Answer to Question #163130 in Genetics for Ambreen Qayyum

Question

Two genes ‘d’ and ‘t’ are assumed to show linkage as well as produce recombinants upto 30%. If dd/ dd individual is crossed with one which is tt/tt. What genotype will produce in first filial generation? Also give the possible meiotic products produced by first generation. If a test cross is performed what phenotypes and genotypes will produced in progeny.

Answer 1

Two genes ‘d’ and ‘t’ are assumed to show linkage as well as produce recombinants upto 30%. If dd/ dd individual is crossed with one which is tt/tt. What genotype will produce in first filial generation? Also give the possible meiotic products produced by first generation. If a test cross is performed what phenotypes and genotypes will produced in progeny.

Solution:

P: dd/dd x tt/tt

G1: 100% dd/tt (because both chromosomes of one parent cell have the same set of genes so the set doesn’t change after crossing over)

Possible meiotic products of G1: dd, tt, dt (because chromosomes of cell have different sets of genes and the sets would change after crossing over)

Test cross assumes crossing organism with dominant phenotype and unknown genotype with organism with recessive genotype and phenotype. The prediction of phenotype and genotype of G1 progeny is impossible due to the lack of information about what gene is dominant and what trait it induces.

Answer:

First generation genotype: dd/tt

First generation possible meiotic products: dd, tt, dt