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

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Presentation on theme: "1 Mendelian Inheritance BIO 2215 Oklahoma City Community College Dennis Anderson."— Presentation transcript:

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

2 2 Gregor Mendel Father of Genetics Monk in Austria Experimented with garden peas

3 3 Short Tall

4 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 5 TTtt T t Tt

6 6 TT T T

7 7 tt t t

8 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 9 Discovery of Chromosomes in 1900 Confirmed Law of Segregation Chromosomes are in pairs Each chromosome has one of the allele pair

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

11 11 Chromosomes separate Each each daughter cell gets doubled chromosomes TT tt

12 12 Doubled Chromosomes Separate in Second Meiotic Division TT tt

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

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

15 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 16 Gene A unit of heredity that controls the development of one trait Made of DNA Most genes are composed of two alleles

17 17 Homozygous Both alleles alike AA or aa

18 18 Heterozygous Alleles are different Aa

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

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

21 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 22 Sickle Cell Anemia RBCs sickle shaped Anemia Pain Stroke Leg ulcers Jaundice Gall stones Spleen, kidney & lungs

23 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 24 Albinism Lack of pigment –Skin –Hair –Eyes

25 25 Amino AcidsMelanin Pigment Enzyme A a AA = Normal pigmentation Aa = Normal pigmentation aa = Albino

26 26 PKU Disease Phenylalanine excess Mental retardation if untreated

27 27 PhenylalanineTyrosine Enzyme P p PP = Normal Pp = Normal pp = PKU

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

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

30 30 A a a A AA Aa aa

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

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

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

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

35 35 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 36 s s s Ss ss S SS = Normal Ss = Normal (carrier) ss = Sickle Cell

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

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

39 39 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 40 d d D Dd dd Dd dd d DD = Dwarf Dd = Dwarf dd = Normal

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

42 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 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 44 Tall Yellow TtYy TY What gametes can each parent produce? Ty tY ty TtYy TY Ty tY ty Tall Yellow

45 45 9 Tall-Yellow Match gametes on a Punnent Square TY Ty tY ty TYTytYty TtYy TTYYTTYyTtYY TTYyTTyyTtyy TtYYTtYyttYYttYy TtYyTtyyttYyttyy 3 Tall-Green 3 Short-Yellow 1 Short-Green

46 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 47 Normal height-Blue ddbb db What gametes can each parent produce? DdBb DB Db dB db Dwarf-Brown

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

49 49 The End


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