormal Monosomy~ missing chromosome Trisomy~ extra chromosome (Down syndrome) Polyploidy~ extra sets of chromosomes

27. Turners (XO) Kleinfelters (XXY) Down Syndrome Cri du Chat Chromosomal Abnormalities