In tomatoes, red fruit is dominant to yellow fruit and hairy stems are dominant to hairless (smooth) stems. The two genes controlling these traits are inherited in normal Mendelian fashion and are not linked.
a) Produce a suitable key for this information in terms of the individual alleles of the genes given.
b) What are the possible genotypes of plants showing the following forms:
i) Red fruit and smooth stems
ii) Yellow fruit and hairy stems
iii) Red fruit and hairy stems
c) On crossing a plant with red fruit and hairy stem, with one that was yellow fruit and hairy stem, the following progeny were obtained:
30 red, hairy / 11 red, smooth / 29 yellow, hairy / 9 yellow, smooth
Give a reasoned explanation along with the use of full genetic diagrams to proof your answer, to explain these results in terms of the simultaneous transmission of characteristics.
Ans (a): Dominant alleles are represented in capital letters and recessive alleles are represented in the small letter. In the given condition as red fruit color is dominant over the yellow fruit color so the allele for red fruit color will be represented as "R" and the allele for yellow fruit color will be represented as "r".
Similarly, as the hairy stem is dominant over the hairless or smooth stem so the allele for the hairy stem will be represented as "H" and the allele for the hairless stem will be represented as "h".
Ans (b): Possible genotypes for
(1) Red fruit and smooth stems
RRhh or Rrhh
(2) Yellow fruit and hairy stems
rrHH or rrHh
(3) Red fruit and hairy stems
RRHH, RRHh, RrHH, RrHh