Question

a) Explain how testing a codominant trait in pea plants would have made it more difficult for Mendel to interpret his results.

b) A scientist performs a dihybrid cross. The plant has the following traits: It can either have rough leaves (R) or smooth leaves (r). It can either have wide leaves (W) or narrow leaves (w). The scientist crosses a plant with genotype RrWW with a plant with genotype RrWw.

Fill in the Punnett square below for this cross.

c) The family tree below shows the recessive trait of having attached earlobes. People with attached earlobes are shaded in. Some family members are labeled with numbers.

State the genotype of each family member below. Use “E” for the dominant allele and “e” for the recessive allele.

Number 1:

Number 2:

Number 3:

d) Would it be possible for #4 and #5 to have a child with detached earlobes? Explain.

Answer 1

Answer-

a) Answer- Mandel had performed simple experiments by using pea plants having definite traits of opposite expression as Tall or Dwarf, Round seed or Wrinkeled seeds. He abserved simple dominant recessive relationship between them. According to which, when alleles of two contrasting characters comes together then one of them expresses itself and is called dominant and another alleles remains unexpressed and is called as recessive.

While in case of co-dominance a new phenotype is obtained when two alleles of different expression comes together. And there will be no dominant recessive relationship between such traits. Therefore, testing such traits is difficult for Mandel.

b). Answer-

​​​​​​Genotypic ratios are - 1:1:2:2:1

for c) and d) the family tree is not given