Answer to Question #316935 in Genetics for Nhlonipho Manganyi

Question

A herpetologist finds an anuran which has a green hue. This is the dominant

colour trait and therefore the genotype for colour can be either homozygous

(GG) or heterozygous (Gg). In this species of frog body colour that is brown

suggests a recessive phenotype and therefore this genotype would have to be

homozygous for the recessive allele (gg). G represents the dominant allele and g represents the

recessive allele. Using selective breeding techniques, how would the researcher determine the

genotype of the original green anuran? Explain how the results of this would help the researcher

identify the genotype or the original green anuran.

10 marks

Answer 1

The researcher will determine the genotype of the original green anuran in the following way. He needs to do a test cross with a recessive homozygote (brown anuran) and look at the results:

P: GG (green) + gg (brown)

↓

F1: 4 Gg (green)

P: Gg (green) + gg (brown)

↓

F1: 2 Gg (green) + 2 gg (brown)

Thus, if when crossing a green anuran with a brown anuran, all the offspring are green, then the green anuran genotype will be GG, and if the offspring are green and brown with an equal ratio, then the green anuran genotype, respectively, will be Gg.