1. Mendelian Genetics How Genes Work

3. Who Are You? Phenotype – How you look; PHysical appearance Genotype – Your genetic makeup; GENEs

4. Modern genetics began with Gregor Mendel’s quantitative experiments with pea plants Father of Genetics Figure 9.2A, B Stamen Carpel

5. Mendel crossed pea plants that differed in certain characteristics and traced the traits from generation to generation Figure 9.2C This illustration shows his technique for cross-fertilization 1 Removed stamens from purple flower White Stamens Carpel Purple PARENTS (P) OFF- SPRING (F 1 ) 2 Transferred pollen from stamens of white flower to carpel of purple flower 3 Pollinated carpel matured into pod 4 Planted seeds from pod

6. Genetics Basics Chromosomes occur in pairs, one from MOM, one from DAD (homologues) Genes are carried on chromosomes Genes code for a trait or characteristic (I.e. hair color) Alternate forms of that trait are called ALLELES (ie. Blond, brown, redhead, etc)

7. Alleles… Alleles can be dominant or recessive Heterozygous vs. homozygous Only way to “see” a recessive trait?

8. Mendel ‘s basic laws Law of Segregation Law of Independent Assortment

9. The chromosomal basis of Mendel’s principles Figure 9.17

10. Walter Sutton’s Theory of Chromosomal Inheritance (Mendel’s proof) Gametes contribute to heredity via nuclear material (chromosomes) Homologues segregate during meiosis Homologues separate independently of other homologous pairs

11. Probability Mathmatical model of how often specific events will happen # of occurances/# of attempts

12. Punnett Square Visual representation or model of – what alleles can be present in gametes – how those alleles can recombine in offspring Used to determine the probability of offspring’s genetic makeup

13. Monohybrid Cross One gene – 2 alleles considered (one from mom, one from dad

14. Dihybrid Cross 2 genes – 4 alleles considered

16. How can we determine Homo- vs. heterozygous individuals? Test Cross – Must use homo recessive to conduct cross in order to “see” the questionable allele

17. What Mendel Didn’t See Multiple alleles Codominance Epistasis Polygenic traits or Continuous Variation Pleiotropy Incomplete Dominance or “blended inheritance” Environmental Effects Sex linked and sex influenced traits

18. CoDominance – Both alleles expressed at the same time; both dominant

19. Incomplete dominance: neither allele is fully dominant (blended inheritance) Figure 9.12Ax

20. Epistasis Sequential action of genes – Product of one gene influences another (one gene gives “permission” for another allele to work – Gene action acts as a biochemical pathway & feedback inhibition Ex: Indian corn coloration

21. Pleiotropy Where one allele may have multiple effects on phenotype –

22. Normal and sickle red blood cells Figure 9.14x1

23. Individual homozygous for sickle-cell allele Sickle-cell (abnormal) hemoglobin Abnormal hemoglobin crystallizes, causing red blood cells to become sickle-shaped Sickle cells Breakdown of red blood cells Clumping of cells and clogging of small blood vessels Accumulation of sickled cells in spleen Anemia Heart failure Pain and fever Brain damage Damage to other organs Spleen damage Kidney failure Rheumatism Pneumonia and other infections Paralysis Impaired mental function Physical weakness

24. Continuous Variation or Polygenic Traits Multiple genes acting to influence a characteristic – Produces gradual changes, not distinct “borders” Ie. Height, weight, nose length, skin pigment

25. Figure 9.16 P GENERATION F 1 GENERATION F 2 GENERATION aabbcc (very light) AABBCC (very dark) AaBbCc Sperm Fraction of population Skin pigmentation

26. Environmental Influence Example = color change of fur in arctic animals

27. Same eyes, different lighting

28. Multiple Alleles More than one allele per gene

29. 3 alleles (ABO) – 4 phenotypes (A, B, AB, O) Uses concept of glycoproteins (sugar name tags or antigens) to mark cells Non-recognition of the correct “name tag” for blood type can cause agglutination

30. Landsteiner Blood Groups Type A – galactosamine – AA (homo) or AO (hetero) Type B – galactose – BB or BO Type AB – galactosamine + galactose (codominant) Type O – no sugar marker - OO

31. Blood Donor Facts Universal DonorUniversal Recipient

32. Rh factor Rh factor can be + or – + is like a “seen” name tag or antigen - is “invisible” Rh- moms that have Rh+ babies are subject to spontaneous abortions – Erythroblastosis fetalis – Controlled with an injectionof RhoGam to “hide” babies cells

33. Sex Linked “Sex on the X” Specific trait/disorder is found on sex chromosome, usually the X Usually recessive traits Seen more often in males than females Ex: color blindness, hemophilia

35. Barr Body inactivation In females, both X chromosomes are not metabolically active Random inactivation of one X chromosome may influence traits expressed