Question

In roses,the long stem is dominant over short stems. A Homozygous long-stemmed plant is crossed with a homozygous short-stemmed plant. What percentage of the resultant rose plants will have long stems in second generation? Workout with punnets checker board and find the phenotypic and genotypic ratio of F2 generation plants and state the law of dominance

Answer 1

Answer:

75% long stem

Ratio of phenotype-3:1,genotype -1:2:1

Law of dominance-see book

Answer 2

Long stem dominant over Short stems.

Explanation:

(Parental gen)    TT                              X                     tt

(Homozygous long stem plant)                          (Homozygous short stem plant)

(F1 generation)                                  Tt

 

(Self pollination)                         Tt       X      Tt

(F2 generation)                         TT        Tt          Tt           tt

Here:

TT: Homozygous dominant long stem plant

Tt: Heterozygous dominant long stem plant

tt:   Homozygous recessive short stem plant

(a) In second generation, 75 %  of rose plants will have long stem plants.

(b) Following the punnet checker board, the phenotypic ratio of F2 generation plant is 3:1 and the genotypic ratio is 1:2:1.

(c) Law of Dominance: This law sates that in a pair of contrasting traits the allele that is expressed is dominant whereas the allele that is not expressed is recessive.