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bio notes - -Inheritance Blending does not exist (black +...

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-Inheritance Blending – does not exist (black + white gray) isn’t true -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 – dominant homozygous (round), Ss = heterozygous (round) ss = recessive homozygous (wrinkled) Punnet Square S s S SS Ss s Ss ss 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 only one of the genes. Generations: parent (P); first filial (F1); second filial (F2) 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 other. (SsYy) -phenotypic ratios if heterozygous for both traits.
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Parental Generation (P) Round Yellow Wrinkled Green SSYY x ssyy F1 generation SsYy SY Sy sY sy F2 generation Sperms Eggs SY Sy sY sy SY SSYY SSYy SsYY SsYy Sy SSYy SSyy SsYy Ssyy sY SsYY SsYy ssYY ssYy Sy SsYy SSyy SsYy Ssyy 9 are round yellow 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 Co dominance – both alleles exposed in heterozygote Ex type AB blood cells -There is Type A, B, O etc. and AB (which isn’t A or B) Multiple Alleles (more than 2 forms of a gene) Blood Type Genotype Antibodies made A [A]A or [A]O Anti B B [B]B or [B]O Anti A AB [A]B Neither anti A nor Anti B O [O]O Both 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 epitasis 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 Pleiotropy – expression of an allele can affect expression of an unrelated phenotype --Ex: a gene that affects shape of hemoglobin –sickle cell anemia (gene is for hemoglobin but affects shape of cell) Continuous variation : many genes & environment result in a gradient of a character
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Sex Chromosomes: Karyotyping: distinguishing among the different chromosomes –autosomes v. sex chromosomes Two types of sex chromosomes: X & Y --These determine sex of individual Females have XX (homozygous) males have XY (heterozygous)
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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.

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bio notes - -Inheritance Blending does not exist (black +...

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