Question

2. When a plant homozygous for tall is crossed with a plant homozygous for dwarf, what will be the appearance of the off-springs of a cross of F1 with its tall parent?

Answer 1

ANSWER:

The condition given is that a plant (Homozygous tall) is crossed with a plant (Homozygous dwarf), then the appearance of the plats or saplings at the F₁ generation would be all tall plants.

The plants are homozygous tall, so their alleles will be the same. Consider a plant with tallness TT and a plant with dwarfness tt.

If we cross both plants, we get:

$\ \ \ \ T \ \ \ T \\t\boxed{Tt}\boxed{tT}\\t \boxed{Tt}\boxed{Tt}$

All the F₁ generation plants have a dominant "T". Therefore, all the saplings will be tall.

CONCLUSION - ALL THE SAPLINGS WILL BE TALL.

CONCEPTS USED:

Homozygoes - Homozygous in biology means that both alleles are identical. For example, if it is said that a fruit is homozygous sweet, it has identical sweet traits.

Heterozygous - Heterozygous in biology means that both alleles are not identical, but they are contrasting. For example, if a fruit is heterozygous sweet, it has a allele for sweetness and a allele for other flavours.

Answer 2

The phenotype of the offspring will be in the ratio of tall: short progeny of 3:1.

F1 cross

A homozygous plant is the one that has the similar type of alleles for a given pair. Whereas a heterozygous plant has dissimilar pairs of alleles.

It is given that a homologous tall plant is fused with a homologous short plant.

Let the allele for short be t and the one for tall be T.

Thus, the genotype for  homologous tall =TT

genotype for phenotype short =tt

The tall parent will produce gametes with T allele while the short parent will produce gametes with t allele.

Making a cross diagram for the F1 offspring, we find

The genotype of progeny on crossing =Tt, Tt, Tt and tt

Thus, the ratio for tall: short progeny = 3:1

(#SPJ3)