Genetics… …in the News

1. Genetics… …in the News

2. Chromosomal Mutations • Chromosome mutations are variations from the wild-type condition in... • chromosome number, • chromosome structure,

3. Karyotypes(viewing chromosomes) …the chromosome complement of a cell or individual, .. refers to the arrangement of metaphase chromosomes according to length,

4. Human Karyotypes Female Male

5. p 1 2 3 q Physical Maps(Cytological Maps) • AT versus GC rich regions stain differently, • i.e. Giesma stain, • in a very reproducible fashion. • Short arm “petit” (p), long arm (q), • #s refer to regions, with differential staining.

8. Chromosomal Mutations • chromosome number, • structure,

9. Aneuploidy ...the gain or loss of a single chromosome, • monosomy: the loss of a single chromosome, • trisomy: the gain of a single chromosome.

10. Meiotic Nondisjunction ...variation in chromosome number is caused by the failure of paired homologs to segregate properly during meiosis.

11. 2n = 46, if human We are following one pair of homologs. haploid gamete Disomic Normal Disjunction first division second division (gametes)

12. 2n = 46, if human We are following one pair of homologs. haploid gamete Trisomic Trisomic Monosomic Monosomic Nondisjunction First Division first division second division (gametes)

13. 2n = 46, if human We are following one pair of homologs. haploid gamete Disomic Disomic Trisomic Monosomic Nondisjunction Second Division first division second division (gametes)

14. 45, -5 Monosomy, 2n - 1 2n = 46 The loss of a single chromosome in an otherwise diploid cell.

15. C c a A B B C c Aa BB Cc Dd EE C CC Cc D d c Cc cc recessive lethal allele E E recessive lethal alleles monosomic Autosomal Monosomy • nearly always deleterious, usually lethal, • recessive lethal alleles are expressed, diploid

16. Trisomy, 2n + 1 2n = 46 47,+3 The gain of a single chromosome in an otherwise diploid cell.

17. A a a B B B C c c D d d E E E Autosomal Trisomy • generally deleterious, • usually changes the phenotype of the individual, trisomic

18. Trisomy in plants Jimsonweed(Datura stramonium)

19. Tomato

20. Down Syndrome (2n = 47, +21) Trisomy in Humans

21. Down Syndrome (2n = 47, +21) • occurs at a frequency of about 0.15%, • mental retardation (I.Q. 20 - 50), • mean life expectancy is about 17 years, • 47, +21 females are fertile, • trisomy 21 risk factors, maternal age.

22. Down Syndrome Trisomy in Humans

23. Down Syndrome Critical Genes • Chromosome 21 has about + 351 genes, • natural feedback mechanisms limit dosage effects of most of these genes, • It is estimated that the improper expression of approximately 20-40 genes produces the variety of phenotypes.

24. Maternal Age and Down Syndrome

25. Maternal Age? • in female humans*, oocytes arrest in Prophase I before birth, • meiosis continues upon menstruation, • thus, tetrad formation and cellular function must be maintained for decades. • and, as mother’s age increases, maternal detection of trisomy may be attenuated and spontaneous abortions drops. * Research may suggest otherwise.

26. Other Human Autosomal Trisomics • Edwards Syndrome (2n = 47, +18) • 0.0125% live births, • mental abnormalities, • “faunlike ears”, “rockerbottom feet”, small jaw, • nearly all die within several weeks of birth, • Patau Syndrome (2n = 47, +13), • 0.005% live births, • mental abnormalities, • cleft lip, small mal-formed head, “rockerbottom feet”, • mean life expectancy is about 130 days.

27. Autosomal Trisomy Causation • Age of Parents, • Random Errors, • or genetic predisposition, • Especially malfunction of recombination machinery, • crossing over and subsequent recombination are necessary for proper chromosome disjunction.

28. Sex Chromosome Monosomy • Turner Syndrome (2n = 45, X), • sometimes referred to as XO,

29. Turner Syndrome(2n = 45, X) • - 0.03% live female births, • - infertile, • - normal intelligence, • although specific • cognitive functions • may be affected.

30. Sex Chromosome Trisomy • Klinefelter Syndrome (2n = 47, XXY),

31. Klinefelter Syndrome (2n = 47, XXY) • - 0.1% - 0.2% live male births, • - infertile, • - mildly retarded. 48, XXXY; 48, XXYY; 49, XXXXY; 49, XXXYY

32. XXX Syndrome(2n = 47, XXX) • 47, XXX Syndrome, • 0.08 % female births, • typically normal development, • fertile.

33. XYY Syndrome(2n = 47, XYY) • 2n = 47, XYY Syndrome, • 0.10 % male births, • above average height, • sub-normal intelligence, • fertile. Genetic Disposition for Antisocial and Criminal Behavior? No.

34. 850,000 Live Births 150,000 Spontaneous Abortions 5165 Chromosomal Abnormalities 1849 (about 2:1 males) Sex Chromosome Aneuploid 1183 (20: 2: 1) Autosomal Trisomics 1,000,000 Conceptions

35. 850,000 Live Births 150,000 Spontaneous Abortions 75,000 Chromosome Mutations 39,000; Trisomics 13,500; XO 1,000,000 Conceptions

36. Aneuploidy Summary • Autosomal Monosomy, • nearly always deleterious, • Autosomal Trisomy, • usually deleterious, • trisomic individuals usually show distinct phenotypes, • Sex Chromosome Aneuploidy, • results in Turner or Klinefelter Syndromes, • 2n = 47, XXX, often normal, • 2n = 47, XYY, mild retardation, tall.

37. Chapter 5 • Do all of the practice questions (except 20).

38. Plant Biotechnology Information later in the Quarter

39. Chromosomal Mutations • Chromosome mutations are variations from the wild-type condition in... • chromosome number, • chromosome structure,

40. Polyploidy …more than two haploid sets of chromosomes are present, • 2n = diploid, • 3n = triploid, • 4n = tetraploid, • etc.

41. Polyploidy Generalitiesde novo • rare in most animal species, • known in lizards, fish and amphibians, • fairly common in plants, • odd numbers of ploidy are not usually maintained, • 3n, 5n, etc. • rarely found in organisms that rely on sexual propagation.

42. Autopolyploidy ...polyploidy resulting from the replication of one or more sets of chromosomes, …the additional set of chromosomes is identical to the normal haploid complement of that species.

43. added 2x 1x

44. Autopolyploidy …can be induced by treating cells with the drug colchicine, • colchicine: is a alkaloid derivative from the autumn crocus (Crocus veneris), ...inhibits microtubule polymerization, and thus inhibits the separation of chromosomes during meiosis. Crocus veneris …autumn crocus, …meadow saffron, …naked ladies.

45. Colchicine Treatment • 2n cells undergo S-phase, • no separation of chromosomes is accomplished, • no cell division occurs, • at telophase, the nuclear membrane reforms, • treatment for one cell cycle leads to 4n cells.

46. Natural Autopolyploidy • Heat, cold also affect microtubule polymerization and can lead to autopolyploidy.

47. Allopolyploidy …formed by the union of two or more distinct chromosome sets, ...i.e., from different species.

49. The Sad Tail of Raphanobrassica…Vegetable of the Proletariet? Cast Dr. G. Karpechenko, Russian Plant breeder, Brassica oleracea(2n = 18), - cabbage, large above ground food stock, ~value-less root, Raphanus sativus (2n = 18), - the common radish, large root food stock, ~value-less leaves.

50. n1 + n2 = 18 spontaneous autopolyploidy Super Vegetable? x Cabbage Radish 2n1 = 18 2n2 = 18 n1 = 9 n2 = 9 sterile 2n1 + 2n2 = 36