Explain the molecular basis for occurrence of white flowers in peas.

Explanation

(i) In 2010, the gene responsible for regulating flower colour in peas were identified by an international team of researchers.
(ii) It was called Pea Gene A which encodes a protein that functions as a transcription factor which is responsible for the production of anthocyanin pigment. So the flowers are purple.
(iii) Pea plants with white flowers do not have anthocyanin, even though they have the gene that encodes the enzyme involved in anthocyanin synthesis.
(iv) Researches delivered normal copies of gene A into the cells of the petals of white flowers by the gene gun method. When Gene A entered in a small percentage of cells of white flowers it is expressed in those particular cells, which accumulated anothocyanin pigments and became purple.
(v) In white flowers the gene A sequence showed a single-nucleotide change that makes the transcription factor inactive. So the mutant form of gene A do not accumulate anthocyanin and hence they are white.