1. Heredity
Ch. 13, 14

2. Traits
Physical attributes (hair color)

3. Genes Sections of DNA that code for a specific trait
AGCGTTTACT = red hair (phenotype)

4. Chromosomes
DNA wrapped around histones

5. Alleles
Different forms of a gene
R: red allele
r: gray allele

6. Genetics Review
Genotype: Rr
Phenotype: red hair

7. Charles Darwin Natural Selection
Favorable traits are passed on to offspring
Unfavorable traits mean death & no offspring!
But he couldn’t figure out how…

8. A few years later: 1860’s Gregor Mendel: Inheritance
How traits are passed on (parent  offspring)

9. Why study peas? Many varieties: Control reproduction: Short lifespan:
white flowering plant or purple flowering plant
Control reproduction:
cross-pollinate/hybrid or self-pollinate/purebred
Short lifespan:
Three generations in only three years
P-generation, F1-generation, F2-generation

10. Pea Traits
Collected thousands of pieces of data

11. Let’s do some science!

12. Mendel’s Experiment 1 Self pollinated pea plants to many generations
Purebred P-generation

13. Mendel’s Experiment 1 P gametes Resulting F1-generation Hybrid
Law of Dominance
Genotype:
Heterozygous alleles Pp

14. Mendel’s Experiment 1 F1 gametes Resulting F2-generation Phenotype:
3 purple: 1 white
Genotype:
1PP:2Pp:1pp

15. Law of Segregation
Discrete units of a trait segregate into separate gametes during gamete formation

16. Ex: Complete Dominance
In rabbits long ears are dominant to floppy ears. If a purebred long eared rabbit mates with a hybrid rabbit, what is the probability a bunny will be a hybrid?

17. Monohybrids are cool, but…
Observing two traits in one cross

18. Experiment 2 P-generation gametes: Resulting F1-generation? Purebred:
round RR yellow YY
green rr wrinkled yy
Resulting F1-generation?

19. Experiment 2 P-generation gametes: Resulting F1-generation
Purebred:
round RR yellow YY
green rr wrinkled yy
Resulting F1-generation
Hybrid
Round Rr and Yellow Yy
Resulting F2-generation?

20. Experiment 2 F1-generation gametes Resulting F2-generation
(RrYy X RrYy)
Resulting F2-generation
All pea styles

21. Law of Independent Assortment
The inheritance of one gene does not influence inheritance of another

22. Ex: Dihybrid Cross
In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s)
cross a purebred short tailed, white cat with a purebred brown, long tailed cat

23. Ex: Dihybrid Cross
In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s)
Parents: SSbb X ssBB
FOIL:

24. Ex: Dihybrid Cross
In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s)
F1: Hybrid for both traits
SsBb
F2 generation??????

25. Ex: Dihybrid Cross
In cats Brown hair (B) is dominant to white hair (b) AND short tail (S) is dominant to long tail (s)
F2 Generation
9 brown and short tail
3 white and short tail
3 brown and long tail
1 white and long tail

26. Complicated Genetics
Life is complex

27. Ex: Incomplete Dominance
F1 hybrids have an intermediate appearance
Ex: Snapdragons
red x white 

28. Ex: Incomplete Dominance
F1 hybrids have an intermediate appearance
Ex: Snapdragons
red x white  pink
Key
RR - red
RW - pink
WW - white

29. Ex: Codominance Both alleles are expressed dominantly Ex: Roan horses
Neither allele is recessive
Ex: Roan horses
red x white 

30. Ex: Codominance Both alleles are expressed dominantly Ex: Roan horses
Neither allele is recessive
Ex: Roan horses
red x white  Red and White
Key
RR - red
RW - roan
WW - white

31. Ex: Multiple Alleles More than two alleles are present for one trait
Ex: Blood Groups
A is dominant over O
B is dominant over O
A & B are codominant

32. Ex: Multiple Alleles More than two alleles are present for one trait
Ex: Blood Groups
A is dominant over O
B is dominant over O
A & B are codominant
Key
AA & AO: type A
BB & BO: type B
AB: type AB
OO: type O

33. Ex: Sex-linked Traits Traits that are associated with the X chromosome
Ex: Red-green colorblindness

34. Ex: Sex-linked Traits Traits that are associated with the X chromosome
Ex: Red-green colorblindness
Key:
XCXC: female normal
XCXc: female carrier
XcXc: female colorblind
XCY: male normal
XcY: male colorblind

35. Epistasis* Multiple genes affect one trait
Gene 1 codes for brown or black mice
Gene 2 codes for pigment in general

36. Pleiotropy* One gene affects multiple traits
Ex: Cats with blue eyes are deaf

37. Polygenic Inheritance*
A continuum of one trait is affected by multiple genes
Ex: human skin color
Three separate genes code for 7 shades of skin color

38. Visualizing Genetics

39. Pedigrees Show relationships within a family
Track traits or disease in a family

40. Example of Pedigree Charts
Dominant or Recessive?
Is this pedigree dominant or recessive?

41. Example of Pedigree Charts
Dominant or Recessive?
Is this pedigree dominant or recessive?

42. Trisomy 21 Occurs when an individual receives an extra 21st chromosome
Causes Down’s Syndrome

43. Trisomy 13 Occurs when an individual receives an extra 13th chromosome
Causes Patau Syndrome

44. Klinefelter’s Syndrome
Occurs when males receive an extra X chromosome
Causes men to be sterile

45. Jacob’s Syndrome Occurs when males receive an extra Y chromosome.
Causes men to become overly aggressive

46. Monosomy X Syndrome Occurs when females only receive one X chromosome
Causes Turners Syndrome