Biology 20 Lecture Genetics Page 1 of 6 Biololgy 20 GENETICS Genetics: Genetics History: Aristotle: pangenes Anton von Leewenhoek: homunculus Regnier de Graff: Blended Theory: Mendel (1822-1884): Particulate theory: Gene idea: Character: Trait: Terms: Alleles: Dominate alleles: Recessive alleles: Genotype: Homozygous dominant: Homozygous recessive: Heterozygous: Phenotype: Punnet square: What determines the phenotype? The arrangement of the alleles in the genotype determines. True breeding: Homozygous tall: Homozygous short: TT x TT tt x tt Phenotype? Phenotype? Cross of the homozygous plants (P Generation):Biology 20 Lecture Genetics Page 2 of 6 Tall (TT) x Short (tt) => Offspring are the F1 (1st filial) Generation Genotypes: Phenotypes: Breeding the F1 Generation: Tall (Tt) x Tall (Tt) pea plants => Offspring are the F2 Generation Genotypes: Phenotypes: Genotypic ratio: Phenotypic ratio: Monohybrid cross: the cross which tracks single character of inheritance Mendel’s Principle of Segregation: a) the pair of genes for each character: b) fusion of gametes at fertilization: How does the principle of segregation relate to meiosis? (p. 144; Fig. 8.17A) Monohybrid cross: Two people that are heterozygous for brown eyes mate. What are the possible eye colors of their offspring? Note: B = brown b = blue Dihybrid cross: Mendel's Principle of Independent Assortment: a) b) formula: 2n where n = # of heterozygous pairs How many unique gametes will be produced for the following genotypes? a) RrYy gametes b) AaBbccDD gametes c) AAbb gametes Mendel used pea characteristics => Seed color: Yellow (Y) - green (y) Seed shape: Round (R) - wrinkled (r)Biology 20 Lecture Genetics Page 3 of 6 F1 Generation cross: RrYy x RrYy (both heterozygous round and yellow seeds) Phenotypic ratio: Test cross: Ex. Purple flower (P) White flower (p) PP or Pp x pp Complete dominance: Incomplete dominance: F1 hybrids: Ex. Snapdragons Hypercholesterolemia RR = red HH = normal (make LDL receptors) rr = white hh = severe disease (can not make LDL receptors) Rr = pink Hh = mild disease ( makes some LDL receptors) Codominance: Multiple alleles:Biology 20 Lecture Genetics Page 4 of 6 Ex. A, B, O => three alleles =>IA, IB, i Blood type Possible Genotypes Antigens on RBC Antibodies in serum A IAIA IAIi A anti-B B IBIB IBIi B anti-A AB IAIB AB --- O ii --- anti-A anti-B Type O: Type AB: Foreign antigens cause the body to produce antibodies. Antibodies: Antigen: Rh factors: Rh (+) Rh (-) RhoGAM: Pleiotrophy: EX. Tigers & Siamese cats: Epistasis: Ex. P = purple p = white C = color c = no color ppcc = white PpCc = Purple PPcc = white Polygenic inheritance Phenocopy Recessively Inherited Disorders: If heterozygous: Types: Albinism: Cystic fibrosis: Tay-Sachs disease:Biology 20 Lecture Genetics Page 5 of 6 Sickle-cell anemia (1 in 400 African-Americans born in US) Consanguinity: Dominantly Inherited Disorders: Types: achondroplaisa (dwarfism): Huntington’s disease: Polydactyly: Linked genes: Sex-linked genes: Genes located: Fathers pass X-linked alleles to only and all of their? For example: A = normal gene; a = gene associated with a disorder Genotype Phenotype Genotype Phenotype XAXA normal female XAY normal male XAXa normal female (carrier) XaY sex-linked disorder XaXa sex-linked disorder Males have more sex-linked disorders than females. WHY? A man with normal vision marries a woman who has normal vision but whose father was colorblind. 1) What are the genotypes of the man and woman? 2) What percentage of their children will have normal vision? 3) What percentage of their sons will have normal vision? 4) What percentage of their daughters will have normal vision? 5) Will they have any colorblind children? If so, whom? Sex Influenced Traits:Biology 20 Lecture Genetics Page 6 of 6 Pattern-baldness: Genotype Men Women BB normal normal Bb bald normal bb bald thin 1) BbXY Æ what’s the phenotype? 2) BbXX Æ what’s the phenotype? Technology is providing new tolls for genetic testing and counseling: Carrier recognition: Tests for heterozygous carriers for: Enables people to: Could also be abused: Fetal testing: If a couple learns that they are both carriers for a genetic disease, can decide to have a child can determine if the fetus has the disease. Alpha fetoprotein (AFP): Amniocentesis: Chorionic villi sampling (CVS): Ultrasound: Fetoscopy: Newborn screening = to detect genetic disorders such as phenylketonuria (PKU) - PKU is recessively inherited and occurs in about 1 in 15,000 births in the