1 4 (4 4 256 Exam # 1 Study Guide Wording to look out for: OR means addition AND means multiplication If the question asks for allele frequency that means you are given p2 or q2 If it tells you the allele frequency it wants you to give p2 or 2pq or q2 p is the frequency of the dominant allele Pedigrees: Recessive, assume all direct ancestors are carriers Brother and sister inbreed co-efficent: 1/4 Half siblings: 1/8 First cousins: 1/16 Mendels: Monohybrid cross Aa x Aa 3:1 Monohybrid test cross Aa x aa 1:1 Dihyrbid cross AaBb x AaBb 9:3:3:1 Dihyrbid test cross AaBb x aabb 1:1:1:1 Test problems Two normal parents produce a child affected with an autosomal recessive disease. They want to have 3 more children. What are the chances that 1 or more of the next three children will be affected? 3! (1 ) 1 3 )2 + 3! (1 )2(3 )1 + 3! (1 )3(3 )0 = .578 !2! 2!1! 4 4 3!0! 4 4 Polygenes control the length of an ear of corn. The corn length ranges from 8 cm to 40 cm long. Corn with 40 cm length is crossed to an 8 cm long corn. The F1 yields 24 cm ears. The F1 is crossed and yields corn ranging from 8 cm to 40 cm. The 8 cm and 40 cm occur at a frequency of about 1/256. How many loci are involved? (1 )N = 1 N = 4 What is the contribution in ear length for each contributing allele? Range = 40−8 = 4 cm N umber of Alleles 2*4 If the F1 (24 cm) plant is crossed to 8 cm, how frequently do you expect 32 cm? Never. You can’t get a value higher than what you are crossing Polydactyly is a dominant trait. In a particular village it occurs at a frequency of 1/40 newborns. What is the allele frequency of polydactyly? GENE 301 1st Edition4 3 2 2 ( ) 5 2 2 ( ) p2 + 2pq + q2 = 1 p2 + 2pq = 0.025 q2 = 1 − 0.025 q= .987 p+q = 1 p+.987 = 1 p=.013 Allele frequency of polydactyly is 0 .013 Carnations come in three colors. Red, white, and pink. They are incompletely dominant at a locus with 2 alleles. If a field contains 240 red (RR), 480 pink (Rr), and 280 white (rr) (total=1000), what is the frequency of the R allele? Use the most accurate method * 2 +480 240 2000 = 0.48 In a population of Canadian Eskimos, the autosomal recessive gene for albinism exists at an allele frequency of 0.04. What proportion of individuals are expected to be heterozygous? .04=q 1-.04= 0.96 which is p. 2*(.04(.96)) = 0.0768 Of what frequency is it expected for an albino offspring from a brother and sister mating? 0.042 + (1 )(0.04(0.96)) = 0.0112 Alkaptonuria is an autosomal recessive disorder and has an allele frequency of 0.05 in the population. What will be the allele frequency of the recessive after one generation of modern selection (W22 = .5, W 11 = 1, W 12= 1) against the recessive? 2 * 0.05 (.5)+.95 .05 = .952+2(.95(.05))+.052(.5) 0.125 Five loci defined by micro-arrays are known to contribute to meat quality in cattle. Premium meat quality occurs when 8 or more alleles at 5 loci are of the contributing type. If the following genotypes are crossed, what is the probability of the first offspring has 8 or more contributing alleles. AaBbccDDEe andAABBCCDdEE 4! (1 )3(1 )1 + 4! (1 )4(1 )0 = 0.3125 !1! 4!0! 2 2 Suppose you have a female, genotype AaBBccDdEE with 6 contributing alleles. You have the choice to cross with 4 different bulls. Which is the most likely to yield offspring with 8 or more contributing alleles? ABbccDDEe 4! 1 4 4!0! 2 = 1/16 = 0.0625 AABBCCddee 2! means that it cannot happen AaBbCcDdEE 6! (1 )5(1 )1 + 6! (1 )6 = 0.10937 AABBCcDdee 4! 1 4 4!0! 2 !1! = 0.0625 6!0!