Extra credit problem for Lecture #4

1. Extra credit problem for Lecture #4 An agouti mouse is crossed to a white mouse and all the F1 offspring are agouti. An F1 female is crossed to an F1 male, and the offspring are: 11 agouti: 5 white: 4 black Q: Test the hypothesis that the original parental genotypes were BBCC and bbcc. Give the c2 value, the df, the P value, and state whether or not you reject the hypothesis.

2. Cytogenetics: Chromosome Mutations, Aberrations & Evolution

4. Chromosomes Prokaryote Eukaryote 4.2 X 106 base pairs Has 1000x more DNA DNA essentially naked DNA complexed w/ RNA & protein mRNA translated as mRNA is transcribed in nucleus, it's transcribed translated in the cytoplasm mRNA is often polycistronic mRNA is almost never polycistronic

5. Eukaryotic chromosomes

6. Metacentric Submetacentric Acrocentric

8. Human karyotype Sister chromatids Homologous pair Sex chromosomes autosomes

10. Why do we care? Many diseases and birth defects are a direct result of missing, broken, or extra chromosomes. • Down Syndrome • Cri du chat Syndrome • Patau Syndrome

11. Mutations at the level of the homologous pair • EUPLOIDY: "true" ploidy, meaning two members of each homologous pair. • ANEUPLOIDY: "not true" ploidy, meaning more or fewer members than two of each homologous pair. • MONOSOMY - one homolog; partner is missing • TRISOMY - three homologs • NULLISOMY- one entire homologous pair is missing.

12. Monosomy and Trisomy

13. Down Syndrome

16. How does it happen? Nondisjunction Each chrom. has two chromatids

17. Trisomy: Patau Syndrome • 1/20,000 births • severe mental retardation • heart and organ defects • polydactyly • death by the age of one year

19. Structural Changes • Deletions (deficiencies) • Duplications • Inversions • Translocations

20. Psuedo- dominance Homozygotes lethal Deletions (deficiencies) w

21. How can chromosomes break? Ionizing radiation (production of free radicals, which act like little atomic "cannon balls", blasting through strands of DNA or c'somes. Chemical insult. Why do they rejoin? Break points of chromosomes are highly reactive ("sticky"), whereas normal ends of c'somes are capped by telomeres, which do not readily bond to other molecules.

22. S Phase • Breaks that occur before S phase will affect both newly formed chromatids, & all daughter cells arising from them. • Breaks that occur when the chromosome is in dyad form may affect only one chromatid. (Thereafter, only the progeny carrying the broken chromatid will be affected.) Dyad

23. 1/50,000 births Deletion short arm chrom 5 Mental retardation Slow motor skill development Low birth weight and slow growth Small head (microcephaly) Partial webbing of fingers or toes Wide-set eyes (hypertelorism) High-pitched cry Cri-du-chat Syndrome

24. Structural Changes • Deletions (deficiencies) • Duplications • Inversions • Translocations

25. Duplications Duplication is a source of new genes over evolutionary time: e.g., gene families like globins and MHC genes

26. Bar eye: caused by duplication

27. Ribosomal DNA Globins (alpha and beta) Homeobox genes Duplications: source of evolutionary novelty?

28. Structural Changes • Deletions (deficiencies) • Duplications • Inversions • Translocations

29. Inversions