Genetics Unit

1. Genetics Unit

2. Genetics = the field of biology devoted to understanding how characteristics are transmitted from parents to offspring Heredity = the transmission of characteristics from parents to offspring

3. Mendel - “father” of modern genetics = laid the groundwork - experimented with garden peas - looked for traits = specific characteristics

5. Mendel (cont) - P1 generation = parental generation - F1 generation = offspring of the parental generation - F2 generation = offspring of the F1 generation

7. Mendel (cont) Mendel’s 1st Law = Law of Segregation 1) Organisms inherit two copies of each gene, one from each parent 2) Organisms donate one copy of each gene in their gametes.

8. Mendel (cont) Mendel’s 2nd Law = Law of Independent Assortment 1) The presence of one trait does not affect the appearance of another trait

9. Basics of Genetics - Gene = a segment of DNA on a chromosome that controls a specific trait - because chromosomes come in pairs, genes come in pairs

10. Basics of Genetics (cont) - Allele = each of several forms of a gene - aka: letters - each allele has a specific location on a chromosome (= locus) - capital letters = dominant alleles - lowercase letters = recessive alleles

12. Basics of Genetics (cont) - Homozygous = both alleles are alike - homozygous dominant = both capital letters = BB - homozygous recessive = both lowercase letters = bb - Heterozygous = alleles are different = Bb

13. Polydactyly Polydactyly is the condition of having more than the typical number of fingers or toes. The allele for polydactyly is dominant.

14. Basics of Genetics (cont) - Genotype = genetic makeup of an organism - consists of alleles (letters) - Phenotype = the appearance of an organism as a result of its genotype - aka: what does it look like - human phenotype can be altered by behavior BB Green Eyes

15. Monohybrid Crosses = a cross between individuals that involves one pair of traits - Example: Black hair (B) in guinea pigs is dominant to brown hair (b)

16. Example 1:Homozygous Dominant X Homozygous Dominant B B Genotypic Ratio Phenotypic Ratio 4 BB : 0 Bb : 0 bb BB B BB BB BB B 4 Black : 0 Brown

17. Example 2:Homozygous Recessive X Homozygous Recessive b b Genotypic Ratio Phenotypic Ratio 0 BB : 0 Bb : 4 bb bb b bb bb bb b 0 Black : 4 Brown

18. Example 3:Homozygous Dominant X Heterozygous B B Genotypic Ratio Phenotypic Ratio 2 BB : 2 Bb : 0 bb BB B BB Bb Bb b 4 Black : 0 Brown

19. Example 4:Homozygous Recessive X Heterozygous b b Genotypic Ratio Phenotypic Ratio 0 BB : 2 Bb : 2 bb Bb B Bb bb bb b 2 Black : 2 Brown

20. Example 5:Heterozygous X Heterozygous B b Genotypic Ratio Phenotypic Ratio 1 BB : 2 Bb : 1 bb BB B Bb Bb bb b 3 Black : 1 Brown

21. Testcross = an individual of unknown genotype is crossed with a homozygous recessive individual - can be used to determine the genotype of any phenotype that is dominant

22. Example 6: Testcross b b Genotypic Ratio Phenotypic Ratio 0 BB : 2 Bb : 2 bb Bb B Bb bb bb b 2 Black : 2 Brown

23. Example 6: Testcross b b Genotypic Ratio Phenotypic Ratio 0 BB : 4 Bb : 0 bb Bb B Bb Bb Bb B 4 Black : 0 Brown

24. Example 6: Testcross b b Genotypic Ratio Phenotypic Ratio 0 BB : 0 Bb : 4 bb b bb bb bb bb b 0 Black : 4 Brown

25. Incomplete Dominance = the F1 Generation will have a phenotype in between that of the parents - Example: Red flowers (R) and White flowers (r) can make Pink flowers (Rr)

26. Example 7: Incomplete Dominance Pink Flower X Pink Flower R Genotypic Ratio Phenotypic Ratio r 1 RR : 2 Rr : 1 rr RR R Rr Rr rr 1 Red: 2 Pink : 1 White r

27. Example 7: Incomplete Dominance Pink Flower X Red Flower R r Genotypic Ratio Phenotypic Ratio 2 RR : 2 Rr : 0 rr RR R Rr RR Rr R 2 Red: 2 Pink : 0 White

28. Example 7: Incomplete Dominance White Flower X Red Flower Genotypic Ratio Phenotypic Ratio r r 0 RR : 4 Rr : 0 rr Rr R Rr Rr Rr R 0 Red: 4 Pink : 0 White

29. Example 7: Incomplete Dominance Pink Flower X White Flower R r Genotypic Ratio Phenotypic Ratio 0 RR : 2 Rr : 2 rr Rr r rr Rr rr 0 Red: 2 Pink : 2 White r

30. Codominance = when both alleles for a gene are expressed in a heterozygous offspring - Example: Red coat color (R) in horses is codominant with white coat color (R’) to make a horse with a mix of red and white coat color (RR’)

31. Example 8: Codominance Red Coat X White Coat R R Genotypic Ratio Phenotypic Ratio 0 RR : 0 R'R' : 4 RR' RR' RR' R' RR' RR' R' 0 Red Coat : 0 White Coat : 4 Red/White Coat

32. Example 8: Codominance Red/White Coat X White Coat R R' Genotypic Ratio Phenotypic Ratio 0 RR : 2 R'R' : 2 RR' RR' R'R' R' RR' R'R' R' 0 Red Coat : 2 White Coat : 2 Red/White Coat

33. Example 8: Codominance Red/White Coat X Red Coat R R' Genotypic Ratio Phenotypic Ratio 2 RR : 0 R'R' : 2 RR' RR RR' R RR RR' R 2 Red Coat : 0 White Coat : 2 Red/White Coat

34. Dihybrid Cross = a cross between individuals that involves two pairs of traits - Example: Black hair (B) in guinea pigs is dominant to brown hair (b) and rough coat (R) is dominant to smooth coat (r)

35. Example 1: Homozygous Dominant X Homozygous Recessive BBRR bbrr

36. Example 1: Homozygous Dominant X Homozygous Recessive BR BR BR BR BbRr BbRr BbRr BbRr br br BbRr BbRr BbRr BbRr br BbRr BbRr BbRr BbRr BbRr BbRr BbRr BbRr br

37. Example 2: Heterozygous X Heterozygous BbRr BbRr

38. Example 2: Heterozygous X Heterozygous BR Br bR br BBRR BBRr BbRR BbRr BR Br BBRr BBrr BbRr Bbrr bR BbRR BbRr bbRR bbRr Bbrr bbRr bbrr BbRr br