Question 2 (5 pts). In roses, two gene loci on an autosomal chromosome are 30cM

ID: 219993 • Letter: Q

Question

Question 2 (5 pts). In roses, two gene loci on an autosomal chromosome are 30cM from each other. At locus 1, the E allele for red flower color is completely dominant to the e allele for pink flower color. At locus 2, the G allele for thorns is completely dominant to allele g for thornless. A particular rose cultivar, true-breeding for red flower and thorns, is crossed to cultivar 2, true-breeding for pink flowers and thornless. The F1 generation is testcrossed with cultivar 2 and 300 testcross progeny are produced.

What is the expected frequency of gametes of genotype EG produced by the F1-generations plants?

When the F1-generation plants produce gametes, what is the expected frequency of recombinant gametes?

In the testcross progeny, how many plants are expected to have pink flowers and be thornless?

In the testcross progeny, how many plants are expected to have pink flowers and thorns?

e. If the two loci were not linked, and segregated independently from each other, how

many plants would be expected to have pink flowers and thorns in the testcross progeny?

Explanation / Answer

Answer:

a). 35%

b). Recombinant gametes = 30%

Distance between the genes (cM) = Recombination frequenc (%)

c). Pink, thornless---35%

d). Pink, thorn-15%

e). Pink flowers and thorns = 25%

If the genes are not linked and assort independently, all phenotypes are produced in equal proportions.

Explanation:

Red, Thron (EG/EG) x Pink, Thornless (eg/eg)---P1

EG/eg(red, thorn)-------------------F1

F1 x eg/eg (tester)----------------------------------Testcross

EG/eg x eg/eg

EG (35%%)

EG / eg(35%%)—Red, thorn

Eg(15%)

Eg / eg( (15%)---Red, thornless

eG(15%)

eG / eg( (15%)---Pink, thorn

eg(35%)

eg / eg( (35%)---- Pink, thornless

If the genes are not linked….

EG/eg x eg/eg

EG (25%)

EG / eg(25%%)—Red, thorn

Eg(25%)

Eg / eg( (25%)---Red, thornless

eG(25%)

eG / eg( (25%)---Pink, thorn

eg(25%)

eg / eg( (25%)---- Pink, thornless