Question

What is the range of values for survival percentage of T^rT^s individuals in Problem 3.7 (Consider a hypothetical locus for tuberculosis resistance/susceptibility with alleles T^r (resistant) and T^s (susceptible). When exposed to the tuberculosis pathogen, T^rT^r individuals survive 90% of the time, and T^sT^s individuals survive 30% of the time. What is the value for survival percentage of T^rT^s individuals if the locus exhibits: a. complete dominance and T^r is the dominant allele? b. complete dominance and T^s is the dominant allele? c. no dominance?) if the locus exhibits: a. partial dominance and T^r is the dominant allele? b. partial dominance and T^s is the dominant allele? c. overdominance and T^r is the dominant allele? d. overdominance and T^s is the dominant allele?

Answer 1

Ans.)

PART A:

Case a : complete dominance and T^r is the dominant allele

Ans: Survival percentage of  T^rT^s is 90%

Explanation: As the allele T^r is completely dominant and survival of individual with homozygous dominant resistance genotype is 90% hence individual allele in heterozygote will produce similar effect.

Case b : complete dominance and T^s is the dominant allele

Ans: Survival percentage of  T^rT^s is 30%

Explanation: As the allele T^s is completely dominant and survival of individual with homozygous dominant susceptible genotype is 30% hence individual allele in heterozygote will produce similar effect.

Case c : No dominance

Ans : Survival percentage of  T^rT^s is 60%

Explanation : As none of the allele are dominant it means both alleles are equally dominant or co-dominant. That means the effect produced will be intermediate of the effect produced by two extreme effects of the two alleles.

PART B :

Case a :  partial dominance and T^r is the dominant allele

Ans: Survival percentage of  T^rT^s is 60%

Explanation: As there is partial domiance of T^r allele, this means it is incomplete dominant . In case of incomplete dominance the phenotypic effect produced by heterozygous is exactly intermediate of the two extreme effects produced.

Case b : partial dominance and T^s is the dominant allele

Ans: Survival percentage of  T^rT^s is 60%

Expalantion: As there is partial domiance of T^s allele, this means it is incomplete dominant . In case of incomplete dominance the phenotypic effect produced by heterozygous is exactly intermediate of the two extreme effects produced.

Case c: overdominance and T^r is the dominant allele

Ans: Survival percentage of  T^rT^s is more than 90%

Explanation: As there is over dominance of T^r allele hence the phenotypic effect produced in heterozygous condition will be more that homozygous T^rT^r allele. There will be more resistance in heterozygotes than in homozygotes dominant resistance.

Case d : overdominance and T^s is the dominant allele

Ans: Survival percentage of  T^rT^s is less than 30%

Explanation: As there is over dominance of T^sallele hence the phenotypic effect produced in heterozygous condition will be more that homozygous T^sT^s allele. There will be more susceptiblity in heterozygotes than in homozygotes dominant susceptible. Hence survival will be less.