Presentation is loading. Please wait.

Presentation is loading. Please wait.

Mendelian Inheritance

Similar presentations

Presentation on theme: "Mendelian Inheritance"— Presentation transcript:

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


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 Square
TY 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 Square
db 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

Download ppt "Mendelian Inheritance"

Similar presentations

Ads by Google