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Molecular Basis of Inheritance

Short Answer Type

131.

The base sequence in one of the strands of DNA is TAGCATGAT.

(i) Give the base sequence of its complementary strand.

(ii) How are these base pairs held together in a DNA molecule?

(iii) Explain the base complementarity rules. Name the scientist who framed this rule.

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132.

What is a cistron?

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Long Answer Type

133. How do m-RNA, t-RNA and ribosomes help in the process of translation?

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134.

Describe how the lac operon operates, both in the presence and absence of an inducer in E.coli.

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Short Answer Type

135.

(a) Draw a neat labelled diagram of a nucleosome.

(b) Mention what enables histones to acquire a positive charge.

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136. List the salient features of double helix structure of DNA.

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137. How are the structural genes activated in the lac operon in E.coli

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138. Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles.

Plasmodium (malarial parasite) requires two hosts – human and mosquitoes to complete its life cycle. Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. The parasites initially multiply within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs leads to release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days. When a female Anopheles mosquito bites an infected person, these parasites enter the mosquito’s body and undergo further development. The parasites multiply within the mosquito’s body to form sporozoites that are stored in their salivary glands. When these mosquitoes bite a human, the sporozoites are introduced into his/her body, thereby initiating the another cycle.