Question

Take Home Practice Problem In 1923, Bridges and Morgan reported the following data from a three-factor linkage testcross involving chromosome 3 in Drosophila melanogaster. The three loci are ca (claret), e (ebony), and ro (rough). All three mutant phenotypes are due to recessive alleles. 49 Wild type Ebony Claret 395 Rough 119 Ebony, rough 370 Ebony, claret 89 Rough, claret 1 Ebony, rough, claret 66 What is the linkage distance between rough and claret, in cM? A. 10.6 B. 10.7 C. 14.4 D. 19.3 E. 30.0 What is the interference calculated from this data set? A. 0.1 B. 0.3 C. 0.5 D. 0.7 E. 0.9

Answer 1

7 Parental 7 single cross over I (SCOI) Amanging the traits :- claret cca) – 395 Ebonyle) roughero)- 370 Wild type – 49 Ebony, rough, claret - 66 Rough 119 Ebony, claret - 89 Ebony Rough claret - I 7 single cross over II (SCOLI) 7 Double cross over - (DLO) Note – Mats date – ment data – Parental Dco ca - - - e no parental e – – ro Ea Deo find out change in Dco in reference parental trait of e - e so ca scol ca - - - e no - - toca & ca. 80 J Scot linkage distance between drough & claret -x 100 80 & ca & Dco Total progeny (119+89) + (att) 1090 htt) x 100

208 42 x coo 1090 210 x 100 1090 = 19.26 cm linkage distance between not ca is = 19.26cm or 19. 3cm linkage - dist. 610 et so (49+66) + (1+i) x 100 1090 117 x 100 = 10.85 en logo = Interference from this data set Interference - un cofficient of incidence = 1-0.05 0.95 cofficient of ineldence frego of Dco observed frege of Dco expected

freq. of Deo obsen. = 2 logo 0.ool = freq. of Deo exp. = = scosocalt scoero% 19.34. X 10.8% 700 = 0.020 Cofficient of Enei denee = 0.00L 0.020 = 0.05 Interference from this data set is = 0.95 or og