Q5 of 53 Page 32

The pedigree chart given below shows a particular trait which is absent in parents but present in the next generation irrespective of sexes. Draw your conclusion on the basis of the pedigree.


The given pedigree represents an Autosomal recessive trait.Autosomal because the trait is expressed irrespective of sexes. Recessive because it is not expressed in parent generation (carriers of trait) but seen in their offspring’s.

For example Sickle –cell anaemia that can be transmitted from parents to offspring when both the parents are carrier of the gene. The disease is controlled by a pair of allele HbA and HbS. Out of the three possible genotypes only homozygous individuals for HbS (HbSHbS) show the diseased phenotype. Heterozygous (HbAHbS) individuals appear unaffected but are the carrier of the disease as there is 50% probability of transmission of mutant gene to progeny.


More from this chapter

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3

Enlist the steps of controlled cross pollination. Would emasculation be needed in a cucurbit plant? Give reasons for your answer.

 4

A person has to perform crosses for the purpose of studying inheritance of a few traits / characters. What should be the criteria for selecting the organisms?

 6

In order to obtain the F1 generation Mendel pollinated a pure-breeding tall plant with a pure breeding dwarf plant. But for getting the F2 generation, he simply self-pollinated the tall F1 plants. Why?

 7

“Genes contain the information that is required to express a particular trait.” Explain.