Exam 4: Mapping Eukaryote Chromosomes by Recombination

The three genes,D,E,and F,are closely linked as indicated on the map below.In this region of the genome,there is no interference (the coefficient of coincidence is 1). If a trihybrid with genotype ABC/abc is testcrossed,what is the expected percent of "parentals" within the progeny?

A fruit fly of genotype a⁺/a ^. b⁺/b (parent 1)is crossed to another fruit fly of genotype a/a ^. b/b (parent 2).The progeny of this cross were: Genotype Number of individuals /a\cdot/b 38 a/a\cdotb/b 37 /a\cdotb/b 12 a/a\cdot/b 13 a)What gametes were produced by parent 1 and in what proportions? b)Do these proportions demonstrate independent assortment of the two genes? c)What can be deduced from these proportions? d)Demonstrate the arrangement of the genes on the chromosomes in parents 1 and 2 using the appropriate symbols. e)Draw a diagram or diagrams to explain the origin of the two rarest progeny genotypes.

In loppins (small,diploid invertebrates),chocolate-dependent problem-solving ability is an autosomal recessive trait.You have been hired to map the position of the gene controlling this phenotype (called "lu")using two SSLP markers (called "A" and "B").You first cross two pure-breeding loppins: lu⁺A^{[3 repeats]} B^{[5 repeats]}/lu^+-A^{[3 repeats]} B^{[5 repeats]} X lu^- A^{[6 repeats]} B^{[8 repeats]}/lu^-A^{[6 repeats]} B^{[8 repeats]} The F₁ is then crossed back to the lu^-/lu^- parent.Which of the following results would indicate that the lu gene is much closer to SSLP "A" than to SSLP "B"?

A corn plant known to be hybrid for three linked genes is testcrossed.The progeny phenotypes and frequencies are: +++ 74 abc 70 a++ 44 +bc 50 ++c 4 ab+ 2 a+c 368 +b+ 388 The coefficient of coincidence in this genomic region is: