Question

1. If a red flower (RR) and a white flower (rr) were crossbred, resulting in 100% Rr, what phenotypes would be seen according to the rules of incomplete dominance? 2. What phenotypes would be present in the scenario above according to the rules of codominance? 3. What is the best way to remember the difference between incomplete dominance and codominance?

Answer 1

Answer: 1) The phenotype of Rr is Pink according to incomplete dominance.

Incomple dominance occurs when none of the alleles is completely dominant over the other, resulting in blending of the phenotype from the parents. When a red (RR) and a white flower (rr) are crossbred, they result in Rr that is a pink phenotype.

2) According to Codominance, the phenotype of Rr is Red and White flower.

Codominance occurs when both the alleles are equally expressed. In this case allele for Red (R) and white (r) phenotype are expressed equally giving Red and White flower.

3) In Codominance, both the alleles are visible in the hybrid and in Incomplete dominance, intermediate (blend of parental) phenotype is visible in the hybrid.

Answer 2

Answer:

1. Pink flowers

2. Red and white flowers

3. Incomplete dominance is a blending of both parental phenotypes while co-dominance is a simultaneous expression of both parental phenotypes.

Explanation:

Incomplete dominance and Co-dominance are both non-mendelian patterns of genetic inheritance i.e. they do not follow the principle of inheritance (Law of dominance) as discovered by Mendel.

Incomplete dominance is a genetic scenario in which one allele of a gene responsible for a trait is incompletely dominant over the other allele, hence, both alleles form an intermediate phenotype that is different from both parents' phenotypes.

Co-dominance, on the other hand, is another genetic scenario in which the two alleles of a gene are neither dominant nor recessive to one another, hence, they are both phenotypically expressed in that gene. The two alleles are said to be co-dominant.

According to this question involving a gene coding for flower colour, one allele codes for red color (R) while the other for white (r).

1) Based on the principles of Incomplete dominance, both alleles (R and r) will form an heterozygote (Rr) with an intermediate phenotype (pink) different from both parental phenotypes. This pink color is a blending of both the red and white colors.

2) Based on the principles of co-dominance, both alleles (R and r) are both dominant, hence, will be expressed together in the gene. Hence, the resulting heterozygote offspring (Rr) will possess both red and white colours on its flower.

3) Incomplete dominance and Co-dominance are different in the sense that Incomplete dominance produces an offspring that has an intermediate phenotype which is a blending of both parental phenotypes while co-dominance results in an offspring that possesses both parental phenotypes simultaneously i.e. both parents' phenotypes are expressed in the heterozygote offspring.