Question

1.) Explain why linkage measurements are more accurate for two genes that are close together than two genes that are farther apart. 2.) A female poodle with green eyes (recessive) and yellow spots on her tongue (recessive) was bred with a male poodle who was the wild-type phenotype but hybrid genotype for those same two traits. In a series of litters, this breeding pair gave birth to the following 85 puppies: 39 Normal eyes, normal tongue 36 Green eyes, yellow-spot tongue 6 Green eyes, normal tongue 4 Normal eyes, yellow-spot tongue a.) If these two genes were unlinked, given the way the cross was constructed, what ratio would you expect to see among the four categories of offspring shown here? b.) Which categories of dogs are "parental types" and which are recombinant types? C.) Are these two genes linked? If so, how far are they from each other (in CM)? d.) Would a non-crossover (NCO) and a double-crossover (DCO) event look different from each other in this cross? Why or why not? e.) If these two genes were very tightly linked, just 0.1 CM away from each other, what is the most likely outcome of these 85 puppies in terms of the categories above?

Answer 1

Answer:

Genes enes are arranged linearly on chromosomes. Morgan proposed that different gene havrs exhibited different linkage rates so close tog two genes are less likely will be separated by recombination event. That is crossing over two genes increases with the distance between gene increases together close crossing over between Genes that are close to gether When genes are located on the same chromo- - somes that are close they do not separate They always inherited together due to the absence of crossing over For example : - Red eye. Red eye, X Purple eye, Normal winged & Vestigial winged 6 AABB aabb ( Homozyg ous paranto) lu AB AB ab ab (Gametes) Dropophila F Gene - / ABab/ - Matlon ( Maßb Test cross F X aabb (recessive parent) AB b ab offspring - ABab ab Abab abab 11

P. No. 2 Here truit gives test crom lil independently d'hybrid ie, they ratio 3:1 and donot anod caterhady Genes are far apart - When genes are for they have tendency to separate due to crossing over i.e., assort independently. Example :- Red eyed x Purple eyed, Normal wings Vestigial wings AABB aabb AB AL ab ab f, Gene- -lation Test Cross Aa Bb E x AaBb x Ab aB ab parent recessive aabb AB ab : aabb abab 1 : Generation AaBb Aabb expected ratio 1 1 Lunexpected ratio q : they produced recombinant to parental due to Here type crossing in addition over ..