F13 lecture 8 v2

# What are the genotypic and phenotypic ratios of the

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Unformatted text preview: 2 46 9 20 15 11 5 Homework 1 review Homework 1 review 3) The Drosophila melanogaster yellow gene is on the X chromosome. yellow/Y males and yellow/yellow females have yellow (lighter than normal) body color. yellow+/Y males, yellow+/yellow females, and yellow+/yellow+ females have wild type body color (i.e. yellow is recessive to yellow+; yellow+ is dominant to yellow). What are the genotypic and phenotypic ratios of the following two crosses. Be sure to state the ratios in each sex. a)  phenotypically yellow+ males crossed to phenotypically yellow females yellow+/Y males x yellow/yellow females -> males 100% yellow body color; 100% yellow/Y -> females 100% yellow+ body color; 100% yellow+/ yellow Homework 1 review b) phenotypically yellow males to yellow/yellow+ heterozygous females yellow/Y males x yellow/yellow+ females -> males 50% yellow body bolor, 50% yellow+ body color; 50% yellow+/Y; 50% yellow/Y -> females 50% yellow body bolor, 50% yellow+ body color; 50% yellow/yellow; 50% yellow/ yellow+ Homework 1 review Homework 1 review Homework 1 review b) What are the coefficient of coincidence and Interference measures in this three gene interval? observed frequency of double recombinants = (14+13)/2940 = 0.009 expected frequency of double recombinants = (rf between A and C)*(rf between C and B) = (0.084)*(0.126) = 0.011 coefficient of coincidence = observed freq of doubles/expected freq of doubles = 0.009/0.0011 = 0.82 interference = 1 - c of c = 1 – 0.82 = 0.18 (positive interference) changes in allele frequency •  can be caused by –  mutaGon –  migraGon (gene ﬂow) –  selecGon –  geneGc driU mutaGons •  base subsGtuGons •  inserGon- deleGons (“indels”) –  may cause frame shiUs in protein coding regions –  transposible element inserGons •  chromosome rearrangements –  inversions –  translocaGons populaGon change by mutaGon alone is very slow mutaGon rates •  generally 1x10- 4 to 1x10- 5 per locus per generaGon •  vary across the genome –  hot spots and cold spots •  vary between species hIp://www.nature.com/scitable/content/19266/ pierce_table_17_3_FULL.jpg migraGon •  migraGon = movement of individuals between populaGons •  gene ﬂow = movement of genes between populaGons •  migraGon can occur without gene ﬂow –  if immigrants don’t succ...
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## This document was uploaded on 02/27/2014.

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