23 Molecular Inheritance and Gene Expression

NIOS Biology Intext Solutions Chapter 23

INTEXT QUESTIONS 23.1

1. Expand the abbreviation DNA.

Ans: Deoxyribonucleic acid

2. Name the scientists who confirmed that DNA was the genetic material in bacterial transformation.

Ans: Avery, McLeod, and McCarty

3. Name the sugar and the nitrogenous bases found in DNA.

Ans: Deoxyribose, Adenine, Guanine, Thymine, Cytosine

INTEXT QUESTIONS 23.2

1. In which direction does DNA polymerase proceed to catalyse DNA replication 5′ to 3′ or 3′ to 5′?

Ans: In 5’-3’ direction

2. What is a primer, a DNA molecule, or an RNA molecule?

Ans: RNA molecule

3. Name the four enzymes needed for DNA replication.

Ans: Helicase, DNA polymerase, DNA ligase, Topoisomerase

4. Which enzyme joins the Okazaki pieces to form a complete DNA strand?

Ans: DNA ligase

INTEXT QUESTIONS 23.3

1. What is the central dogma in molecular Biology?

Ans: The transfer of information from genes to the site of protein synthesis constitutes the central dogma.

2. Which molecule is synthesized during transcription?

Ans:  Cistronic DNA

3. What is a codon? What is meant by ‘code is degenerate’?

Ans: A Sequence of three bases in the genes.

4. Where in the cell does translation occur?

Ans: Nucleus

5. Name the three types of RNA that participate in protein synthesis.

Ans: mRNA, tRNA, hnRNA

INTEXT QUESTIONS 23.4

1. Name the components of an operon.

Ans: The operon includes certain genes lying close together on the chromosome next to the regulator gene i, and includes promoter gene p, which RNA polymerase identifies at the time of transcription; operator gene, o, which switches on structural genes z, y, and a coding for the enzymes, Galactosidase, Permease, and Transacetylase.

2. What is mutation? When is a mutation called a transition mutation?

Ans: A heritable change in the structure, content, and organization of genetic material when in a DNA sequence a purine is replaced by a purine and a pyrimidine is replaced by a pyrimidine.

3. Why is “silent mutation” called so? 

Ans: A silent mutation in a gene does not bring about a change in the synthesis of the coded protein.

4. What are mutagens?

Ans: Agents that cause mutation in the genetic material are called mutagens.

5. Name a chemical that causes mutation in the hereditary material.

Ans: Mustard gas, Actinomycin D

Additional Study Materials

• Chapter 19 Reproduction in Plants
• Chapter 20 Growth and Development in Plants
• Chapter 21 Reproduction and Population Control
• Chapter 22 Principles of Genetics