In a species of plants, flower petal colour is determined by one gene. Red colou
ID: 278229 • Letter: I
Question
In a species of plants, flower petal colour is determined by one gene. Red colour is not dominant to white colour and a cross between a TRUE red and a TRUE white variety yields an F1 that is red with white patches (i.e., F1 is both red and white)?
Genotype of TRUE red variety is:…… ………………… (1 mark)
Genotype of TRUE white variety is:……… …………….. (1 mark)
Genotype of F1 is:………… ………………. (1 mark)
This phenomenon refers to… ……………(1 mark)
Provide a genetic explanation for the above results (3 marks).
Provide a genetic (3 marks) and biochemical explanation (draw diagram; 5 marks) for the above results.
Explanation / Answer
Genotype of true red variety is RR
Genotype of true white variety is rr
The F1 generation having both red and white colour having a genotype of Rr
The phenomenon is incomplete dominance.
It is a form of intermediate inheritance where one allele for a specific trait is not completely expressed over its paired allele. It results, a third phenotype that expres physical trait of combination of the phenotypes of both alleles.
It is seen in snapdragon, where red x white (RR×rr) results
RR-red rr-white Rr-pink. The pink shows incomplete dominance.