Question

flower color in snapdragon plants is a character that shows incomplete dominance. Plants with a CRCR genotype have red flowers. Plants with a CWCW genotype have white flowers. Plants with heterozygous genotypes have pink flowers. Two plants were crossed. Nineteen of the offspring plants had pink flowers. Twenty-one of the offspring plants had white flowers. What was the genotypes of the parental plants

Answer 1

Answer: The parental plants has heterozygous genotype (CRCW) and homozygous white genotype (CWCW)

Explanation: Analising the offspring, we have 19 pink flowers and 21 white flowers.

From the question, we know that to be white, the individual has to have CWCW genotype. So one of the allele from the parents must be CW.

Yet, to be pink, the plant has to be heterozygous, which means CRCW. So, the other allele must be CR.

Now, since there are white offspring, one of the parents must has the genotype CWCW, otherwise, there would be a red flower plant.

Therefore, one parent is CWCW and the other is CRCW.

To confirm that, we can cross the genotypes, using a Punnett Square:

            CW          CW

CW    CWCW    CWCW

CR     CRCW     CRCW

From the square, the chance of having genotype CWCW is 50%, which is the same as with CRCW. So, half of these parents offspring will be white and half will be pink. Analising the numbers, 19 out 40 is pink, while 21 out of 40 is white. The proportion is approximately 50/50. So, the crossing represents this genealogy and the parents' genotypes are as described.