Explain wrinkled pea phenotype at molecular level?
Starch is a carbohydrate which is used as energy storage by plants. It exists in two forms- amylopectin and amylose. Amylose has linear structure or straight chain. Amylopectin has a branched structure.
Round peas contain more amylopectin and wrinkled peas contain more amylose.
Wrinkled phenotype is because of the absence of a Starch branching enzyme 1 (SBE1). Starch branching enzyme 1 is important for the formation of branched structure of amlyopectin, which is inactive in wrinkled peas. Therefore, amylopectin is active in round seed and inactive in wrinkled seeds. It cannot form branched amylopectin properly, and thus form linear amylose easily.
Wrinkled pea plants do not store starch because of the absence of SBE1. It contains more free sucrose that is floating around. Osmosis is movement of water from higher concentration of solute to lower concentration. Therefore, water moves inside the peas as it contains more free sucrose and it gives wrinkled appearance.
At the molecular level, r allele of wrinkled peas contains an extra 800 DNA base pairs. It disrupts the coding region of the gene.
Round peas are dominant because it stores more starch. Wrinkled peas is recessive as do not store much starch.