Molecular Inheritance and Gene Expression : 12th Class Biology Q Ans Lesson 23 – NIOS

Molecular Inheritance and Gene Expression : 12th Class Biology Q Ans Lesson 23 – NIOS

Molecular Inheritance and Gene Expression : 12th Class Biology Q Ans Lesson 23 - NIOS

INTEXT QUESTIONS 23.1

  1. Expand the abbreviation DNA.
    Ans. Deoxyribonucleic acdi
  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 replicaiton5′ to 3′ or 3′ to 5′?
    Ans. In 5’-3’ direction
  2. What is a primer ……………. a DNA molecule or an RNA molecule?
    Ana. 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 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 synthesised during transcription?
    Ans. Cistronic DNA
  3. What is a codon? What is meant by ‘code is degenerate’?
    Ans. 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.
    …………………………………………………………………………………………………………….
  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 is called mutation. When in a DNA sequence a purine is replaced by purine and pyrimidine is replaced by pyrimidine.
  3. Why is “silent mutation” called so? Heredity
    Ans. A silent mutation in a gene does not bring about a change in the synthesis of the coded protien.
  4. What are mutagens?
    Ans. Agents that cause mutation in the genetic material are called mutagens. Mutagens belong to two categories
    a) Radiations : x-ray, UV rays, α radiations.
    b) Chemical : Mustard gas, Actinomycin D
  5. Name a chemical which causes mutation in the heredity material.
    ………………………………………………………………

TERMINAL EXERCISES

  1. How did Hershey and Chase prove that DNA is the hereditary material?
  2. Explain (i) Transduction and (2) Lysogeny
  3. Describe the Watson and Crick model of DNA.
  4. Explain how replication takes place.
  5. Write a note on Central Dogma
  6. State the properties of the genetic code.
  7. Explain transcription in Eukaryotes and processing of hnRNA.
  8. What do you mean by regulation of genes?
  9. Explain how the lac operon gets switched on in the presence of lactose in E.coli.
  10. Name three levels at which regulation takes place in a eukaryotic cell.
  11. Write notes on :
    (i) Types of mutations
    (ii) Okazaki fragments
    (iii) Chain termination during translation

NIOS 12th class biology Q Ans

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Himanshu Kumar

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