Question

It is believed that height of a child depends upon the genes inherited from parents. However, it is often seen that tall parents have short children and short parents have tall children. Find the reason.

Answer 1

There are two types of genes: Dominant and Recessive. The Dominant gene always expresses itself while the recessive one remains suppressed. The recessive is expressed only in homozygous condition...that is, when both the genes are recessive.


Let me give you an example.
Let the dominant Gene for tallness be TT and dominant gene for dwarfness be tt.

Let the father be tall and the mother be short.
Hence genes of the father is TT and that of the mother is tt.

Hence, when they are crossed, we get four offsprings of the following gene combination:

Tt
Tt
Tt
Tt

Thus, all are tall (heterozygous) because there is a dominant gene T, which suppresses the recessive gene t.

Again, when two of these offsprings are crossed, I.e., Tt X Tt
We get four offsprings with the following gene combination:

TT
Tt
Tt
tt

Thus, from two tall parents,

Three tall offsprings are formed (one pure tall and another hybrid tall)
and one SHORT offspring is formed.


Thus in this way, tall parents can give birth to short offsprings.

Hope this helps you. For any problem regarding any subject including Biology, ask me.....
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