Discussion Section(kathleen) - handout 4

Discussion Section(kathleen) - handout 4 - BICD100Genetics...

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BICD 100 – Genetics TA: Kathleen Section Handout #4 (Week 6)                Office Hours:  F 9-10am,  CLICS study tables, first floor Summary of lecture 8, 9, 10 Alleles  are variants of the same gene, such as blood type, tongue-curling, wrinkled/round peas, etc. Locus : the specific location of a gene on the chromosome Test cross : crossing the unknown genotype with a  homozygous recessive  and check the progeny Two traits will separate independently if and only if the genes are on different chromosomes  OR  the two  genes are so far apart from each other on the same chromosome that crossing over is very likely Incomplete dominance : the “ blending ” of two phenotypes, creating a new phenotype that is intermediate of  the two original phenotypes (Curly hair + straight hair = wavy hair) Codominance : two phenotypes are  expressed together , but no new phenotypes are created (In ABO blood  system, for AB blood, both A and B glycoprotein antigens are expressed on the red blood cell.) Methods of determining probability – just know one method well! o Branch method      – crossing each trait individually to find out the final probabilities Rr x Rr Yy x Yy RrYy x RrYy Genotype ¾ R_ ¾ Y_ 9/16 yellow and round Trait Round yellow 3/16 green and wrinkled Genotype 2 ¼ rr ¼ yy 3/16 yellow and wrinkled Trait 2 Wrinkled green 1/16 green and wrinkled (These probabilities were obtained by cross multiplying every combo) o Binomial expansion     Use the formula  P =   (a+b) n   (where a=probability of Trait 1, b = probability of Trait 2, n = 
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This note was uploaded on 01/25/2011 for the course BICD 100 taught by Professor Nehring during the Spring '08 term at UCSD.

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Discussion Section(kathleen) - handout 4 - BICD100Genetics...

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