Genetics

1. Genetics Explaining Inheritance

2. Early Ideas- Unilateral Inheritance Spermists Ovists

3. Early Ideas- Blending Green Blue + Yellow

4. Traits Skipping Generations Generation 1 Generation 2 Generation 3

5. Gregor Mendel 1822-1884 • Austrian Monk • Research in monastery garden • Garden pea

6. Characters & Traits Seed Shape Flower Position Seed Color Flower Color Stem Length Pod Color

7. Pea Anatomy • Naturally self-fertilizing • Experimental cross: • Remove anthers • Dust stigma with pollen

8. Hybrid seed Plants grown from hybrid seed produce green and yellow seed Inheritance of seed color Pollen from stock pure-breeding for yellow seed Dust on stigma of plant from stock pure-breeding for green seed P cross F1 F2

9. Quantitative Analysis 3.01:1

10. F2 Ratios Seed Shape 2.96 : 1 Flower Position 3.14 : 1 Seed Color 3.01 : 1 Flower Color 3.15 : 1 Stem Length 2.84 : 1 Pod Color 2.82 : 1

11. Mendel’s Explanation • Characters controlled by two “factors” • These segregate during reproduction • One factor is dominant, the other is recessive Y = factor for yellow seed color y = factor for green seed color

12. Pollen from stock pure-breeding for yellow seed Dust on stigma of plant from stock pure-breeding for green seed Y y cross Inheritance of seed color P F1 Yy Yy Yy Yy Yy Hybrid seed Yellow Dominant Plants grown from hybrid seed produce green and yellow seed F2 yy yy ? ? ? ? ? Green Recessive

13. X Y_ yy X Y_ yy Test Cross Phenotype = Genotype = ??? Unknown is YY Unknown is Yy

14. Ova from hybrid plant Y y y Y Pollen from hybrid plant Punnett Square ½ ½ 3 .. 1 YY ¼ Yy ¼ ½ Yy ¼ yy ¼ ½

15. Useful Terms: • Phenotype- • Outward appearance • e.g. yellow, green • Genotype- • Genetic makeup • e.g. YY, Yy, yy • Homozygous- YY or yy • Heterozygous-Yy

16. Seed Color Seed Shape Monohybrid Cross Dihybrid Cross Follow inheritance of one character Follow inheritance of two characters rr RR, Rr

17. rY Ry F1 Hybrid seed Plants grown from hybrid seed produce: F2 Dihybrid Cross Pollen from stock pure-breeding for wrinkled, yellow seed Dust on stigma of plant from stock pure-breeding for round, green seed P cross RrYy Four types of seed! Genetic Recombination

18. ¾ ¾ ¾ ¼ ¼ ¼ 9:3:3:1 ratio of phenotypes in F2 Seed Color Seed Shape ¾ X ¾ = 9/16 ¾ X ¼ = 3/16 ¼ X ¾ = 3/16 ¼ X ¼ = 1/16

19. ¾ ¾ Yellow ¾ ¾ ¼ ¼ ¼ ¼ Green Independent Assortment Seed Color Seed Shape ¾ X ¾ = 9/16 ¾ X ¼ = 3/16 ¼ X ¾ = 3/16 ¼ X ¼ = 1/16

20. ¾ ¾ Round ¾ ¾ ¼ ¼ ¼ ¼ Wrinkled Independent Assortment Seed Color Seed Shape ¾ X ¾ = 9/16 ¾ X ¼ = 3/16 ¼ X ¾ = 3/16 ¼ X ¼ = 1/16

21. Simple Dominance

22. (W)Widows Peak vs. Straight (w)

23. (F)Free Earlobe vs. Attached (f)

24. (E)Wet ear wax vs. Dry ear wax (e)

25. Six-digits (F)

26. Cleft chin (C)

27. Tongue Roll (T), non-rolling (t)

28. Hitchhiker’s Thumb (H)

30. Incomplete Dominance Four-o’clocks

31. An intermediate phenotype is shown

32. Incomplete Dominance • Three Shades: • Dark = DD • Medium = DL • Light =LL

33. Co-dominance - Both alleles can be expressed • For example, red cows crossed with white will generate roan cows. Roan refers to cows that have red coats with white blotches. • One allele of the gene codes for an enzyme that functions in the production of the red color. The other allele codes for the gene to make white color. If both alleles are present, both are expressed, resulting in a cow that has some red and some white.

34. Co-dominance • Andalusian Fowl also show this pattern of inheritance. • If you cross a black (BB) rooster • With a white (WW) chicken • You get black+white speckled (BW) offspring

35. Incomplete Dominance vs. Co-Dominance • Red and White Camellia • Red and White Snapdragons

36. X-Linked Traits • A carrier female • A normal male

37. X-Linked Traits • Some genes are located on the X chromosome. Females receive two alleles for these genes, but males only receive one. • In humans, hemophilia and color blindness are sex-linked traits. • When doing a Punnet square, use large X's and Y's to denote male and female, use superscript letters to designate the alleles. • If the parent is a male, the genotype is automatically known. A colorblind male has to be b, since he only has one allele and colorblindness is recessive. A normal male must then be B • Females can be heterozygous for the colorblindness trait - they are called carriers. A female can be BB - normal, Bb - carrier, or bb - colorblind

38. Multiple Alleles

41. Multiple Alleles • The black locus of Tribolium bC bC bC lethal bC_ black bST bST bST blackbST_ black b bb black bb+ red bt bt bt brown bt b+ red b+ b+ b+ red

42. Gene: Locus & Allele • Locus- place on a chromosome, responsible for a character, e.g. seed color • Allele- version of a locus, responsible for a trait, e.g. yellow or green

43. Pleiotropy Locus affects more than one character • bST color and lethality • Antenna bifurcata (ab) • antenna shape & male sterility

44. Epistasis

45. Four Phenotypes R_Y_ = Red R_yy = Brown rrY_ = Yellow rryy = Green Epistasis • Interaction of alleles at two loci: Locus 1 R = Red pigment r = yellow pigment Locus 2 Y = no chlorophyll y = chlorophyll

46. Epistasis rrYY RRyy RrYy R_Y_ rrY_ R_yy rryy

48. Explain the function of each allele:B b C c

50. Polygenic Inheritance Quantitative Characters