1. Chapter 3 - Genetics I.Structure Chromosomes in cell nuclei - 23 pairs/46 per cell 22 pairs = autosomes 1 pair = sex chromosomes

2. DNA - 1 long molecule - double-helix Gene - segment of DNA - gene pairs determine traits Allele - 1 member of gene pair - each parent gives 1 allele to child

3. II. Genetic Transmission of Characteristics 1 Gene/allele from each parent - 1 Brown or 1 blue from each parent Traits = Dominant v. Recessive Brown = dominant blue = recessive

4. Gene pairs = Homozygous or Heterozygous “same cell” “different cell” BB or bbBb Phenotype vs. Genotype Appearance vs. Genetic code

5. III. Transmission Types 1 Gene pair, Dominant trait - if even 1 allele for dominant trait, that trait will be exhibited (BB or Bb) - if parent is heterozygous, kids might not have trait

6. 1 Gene pair, Recessive trait - to exhibit trait, must have both recessive alleles (bb) - both parents must contribute recessive trait - if both parents exhibit (bb), all kids will - if both parents carry (Bb) 1 child doesn’t have (BB), 2 carry (Bb), 1 exhibits (bb)

7. Sex-linked traits - X determines more characteristics than Y - recessive x overridden by dominant X, not by Y - skews sex distribution of characteristics from recessive genes - so more boys exhibit, more girls carry - girl exhibits only if both parents have recessive x

8. Note: Sex-limited gene = on autosome, not sex chromosome - exerts effects more strongly in 1 sex than the other - hormones

9. IV. Polygenetic Research Polygenetic traits - most traits involve multiple genes + the environment - so most are on a continuum

10. Three types of studies – all are consanguinity/concordance Family Twin Adoption

11. Family Study - the more closely related people are the more genes they share, the more similar they will be - 50% shared between siblings & parent/child - 25% between grandparents, aunts/uncles - 0% between unrelated people

12. Problem - those who are more closely related are more likely to share environment

13. Twin Study - identical vs. fraternal twins MZ DZ - special environment of twinness - difference = amount of genes shared

14. MZ/identical = 100% shared genes DZ/fraternal = 50% shared genes If MZ = more similar than DZ, genetic evidence

15. Problem - MZ also more likely to share environment & be treated the same

16. MZ together vs. MZ apart

17. Adoption Study - adopted children share only genes with biological parents - share only environment with adoptive parents - if more similar to biological parents, evidence for genetic influence

18. Problem - Adoptive homes often similar to biological homes

19. V. Chromosomal Abnormalities Types: Abnormal number vs. structure

20. Abnormal number - problems with more or less than 46 Down syndrome (Trisomy 21) - 1 in 600 births - additional 21 st autosome - genetic but not inherited

21. Turner’s syndrome - 1 in 3000 female birthsXO - females with only 1 X chromosome Klinefelter’s syndrome - 1 in 500 male births - males with 1+ extra X chromosome(s) XXY

22. XYY complement - Supermale Syndrome - 1 in 1000 male births - males with 1+ extra Y chromosome(s) XYY Superfemale Syndrome - 1 in 1000 female births - females with 1+ extra X chromosome(s) XXX

23. Abnormal structure Fragile X syndrome - 1 in 2000 births - long arm of X breaks - recessive - males - MR - prevention: folic acid

24. VI. Genetic Testing 5 Methods Preimplantation - one cell from embryo

25. Amniocentesis - extracts amniotic fluid - after 16th week Chorionic Villus Sampling (CVS) - extract tissue from chorion (membrane surrounding fetus) - 7 th /8 th week

26. Quadruple screen - test mother’s blood for 4 proteins/hormones (Alpha-feto protein, HCG, Estriol & Inhibin) - high = neural tube defect or multiple fetuses - low = Down syndrome Targeted ultrasound - gross abnormalities - heart & neural tube abnormalities - proportions can indicate Down

27. What can you screen for? Diseases Fragile X Down Syndrome Pharmacogenomics Behavioral traits?

28. Genetics and Ethics Genetic determinism - polygenetic nature of most traits - role of environment - too complex to isolate single gene

29. Cloning - identical twins - clones … original (brain connections determined by experience)

30. Eugenics (“good genes”) - from evolution - in Britain and U.S. - laws preventing marriage of “feebleminded” - immigration restrictions - included forced sterilization - Carrie Buck (1928)