Answer to Question #246516 in Genetics for Tumzaza

Question

In a certain plant, both purple x purple and purple x blue produce purple and blue coloured progeny, but blue x blue gives rise only to blue.

2.1. What does this tell you about the genotypes of blue- and purple-flowered plants [5 marks]

2.2. Which gene is dominant

 

Answer 1

Let allele for blue be - B

Let allele for purple be - b .

BB - homozygous blue .

bb- homozygous purple.

Since it is mentioned in the question that blue gives rise only to blue , it means even a single allele of blue color can give rise to the color in a plant , hence it is the dominant color . Meaning if the gene carries Bb which is heterozygous and BB ,which is homozygous, the progeny plant will be blue

Purple is the recessive color which means two alleles of b are to be present in a gene for purple color to be expressed . That is bb will be purple .

Hence blue is dominant and purple is a recessive color.