You may use additional sheets but remember to label all your answers . Read each

Question

You may use additional sheets but remember to label all your answers . Read each question very carefully. TOTAL POINTS-50 PTS Topic: Mendel's Principles and Meiosis 1. Mice can differ in coat color (olack or brown) and nose twitchiness (twitchy or non- twitchy (chill). The following matings were done, giving the indicated progeny mating 2 mating 1 brown twitchy x brown twitchy brown twitchy x brown non-twitchy offspring indluded the phenotypes below (not necessarily in equal proportions): black twitchy brown twitchy black non-twitchy brown non-twitchy black twitchy brown twitchy black non-twitchy brown non-twitchy (a) which are the dominant phenotypes? how can you tell? 12 pts] b) What are the parental genotypes in each of the two matings? Assuming independent assortment, what are the expected proportions of the progeny phenotypes in each of the two matings? 4 pts]

Explanation / Answer

a. The dominant phenotype will be brown and twitchy. Here the progeny includes black colour also which is only possible if brown colour is dominant. If brown colur would be ressesive it means the parental genotype would be homozygous recessive which will never produce black progeny and same with twitchy also. Thus the brown and twitch are dominant phenotype.

b. In first mating the parental genotypes will be BbTt X BbTt and for second mating the genotype will be BbTt X Bbtt. Thus, the proportions of phenotype in first mating will be 9:3:3:1 and in second mating the proportion will be 3:3:1:1 according to independent assortment law of Mendelian genetics.

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