1. Mendelian Inheritance
BIO 2215
Oklahoma City Community College
Dennis Anderson

2. Gregor Mendel Father of Genetics 1823-1884 Monk in Austria
Experimented with garden peas

3. Tall
Short
Tall

4. Mendel’s Hypotheses Each parent has two factors (alleles)
Each parent gives one of those factors to the offspring
Tall has TT
Short has tt
Tall is dominant
Short is recessive

5. TT tt Tt t T

6. TT TT TT T T

7. tt tt tt t t

8. Law of Segregation Alleles separate during gamete production
Gametes have one allele for each trait
During fertilization gametes combine at random to form individuals of the next generation

9. Discovery of Chromosomes in 1900 Confirmed Law of Segregation
Chromosomes are in pairs
Each chromosome has one of the allele pair

10. Meiosis Metaphase Chromosomes line up in a double row. T T t t
Assume a T allele on each red chromatid and a t allele on each blue chromatid

11. Chromosomes separate Each each daughter cell gets doubled chromosomes

12. Doubled Chromosomes Separate in Second Meiotic Division

13. Each gamete will have a T allele or a t allele

14. Allele Member of a paired gene Represented by a single letter
One allele comes from each parent
Represented by a single letter

15. Dominant & Recessive Alleles
Dominant alleles are expressed
Recessive alleles are not expressed in the presence of a dominant allele
Recessive alleles are only expressed if both recessive alleles are present

16. Gene A unit of heredity that controls the development of one trait
Made of DNA
Most genes are composed of two alleles

17. Homozygous
Both alleles alike
AA or aa

18. Heterozygous
Alleles are different Aa

19. Genotype Genetic make up Represented by alleles
TT & Tt are genotypes for tall pea plants

20. Phenotype A trait Genotype determines the phenotype
Tall is a phenotype

21. Homologous Chromosomes
Chromosomes of the same pair
Each homologue will have one allele for a paired gene
Homologous chromosomes pair up during meiosis
Only one of each homologue will be in each gamete

22. Sickle Cell Anemia RBCs sickle shaped Anemia Pain Stroke Leg ulcers
Jaundice
Gall stones
Spleen, kidney & lungs

23. Sickle Cell Anemia Recessive allele s, codes for hemoglobin S
Long rod-like molecules
Stretches RBC into sickle shape
Homozygous recessive ss, have sickle cell anemia
Heterozygous Ss, are carriers

24. Albinism
Lack of pigment
Skin
Hair
Eyes

25. a A Enzyme Amino Acids Melanin Pigment AA = Normal pigmentation
aa = Albino

26. PKU Disease
Phenylalanine excess
Mental retardation if untreated

27. p P
Enzyme
Phenylalanine
Tyrosine
PP = Normal
Pp = Normal
pp = PKU

28. Monohybrid Cross or One Trait
A man & woman are both carriers (heterozygous) for albinism. What is the chance their children will inherit albinism?

29. AA = Normal pigmentation
Aa = Normal pigmentation (carrier)
aa = Albino
Man = Aa
Woman = Aa A A a a

30. A a A Aa AA a Aa aa

31. AA Aa aa Genotypes Phenotypes Probability 1 AA, 2Aa, 1aa 3 Normal
1 Abino
Probability
25% for albinism

32. A man & woman are both carriers (heterozygous) for PKU disease
A man & woman are both carriers (heterozygous) for PKU disease. What is the chance their children will inherit PKU disease?

33. PP = Normal
Pp = Normal (carrier)
pp = PKU disease P p PP Pp pp P p

34. PP Pp pp Genotypes Phenotypes Probability 1 PP, 2Pp, 1pp 3 Normal
1 PKU disease
Probability
25% for PKU disease

35. A man with sickle cell anemia marries a woman who is a carrier
A man with sickle cell anemia marries a woman who is a carrier. What is the chance their children will inherit sickle cell anemia?

36. SS = Normal
Ss = Normal (carrier)
ss = Sickle Cell S s s Ss ss s

37. Genotypes ss Ss Phenotypes Probability 2 Ss, 2ss 2 Normal (carriers)
2 Sickle cell
Probability
50% for Sickle cell

38. Dwarfism DD = Dwarfism Dd = Dwarfism dd = Normal height Dwarfism = D
Dwarf Band

39. A man with heterozygous dwarfism marries a woman who has normal height
A man with heterozygous dwarfism marries a woman who has normal height. What is the chance their children will inherit dwarfism? Dwarfism is dominant.

40. DD = Dwarf
Dd = Dwarf
dd = Normal d d D Dd dd d

41. Genotypes Dd Phenotypes dd Probability 2 Dd, 2dd 2 Normal 2 Dwarfs
50% for Dwarfism

42. Law of Independent Assortment
The inheritance of one gene does not influence the inheritance of another gene if they are on separate chromosomes.
The gene for albinism does not affect the gene for dwarfism

43. Dihybrid Cross or Two Traits
A heterozygous tall plant that is also heterozygous for yellow seeds is crossed with another plant with the same genotype
Tall and yellow seeds are dominant to short and green seeds.

44. What gametes can each parent produce?
Tall Yellow
Tall Yellow
TtYy
TtYy TY TY Ty tY ty Ty tY ty

45. Match gametes on a Punnent SquareTY Ty tY ty
TtYy
TTYY
TTYy
TtYY
TTyy
Ttyy
ttYY
ttYy
ttyy
9 Tall-Yellow TY Ty tY ty
3 Tall-Green
3 Short-Yellow
1 Short-Green

46. A man with blue eyes and normal height marries a woman with heterozygous brown eyes and heterozygous dwarfism. What are the possible phenotypes of their children? Dwarfism & brown eyes are dominant.

47. What gametes can each parent produce?
Normal height-Blue
Dwarf-Brown
ddbb
DdBb db DB Db dB db

48. Match gametes on Punnent Squaredb
DdBb
Ddbb
ddBb
ddbb
Dwarf-Brown eyes
Dwarf-blue eyes
Normal height-Brown eyes
Normal height-Blue eyes DB Db dB db

49. The End