1. how characteristics (traits) pass from parents to offspring
Genetics
The study of Heredity
how characteristics (traits) pass from parents to offspring

2. What does genetics have to do with DNA?
Genes stated clearly. 5 mins

3. Gregor Mendel
- A monk who studied peas in his garden and developed our basic understanding of heredity.

4. Allele Mendel’s term for Alternate forms of a trait.
Most traits have 2 alleles
Ex. Yellow or green pea

5. Blue eye or brown eye allele

6. Mendel said traits could be Dominant or recessive
Dominant – The trait that is stronger or masks the other trait
Recessive – The trait that is weaker or hidden in presence of dominant one

7. If there are both a dominant and recessive traits together, only the dominant one appears

8. Ex. Dominant gene
Black fur is usually dominant to white

9. Ex. Recessive genes Blue eyes and blond hair

10. Mendel’s Law of segregation
Offspring can only receive one allele or the other. They segregate from each other during meiosis
When gametes (sperm and egg) form, only one of the 2 possible genes for each trait will be in each gamete

11. Mendel’s Law of independent assortment
Alleles separate independently.
During meiosis, each homologous pair of chromosomes separate independently.
Different combinations possible

12. What Mendel did NOT know about?
Genes
DNA
Chromosomes
Meiosis
He still figured out how it worked with out knowing the details

13. Genes
A single unit of hereditary information (DNA) located on a chromosome

14. Locus (loci)
A gene’s specific location on a chromosome

15. Pure Strain Called True Breeding
When crossed with in strain, all the offspring have the same trait
The genes are all the same
Often called “Pure bred”

16. Hybrid When an organism has both forms of the gene (both alleles)
Ex. Heterozygous pepper has one gene for yellow and one gene for red

17. G g Genotype The genes an organism carries
Ex: Gg = a green (G) and yellow (g) gene G g

18. Phenotype How the genes are expressed (what it looks like)
Ex: Aa peas have both green and yellow genes but the phenotype is yellow because yellow is dominant

19. G Homozygous Dominant Two Dominant Genes Genotype = GG
Phenotype = Green GG G G

20. g Gg G Heterozygous 1 Dominant gene and 1 recessive gene Genotype = Gg
Phenotype = Green g Gg G

21. gg g g Homozygous Recessive Two recessive Genes Genotype = gg
Phenotype = Yellow gg g g

22. Monohybrid cross Look at one single trait Cross RR X rr  get all Rr
Cross Rr X Rr  get 1RR + 2Rr + 1rr
3:1 ratio of
dominant phenotype

23. Generations of a cross P1 Generation – The original parents
F1 Generation – The first offspring
(Children)
F2 Generation – The offspring from the F1 gen. (grandchildren)

24. P1 = BB (brown) X bb (blond)
F1 Offspring:
BB =
Bb = B b

25. P1 = BB (brown) X bb (blond)
F1 Offspring:
BB =
Bb = B b Bb

26. P1 = BB (brown) X bb (blond)
F1 Offspring:
BB =
Bb = B b Bb

27. P1 = BB (brown) X bb (blond)
F1 Offspring:
BB =
Bb = B b Bb

28. P1 = BB (brown) X bb (blond)
F1 Offspring:
BB =
Bb = B b Bb

29. P1 = BB (brown) X bb (blond)
F1 Offspring:
BB =
0% Brown
Bb =
100% Brown
bb =
0% Blond B b Bb

30. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB =
Bb =
bb = B b

31. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB =
Bb =
bb = B b BB

32. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB =
Bb =
bb = B b BB Bb

33. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB =
Bb =
bb = B b BB Bb

34. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB =
Bb =
bb = B b BB Bb bb

35. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB = 25% Brown
Bb =
bb = B b BB Bb bb

36. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB = 25% Brown
Bb = 50% Brown
bb = B b BB Bb bb

37. Cross two hybrids Bb X Bb from F1 generation
F2 Offspring:
BB = 25% Brown
Bb = 50% Brown
bb = 25% blond B b BB Bb bb

38. Dihybrid cross
Look at 2 traits at same time when crossing 2 hybrids

39. DiHybrid example

40. 9 : 3 : 3 : 1 ratio 9 Dom / Dom Tall/Red 3 Dom / res short/Red
3 res / Dom Tall/yellow
1 res / res short/yellow

41. Other inheritance patterns

42. Incomplete dominance
When a the phenotype is a mixture of the two alleles. Causing Blending!
Ex: Red and White make Pink

43. Ex. Incomplete dominance snap dragons
Cr X Cw

44. Co- dominance - When both traits show up. Both dominant
Blood type is Co Dominant
Ex: AB blood type has both A and B proteins

45. Ex. Co dominance in chickens
Have both color feathers

46. Ex. Codominance in cattle
Red and white make roan

47. Multiple alleles More than 2 alleles Blood type has 3 alleles
IA – Type A
IB – Type B
i – Type O

48. Blood types
AB - Universal receiver
O - Universal donor

49. Blood types in America

50. Polygenic inheritance traits
When there is more than one gene for a trait. Ex. Eye color, height

51. Epistasis When the effects of one gene are modified by another gene.
Ex. Albino gene - overrides other genes that determine color

52. Labrador retrievers are polygenic
           
           
Black (B) is dominant to chocolate (b) BUT Yellow is recessive epistatic ee changes all yellow
Phenotype- Possible
Genotypes
BBEE BbEE BBEe BbEe
bbEE bbEe
BBee Bbee bbee

53. X - linked traits When a trait is carried on the X chromosome
Females (XX) need both genes
Males (XY)
need only one gene to have trait