Fundamentals of Genetics

1. Fundamentals of Genetics

2. The History of Genetics Genetics- scientific study of heredity Trait - characteristic that can be passed from parents to offspring Patterns of Inheritance

3. Blending of Traits • Once accepted hypothesis • did not explain appearance of unexpected traits in offspring Oops…blond baby boy. Where did that come from?

4. Studied pea plants cross-fertilization - cross of 2 different plants; offspring receives different forms of genetic trait from each parent Gregor Mendel - 1860’s • self-fertilization- cross of the same plant; offspring receives genetic information from one parent only

5. Purebred- organism receives the same genetic traits from both of its parents • Hybrid - organism receives different forms of a genetic trait

6. Mendel’s Observations • Crossed two different purebreds (P generation = parent generation) • resulting offspring is F1 (1st filial) -offspring

7. crossed these, resulting in F2 (2nd filial) generation • Found that there were always two types of traits - Dominant and Recessive

8. Mendel’s Conclusions: • Disproved blending hypothesis • offspring receives one of two “factors” from each parent - “factors” are genes • genes - sections of a chromosome that code for a trait

9. Allele- distinct form of a gene

10. dominant allele - expressed when two different alleles are present; represented with a capital letter: A • recessive allele - form of a gene that is not expressed when paired with a dominant allele; represented with a lower case letter: a

11. Mendel is the Father of Modern Genetics Gregor Mendel

12. Cellular Basis of Inheritance • Chromosome Theory of Hereditystates that the material of inheritance is carried by the genes in the chromosomes

13. Genes represent traits • Genotype - genes that make up an organism • includes both genes in a homologous pair • Phenotype - outward expression of the trait

14. homozygous - two alleles are identical (AA or aa) • also known as purebred organism • heterozygous- two alleles are different (Aa) • also known as a hybrid organism

15. Mendel’s Laws • Law of Segregation - gene pairs separate when gametes form • one gamete carries one gene and the other carries the other gene

16. Law of Independent Assortment - gene pairs segregate into gametes randomly and independently of each other

17. Law of Dominance - dominant allele is expressed, recessive allele will be hidden unless in homozygous form

18. Genetics and Prediction

19. Predictions for One Trait • Probability - predict likelihood of an event or outcome “tails” “heads” • “Heads” is one possible outcome out of a total of 2 possible outcomes.

20. P p P P P p P p P p p p • Punnett square - grid for organizing genetic information • can be used to make predictions about a cross between two organisms • monohybrid cross - cross between two parents involving one trait

21. AA x aa (A = normal, a = albino) A A A a A a a A a A a a

22. Genotypic ratio = AA 0/4 or 0% Aa 4/4 or 100% aa 0/4 or 0% • Phenotypic ratio = Normal 4/4 or 100% Albino 0/4 or 0%

23. Predictions for Two Traits • Two trait cross – cross between two parents and two traits • Dihybrid cross - cross between two heterozygous parents • use a 4 X 4 punnett square • sixteen possible outcomes

24. HhTt x hhtt (H = long hair, h = short hair; T = tail, t = no tail) FOIL! Ht hT ht HT ht HhTt Hhtt hhTt hhtt Hhtt hhTt hhtt ht HhTt ht HhTt Hhtt hhTt hhtt ht HhTt Hhtt hhTt hhtt

25. Genotypic ratio = • HHTT 0/16 or 0% • HHTt 0/16 or 0% • HHtt 0/16 or 0% • HhTT 0/16 or 0% • HhTt 4/16 or ¼ or 25% • Hhtt 4/16 or ¼ or 25% • hhTT 0/16 or 0% • hhTt 4/16 or ¼ or 25% • hhtt 4/16 or ¼ or 25%

26. Phenotypic ratio: • 25% Long hair, tail • 25% Long hair, no tail • 25% short hair, tail • 25% short hair, no tail JK!

27. Test cross - breed an organism whose genotype is questionable with a homozygous recessive organism results determine genotype of questionable organism Test Cross G? GG or Gg then it’s Gg If all offspring gg X G? then it’s probably GG If any offspring

28. heterozygous offspring show a phenotype that is in-between the phenotypes of the two homozygous parents blending of traits color in snapdragons, hypercholestolemia, instead of white or red – color is pink Incomplete Dominance X

29. r w r rr rw w rw ww

30. Both alleles are expressed equally Ex. Sickle Cell Disease HA = normal HS = sickle both are dominant and equally expressed – both normal red blood cells and sickle-shaped blood cells present in heterozygote Codominance

31. Polygenic Trait (Epistasis) • Trait controlled by more than one gene • ex. Eye color

32. Multiple Alleles • Three or more alleles for a trait in a human population • ex. Blood types: IA, IB, i (type O) • Karl Landsteiner discovered antigens which are responsible for different blood types

33. IA - contains antigen A IB - contains antigen B IAIB - contains antigens for both A & B i - contains neither A nor B Multiple Alleles - Blood Types

34. Blood Groups

35. Universal donor: O Universal recipient: AB Dominant Trait in Blood Groups Rh antigen = named after Rhesus Monkey people who have the Rh antigen = Rh+ (positive) people who do not have it = Rh- (negative) Rh-, Rh+ person = positive

36. Pleiotropy • Single gene affects more than one trait • ex. Sickle cell anemia - effects include blood cell shape, anemia, weakness, brain damage, spleen damage, & heart damage

37. Phenotype is a combination of genetic and environmental influences, epigenetics Ex. Identical twins share the same DNA but may look and act differently Environmental Effects ex. Himalayan rabbit - fur color depends on body temperature – dark where cooler, white where warmer Yes, they are identical!

38. “Nature vs. Nurture” Issue studies have been done on identical twins that have been separated at birth Up to a 3 inch height difference observed in studies where twins were raised in two different countries/environments Issues in Biology VS • Twins raised in different adoptive homes showed similar interests and careers when they reconnected as adults