Genetics. The study of heredity. Father of Genetics: Gregor Mendel (mid 1800 s) Developed set of laws that explain how heredity works

Transcription

1 Genetics The study of heredity Father of Genetics: Gregor Mendel (mid 1800 s) Developed set of laws that explain how heredity works

2 Father of Genetics: Gregor Mendel original pea plant (input) offspring (output) What happened here??

3 Mendel s subjects: pea plants

4

5 How To Read A Punnett Square What is the P Generation? What is the F1 Generation? What must parents undergo to produce haploid gametes? What is phenotype? What is genotype? Does genotype largely determine phenotype?

6 Monohybrid Crosses: parents differ by one characteristic Was the heritable factor of green peas lost? Watch Amoeba Sisters Monohybrids and the Punnett Square Guinea Pigs

7 Mendel s Conclusions 1. How many forms of genes (alleles) does each individual have for each trait? 2. How does an individual get these genes (alleles)? 3. How many alleles for each trait does each gamete (sperm or egg) contain?

8 Mendel s Conclusions 4. What must the alleles do in order to only have one allele for each trait in each gamete? 5. How many alleles for each trait are present in the embryo when fertilization occurs (the union of sperm and egg)?

9 Law of Separation Pairs of alleles separate during egg & sperm formation (meiosis) & fusion of egg & sperm at fertilization creates allele pairs again.

10 8. What do we call an allele when it masks the expression of the other allele? Example? 9. What do we call an allele whose trait is being masked? Example?

11 Alleles on Homologous Chromosomes 1 chromosome comes from mother & other from father Homologous chromosomes may have either same or different alleles at a location.

12 Alleles on Homologous Chromosomes Homozygous? When organism has a pair of identical alleles for a gene ( or ) (homozygous dominant or homozygous recessive)

13 Alleles on Homologous Chromosomes Heterozygous? When organism has two different alleles for a gene ( )

14 Pairs of alleles separate during egg & sperm formation (meiosis) & fusion of egg & sperm at fertilization creates allele pairs again = Law of Segregation

15 Phenotypes & genotypes of parents? Male Female Eggs & sperm of parents? Sperm Eggs Phenotypes & genotypes of offspring? Phenotypic ratio? Genotypic ratio? F1 Generation

16 Phenotypes & genotypes of parents? Male Female Eggs & sperm of parents? Sperm Eggs Phenotypes & genotypes of offspring? T t Tt Tall t Tt Tall Phenotypic ratio? Genotypic ratio? T Tt Tall Tt Tall F1 Generation

17 Phenotypes & genotypes of parents? F 1 Generation X Eggs & sperm of parents? Phenotypes & genotypes of offspring? Phenotypic ratio? Genotypic ratio?

18 Practice this one on your own PP pp 1. Phenotypes & genotypes of parents? 2. Eggs & sperm of parents? 3. Phenotypes & genotypes of offspring? 3. Phenotypic & genotypic ratios?

19 Is this article true or false? Why? Recessive alleles don t get wiped out. They get passed on and retain potential to have effect but must be paired with another recessive allele.

20

21 Fraternal twins whose parents are both mixed race (blackwhite unions). One twin inherited alleles passed on from her black grandparents while other inherited alleles passed on from white grandparents.

22

23 Dihybrid Crosses: parents differ by two characteristics smooth & yellow wrinkled & green Watch Amoeba Sisters Two-Trait and Dihybrid Crosses smooth & yellow

24 Mendel s Conclusions 1. Do all possible combinations of traits occur in the gametes? 2. Does each pair of traits separate independently of the other pairs?

25

26 Law of Independent Assortment Each pair of alleles separates independently of the other pairs during gamete formation. Inheritance of one characteristic has no effect on inheritance of another.

27 Tall & green pods Short & yellow pods male female F1 generation Phenotypic ratio? Genotypic ratio?

28 Tall & green pods Short & yellow pods male female tg tg tg tg TG TtGg TtGg TtGg TtGg F1 generation TG TtGg TtGg TtGg TtGg Phenotypic ratio? TG TtGg TtGg TtGg TtGg Genotypic ratio? TG TtGg TtGg TtGg TtGg

29 Tall & green pods X Phenotypic ratio?

30 Practice this one on your own

31 Mendel s Principles & Human Inheritance Mendel s principles apply to the inheritance of some human traits

32 Human Disorders Controlled by a Single Gene Genes involved in these disorders are located on autosomes = chromosomes other than sex chromosomes X & Y

33 Autosomal Recessive Disorders Person w/ a single properly functioning allele will not suffer from disorder; recessive Parents are heterozygous & are carriers of recessive allele for disorder but are phenotypically normal Can they produce a child that exhibits the condition? What is the probability of this happening?

34 Sickle-Cell Anemia

35 Autosomal Recessive Disorders

36 Autosomal Dominant Disorders A single faulty allele can cause a disorder even when a properly functioning allele exists. Parent need only pass on a single allele for offspring to suffer from condition. Usually individuals w/ disorder are heterozygous (Dd) for the disorder.

37 Autosomal Dominant Disorders Ex. Huntington disease Probability that child will exhibit condition?

38 Autosomal Dominant Disorders Ex. Huntington disease Probability that child will exhibit condition?

39 Autosomal Dominant Disorders

40 Pedigrees are used to determine inheritance of characteristics that follow Mendel s principles in humans.? d d d? Is deafness a dominant or recessive disorder?? Watch Amoeba Sisters Pedigree

41 You can tell who are heterozygous carriers of the recessive condition. How so?? d d d? Is deafness a dominant or recessive disorder??

42 1. Fill in known genotypes first. 2. Use that info to determine the unknown genotypes.? d d d? Is deafness a dominant or recessive disorder??

43 Incomplete Dominance Neither allele is dominant Heterozygote phenotype is intermediate between either of the homozygous phenotypes One red allele produces only enough pigment to yield pink color Watch Amoeba Sisters Incomplete Dominance, Codominance, Polygenic Traits, and Epistasis!

44 Multiple Alleles When more than 2 possible alleles exist in a population. Each individual carries, at most, 2 different alleles for a particular gene, however, more than 2 possible alleles exist in a population. Watch Amoeba Sisters Multiple Alleles (ABO Blood Types) and Punnett Square

45 Multiple Alleles Human blood types: 3 alleles for blood type A, B & O which can produce 4 phenotypes (A, B, O or AB)

46 Multiple Alleles Human blood types: 3 alleles for blood type A, B & O which can produce 4 phenotypes (A, B, O or AB)

47 Codominance Both alleles are dominant so both are displayed What alleles are both dominant? Who do we receive these alleles from?

48 Polygenic Inheritance Inheritance determined by interaction of multiple genes, with each gene having additive effect on trait Height, weight, eye color, skin color are controlled by several genes working together

49 Sex Determination Who contributes what?

50 Sex linked genes any gene located on a sex chromosome Watch Amoeba Sisters Punnett Squares and Sex- Linked Traits

51 Eye color in fruit flies Is white eye color dominant or recessive? Is the eye color allele on the X or Y chromosome? X-linked trait

52 Eye color in fruit flies What alleles does this female carry? Will she be red or white eyed? What allele does the male carry? Will he be red or white eyed? Can white eyed males be produced from this cross? How would a female get white eyes?

53 How would a female get white eyes? Eye color in fruit flies

54 Red-Green Color Blindness

55 Is color blindness on the X or Y chromosome? Color blindness Is color blindness a dominant or recessive? Which child will be color blind?

56 Color blindness How would a daughter be color blind??

57 Sex (X) Linked Disorders

58 Genes & Environment

59 Effects of genes vary according to environment in which genes are expressed Organism s genotype & environment interact to produce organism s phenotype

60 Effects of genes vary according to environment in which genes are expressed Organism s genotype & environment interact to produce organism s phenotype

61 Effects of genes vary according to environment in which genes are expressed Organism s genotype & environment interact to produce organism s phenotype

62 Epigenetics Our lifestyles and environment can change the way our genes are expressed, leading even identical twins to become distinct as they age.