Question

When Mendel crossed pure breeding peas having purple flowers with pure breeding peas having white flowers, all of the offspring had white flowers. These results mean that white flower color is the:

a.) genotype.

b.) dominant phenotype.

c.) recessive phenotype.

d.) mode of inheritance.

Answer 1

The correct answer is : b.Dominant phenotype.

In case of a dominant allele it masks the effect of the recessive allele. So phenotypic trait of the recessive allele can't be expressed . So dominant phenotype is shown. In case of peas white coloured flower is the domaint trait and purple colour trait is the recessive trait. So whenever the cross occurs between these two trait dominant trait is expressed. Apart from that when two pure breeds are crossed with each other, dominant phenotype is expressed in the offspring. Punnett square for the cross is given below-

لياليا واوی Purce breeding white flowerced pea Purce breeding purple Flowerced pea - wow So, when the cross occures W لدا فیلد) we ww (white) (white) فیلد) فی ww (white) | (white As was the dominant allele the phenotype of all these offsprings become white. So, white å the dominant phenotype.

Why other options are not correct:

a. Genotype: Genotype means the genetic constitution of an individual. Colour of pea plant is an observable characteristics. So colour of pea flower is phenotype. The genotype of pea plant based on flower colour may be WW,Ww or ww (W- white pea flower allele, w- puple pea flower allele)

C. Recessive phenotype: After crossing two pure breeds dominant phenotype is shown. As after crossing all the plants had white flower, it is the dominant phenotype. If it had been a recessive phenotype, we wouldn't find any white flower pea plant after crossing of two pure breeds.

D. Mode of inheritance: ​​​​​​Dominant or recessive allele is responsible for mode of inheritance. After a cross generally a dominant phenotype is shown if a single dominant allele is present. So dominant phenotype is more appropriate than mode of inheritance.