Genetics Patterns of Inheritance. Biology 20

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1 Genetics Patterns of Inheritance Biology 20

2 Genetics Study of heredity Aristotle Pangenes Von Leewenhoek Homounculus de Graff ovarian follicle is a miniature person

3 Blended Theory Genetic material mixes (intermediate btn parents) Individuals in a pop. should reach a uniform appearance w/ time

4 Gregor Mendel ( ) 1. Particulate Theory Gene idea 2. Character 3. Trait 1. Parents pass on discrete inheritable units of info to offspring 2. Detectable inheritable feature of an organism. Ex. seed color, hair color, seed shape, plant height 3. Each variant of a character Ex. seed color (green/yellow), hair color (brown/blonde) seed shape (round/wrinkled)

5 Mendel

7 Genetics Terms Alleles Dominant Recessive Genotype Homozygous dominant: Homozygous recessive: Heterozygous: Phenotype Alternative versions of gene Inherited feature Genetic make-up Arrangement of alleles 2 identical alleles (TT) 2 identical alleles (tt) 2 different alleles (Tt) Physical appearance

8 True breeding Produce offspring with the same trait as parents

9 True breeding Homozygous tall TT x TT Homozygous short tt x tt T T t t T TT TT t tt tt T TT TT t tt tt All Tall All Short

10 P Generation Cross Tall x short TT x tt T T F 1 Genotype: All Tt t Tt Tt t Tt Tt F 1 Phenotype: All tall

11 Monohybrid Cross Principle of Segregation 1. the pair of genes for each character: segregate (separates) during gamete production 2. fusion of gametes at fertilization: pairs genes once again

12 Principle of Segregation

13 Two people that are heterozygous for brown eyes mate. What are the possible eye colors of their offspring? B = brown b = blue P - Genotype: Bb x Bb B b F 1 Genotype: B BB Bb 1 BB:2 Bb:1 bb b Bb bb F 1 Phenotype: 3 Brown:1 blue

14 Dihybrid Crosses Mendel's Principle of Independent Assortment: each allele pair segregates (separates) independently of other gene pairs during gamete formation formula: 2 n where n = # of heterozygous pairs => to produce the unique gametes

15 How many unique gametes will be produced for the following genotypes? a) RrYy b) AaBbccDD c) AAbb What are the unique gametes? a) 4 b) 4 c) 1 RY, Ry, ry, ry ABcD, AbcD, abcd, abcd Ab d) AABBccDdeeFFggHHiiJJKKLLmmnnooPPqqRRssTT d) 2 What are they? ABcDeFgHiJKLmnoPqRsT ABcdeFgHiJKLmnoPqRsT

20 Test Cross Identify genotype of dominant individual Cross with known genotype (recessive p P Pp P Pp P = Purple flowers p = white flowers p P Pp p pp PP or Pp x pp

21 Figure 9.5B_1 Test Cross Blind Phenotypes Genotypes Black coat, normal vision B_N_ Black coat, blind (PRA) B_nn Blind Phenotypes Genotypes Chocolate coat, normal vision bbn_ Chocolate coat, blind (PRA) bbnn

22 Rules of Figure 9.7 F 1 genotypes Bb female Bb male Probability Formation of eggs Formation of sperm B 1 2 ( ) 1 2 Sperm b 1 2 B B B B b F 2 genotypes Eggs b b B b b

23 Incomplete Dominance

24 Figure 9.11B Incomplete Dominance A mom has high blood cholesterol whereas her husband is normal. LDL receptor HH Homozygous for ability to make LDL receptors LDL What s the probability that their child will have high blood cholesterol like their mother? Genotypes Hh Heterozygous Phenotypes hh Homozygous for inability to make LDL receptors Cell Normal Mild disease Severe disease

25 Blood Groups Co-dominance Where both alleles are expressed AB blood Multiple Alleles More than 2 alleles determine genotypes 3 alleles I A, I B and I O or i

26 Figure 9.12_1 Blood Group (Phenotype) Genotypes Carbohydrates Present on Red Blood Cells A I A I A or I A i Carbohydrate A B I B I B or I B i Carbohydrate B Carbohydrate A AB I A I B and Carbohydrate B O ii Neither

27 Figure 9.12 Blood Group (Phenotype) Genotypes Carbohydrates Present on Red Blood Cells Antibodies Present in Blood Reaction When Blood from Groups Below Is Mixed with Antibodies from Groups at Left O A B AB A I A I A or I A i Carbohydrate A Anti-B B I B I B or I B i Carbohydrate B Anti-A AB I A I B Carbohydrate A and Carbohydrate B None O ii Neither Anti-A Anti-B No reaction Clumping reaction

28 Blood Information Universal donor Universal recipient Antigens cell identifier (CHO) Antibodies defense (protein) Rh factor (Rhesus factor) Rh (+) or Rh (-) RhoGAM

29 One gene multiple affects Pleiotropy

Epistasis One gene affects (controls) another gene s expression The eye color genes code for the production of a yellow-brown pigment First Iris Layer Pigment AA = Produce lots of pigment Aa =

30 Epistasis One gene affects (controls) another gene s expression The eye color genes code for the production of a yellow-brown pigment First Iris Layer Pigment AA = Produce lots of pigment Aa = Produce some pigment aa = Do not produce pigment Second Iris Layer Pigment BB = Produce lots of pigment Bb = Produce some pigment bb = Do not produce pigment Yellow overlay gene When combined with the basic pigment gene alters: Light brown to hazel Light blue to green

31 Epistasis Fur pigment E = dark pigment ee = no pigment Darkness & distribution of pigment B = dark b = light eebb eeb_ E_bb E_B_

32 Epistasis

33 Polygenic Inheritance 2+ genes affects phenotype Examples: Skin color Height Hair pigmentation

34 Environment affects phenotype Phenocopy

35 Recessively Inherited Disorders Heterozygous normal no disorder carrier Albinism Chromosome 11 1/22,000

36 Recessively Inherited Disorders Tay Sachs Disease Chromosome 15 Lipid accumulation in brain Occurs: In utero death by 5 yrs Juvenile (~4 yrs) death by 15 Adult (~30 yrs) milder 1/3500 central European Jews

37 Recessively Inherited Disorders Cystic Fibrosis Chromosome 7 Accumulation of Cl - Mucus build-up in lungs & liver 1/1,800 Caucasians 1/28 Caucasians unknown carriers

38 Recessively Inherited Disorders Phenylketonuria (PKU) Phenylalanine Mental retardation 1/10,000 US & Europe

39 Dominantly Inherited Disorders Achondroplasia (dwarfism) Chromosome 7 Growth hormone deficient 1/25,000

40 Dominantly Inherited Disorders Phenylthiocarbamide (PTC) Polydactyly Extra digits

41 Dominantly Inherited Disorders Huntington s Disease Chromosome 4 Begins in middle age Nervous degeneration

43 Linked Genes Inherited together Do not assort independently

44 Sex-linked Genes X-linked most X-linked genes have no homologous loci on the Y chromosome genes located on the sex chromosomes X two sex chromosomes X & Y females XX, males XY fathers pass X-linked alleles to only and all of their daughters Normal X A X A X A X a X A Y Sex-linked disorder X a X a X a Y

46 Males have more sex-linked disorders than females. WHY?

47 Sex-linked Cross

48 Sex-linked Cross

49 A man with normal vision marries a woman who has normal vision but whose father was colorblind. 1. What is the genotype for the man & woman? 2. What % of their children will have normal vision? 3. What % of their sons will have normal vision? 4. What % of their daughters will have normal vision? 5. Will they have any colorblind children? If so, whom? 1. X A Y and X A X a. X A X a X A X A X A X A X a Y X A Y X a Y

50 A man with normal vision marries a woman who has normal vision but whose father was colorblind. 1. What is the genotype for the man & woman? 2. What % of their children will have normal vision? 3. What % of their sons will have normal vision? 4. What % of their daughters will have normal vision? 5. Will they have any colorblind children? If so, whom? 1. X A Y and X A X a % 3. 50% % 5. Yes, males.

51 Red-green colorblindness

52 Hemophilia

53 Sex Influenced Trait Pattern Baldness Male Female BB Normal normal Bb Bald normal bb Bald thin BbXY BbXX Balding male Normal female

54 Carrier recognition: Tests for heterozygotous carriers for: Tay-Sachs allele, cystic fibrosis & sickle-cell Enables people to: Make informed decisions about having children Could also be abused: Ethical dilemmas about social implications of technology

55 Fetal Testing Alpha fetoprotein (AFP) Amniocentesis Protein levels associated with Downs

56 Fetal Testing Alpha fetoprotein (AFP) Amniocentesis Choronic villi sampling

57 Figure 9.10A Amniocentesis Ultrasound transducer Amniotic fluid extracted Ultrasound transducer Chorionic Villus Sampling (CVS) Tissue extracted from the chorionic villi Fetus Placenta Uterus Cervix Fetus Placenta Chorionic villi Cervix Centrifugation Uterus Amniotic fluid Fetal cells Cultured cells Several hours Several weeks Biochemical and genetics tests Fetal cells Several hours Several weeks Several hours Karyotyping

58 Fetal Testing Alpha fetoprotein (AFP) Amniocentesis Choronic villi sampling Ultrasound

Mendel & Inheritance. SC.912.L.16.1 Use Mendel s laws of segregation and independent assortment to analyze patterns of inheritance.

Mendel & Inheritance. SC.912.L.16.1 Use Mendel s laws of segregation and independent assortment to analyze patterns of inheritance. Mendel & Inheritance SC.912.L.16.1 Use Mendel s laws of segregation and independent assortment Mendel s Law of Segregation: gene pairs separate when gametes (sex cells) are formed; each gamete as only