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Unformatted text preview: Sheet1 Page 1-Inheritance-Gregory Mendel-Alleles : different forms of a gene (the ones you get from mom/dad) Ex: S = round s = wrinkled Capitalization indicated dominancy, S is dominant, s is recessive With 2 genes: you have possibilities ss = recessive homozygous (wrinkled) Punnet SquareSs SSSSs sSsss Phenotype: what you see (a gene being expressed) Genotype: the genes you have (whether expressed or not) Incomplete dominance : heterozygote form blends characters together (not really blending) Segregation: in gamete formation, the 2 genes of a parent separate in Meiosis 1 so that each daughter cell (gamete) receives Generations: parent (P) Phenotypes v. genotypes How to determine if homozygous dominant (EE) v. heterozygous (Ee) ?to do this, cross with recessive homozygous (ee)-if it is homozygous (dominant(EE)), all genotypes will be heterozygous (Ee)-if it is heterozygous(Ee), half of the genotypes will be recessive homozygous (ee) Independent assortment : 2 different traits on different non-homologous chromosomes will segregate without regard to each o-phenotypic ratios if heterozygous for both traits. Parental Generation (P) Round Yellow Wrinkled Green SSYYxssyy F1 generationSsYy SYSysYsy F2 generation Sperms Eggs SYSysYsy SYSSYYSSYySsYYSsYy SySSYySSyySsYySsyy sYSsYYSsYyssYYssYy SySsYySSyySsYySsyy 9 are round yellow Blending h does not exist (black + white ? gray) isnht true SS h dominant homozygous (round), Ss = heterozygous (round) Sheet1 Page 2 3 are winkle yellow? these numbers are typical of 16 punnit square 3 round green 1 wrinkled green Incomplete dominance: blending of different forms of alleles ? differs from old idea of blending Ex type AB blood cells Multiple Alleles (more than 2 forms of a gene) Blood TypeGenotypeAntibodies made A[A]A or [A]OAnti B B[B]B or [B]OAnti A AB[A]BNeither anti A nor Anti B O[O]OBoth Anti A and Anti B Epitasis : One gene masks expression of any other genes affecting a trait Example: Hair color has a lot of genes that affect it, sometimes there is a gene that masks all other genes which is called epita ?In Labrador retrievers, the black gene is the epitasis (covers yellow etc. genes) There are several genes for one characteristic, an epitasis will mask all others Continuous variation : many genes & environment result in a gradient of a character Sex Chromosomes: Two types of sex chromosomes: X & Y--These determine sex of individual Females have XX (homozygous) males have XY (heterozygous)--In mammals, male determines sex of offspring (in bird, females determine sex of offspring) Because Y chromosome is much short than X, for some genes there is no counterpart on the Y. This is called a sex-linked characteristic because there is no counterpart on Y which allows an allele on X chromosome to be Carrier: female does not show that character but one of her x chromosomes has that allele....
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This note was uploaded on 12/11/2008 for the course BIO 213 taught by Professor Lee during the Spring '08 term at Cal Poly.
- Spring '08