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Molecular Basis of Inheritance Class 12 Biology Chapter 4 Questions And Answers Maharashtra Board

Q. 1. Multiple Choice Questions 1. Griffith worked on ………….a. Bacteriophage b. Drosophilac. Frog eggs c. Streptococci Answer. (d) Streptococci 2. The molecular knives of DNA are …………..a. Ligases b. Polymerasesc. Endonucleases d. Transcriptase Answer. (c) Endonucleases 3. Translation occurs in the ………………..(a) Nucleus(b) Cytoplasm(c) Nucleolus(d) Lysosomes Answer. (b) Cytoplasm 4. The enzyme required for transcription is ………………a. DNA polymeraseb. RNA polymerasec. Restriction enzymed. RNAas Answer. (b) RNA polymerase 5. Transcription is the transfer of genetic information from …………..a. DNA to RNAb. tRNA to mRNAc. DNA to mRNAd. mRNA to tRNA Answer. (a) DNA to RNA 6. Which of the following is NOT part of protein synthesis?(a) Replication(b) Translation(c) Transcription(d) All of these Answer. (a) Replication 7. In the RNA molecule, which nitrogen base is found in place of thymine?(a) Guanine(b) Cytosine(c) Thymine(d) Uracil Answer. (d) Uracil 8. How many codons are needed to specify three amino acids?(a) 3(b) 6(c) 9(d) 12 Answer. (a) 3 9. Which out of the following is NOT an example of inducible operon?a. Lactose operonb. Histidine operonc. Arabinose operond. Tryptophan operon Answer. (d) Tryptophan operon 10. Place the following event of translation in the correct sequencei. Binding of met-tRNA to the start codon.ii. Covalent bonding between two amino acids.iii. Binding of second tRNA.iv. Joining of small and large ribosome subunits.A. iii, iv, i, ii B. i, iv, iii, iiC. iv, iii, ii, i D. ii, iii, iv, i Answer. (b) i, iv, iii, ii Q. 2. Very Short Answer Questions: 1. What is the function of an RNA primer during protein synthesis? Answer. During DNA replication, RNA primer provides 3’ OH to which DNA polymerase enzyme can add nucleotides to synthesize new strand using parental strand of DNA as template.[Note : RNA primer has no direct role in protein synthesis.] 2. Why the genetic code is considered as commaless ? Answer. The triplet codon are arranged one after the other on m-RNA molecule without any gap or space and therefore genetic code is considered as commaless. 3. What is genome? Answer. Genome is the total genetic constitution of an organism or a complete copy of genetic information (DNA) or one complete set of chromosomes (monoploid or haploid) of an organism. 4. Which enzyme does remove supercoils from replicating DNA? Answer. Super-helix relaxing enzyme (Topoisomerase) removes supercoils from replicating DNA. 5. Why are Okazaki fragments formed on lagging strand only? Answer. Okazaki fragments are formed only on lagging template as only short stretch of lagging template becomes available for replication at one time. 6. When does DNA replication take place? Answer. In eukaryotes DNA-replication takes place during S-phase of interphase of cell cycle and in prokaryotes. DNA replicates prior to cell division. 7. Define term- codon and codogen. Answer. Codogen is a triplet of nucleotides present on the DNA which specifies one particular amino acid.Codon is a triplet of nucleotides present on the m-RNA which specifies one particular amino acid. 8. What is degeneracy of genetic code? Answer. Genetic code is degenerate as 61 codons code for 20 amino acids, that is two or more codons can specify the same amino acid. E.g. Cysteine has two codons, while isoleucine has three codons. 9. Which are the nucleosomal ‘core’ histones? Answer. Two molecules each of histone proteins, viz. H2A. H2B, H3 and H4 are the nucleosomal ‘core’ histones. Q. 3. Short Answer Questions: 1. Write short note on DNA packaging in eukaryotic cell. Answer. 2. Enlist the characteristics of genetic code. Answer. The characteristics of genetic code are 3. Write a note on applications of DNA finger printing. Answer. Applications of DNA fingerprinting are as follows: 4. Explain the role of lactose in ‘Lac Operon’. Answer. Q. 4. Short Answer Questions: 1. Write a note on Human genome project (HGP). Answer. 1. Human Genome Project (HGP) was initiated in 1990 under the International administration of the Human Genome Organization (HUGO) and it was completed r in 2003. 2. The main aims: 3. Significance: 2. Describe the structure of ‘Operon’. Answer. 3. In the figure below A, B and C are three types of ________. Answer. A, B and C are A : m-RNA, B : r-RNA, C : t-RNA 4. Identify the labeled structures on the following diagram of translation. Part A is the ____________.Part B is the ____________.Part C is the ____________. Answer. Part A is the anti-codon.Part B is the amino acid.Part C is the larger subunit of ribosome. 5. Match the entries in column I with those of column II and choose the correct answer. Answer. Column I Column II A. Alkali treatment ii. Splits DNA fragments into single strands B. Southern blotting iii. DNA transferred to nitrocellulose sheet C. Electrophoresis i. Separation of DNA fragments on gel slab D. PCR vi. DNA amplification E. Autoradiography iv. X-ray photography F. DNA treated with REN v. Produce fragments different sizes Q. 5. Long Answer Questions: 1. Explain the process of DNA replication. Answer. DNA replication is semi-conservative replication. It involves following steps:Activation of Nucleotides: Point of Origin or Initiation point: Unwinding of DNA molecule: Replicating fork: Synthesis of new strands: Leading and Lagging strand: Formation of two daughter DNA molecules: 2. Describe the process of transcription in protein synthesis. Answer. Transcription involves three stages, viz. Initiation, Elongation and Termination.(1) Initiation: (2) Elongation: (3) Termination:When RNA polymerase reaches the terminator site on the DNA, both enzyme and newly formed m-RNA (primary transcript) gets released. 3. Describe the process of translation in protein synthesis. Answer. Translation involves the following steps:1. Activation of amino acids and formation of charged t-RNA (t-RNA – amino acid complex):i. In the presence of an enzyme amino acyl t-RNA synthetase, the amino acid is activated and then attached to the specific t-RNA molecule at 3’ end to form charged t-RNA (t-RNA – amino acid complex). ii. ATP is essential for the reaction. 2. Initiation of Polypeptide chain: 3. Elongations of polypeptide chain:Addition of amino acid occurs in 3 Step cycle-i. Codon recognition.Anticodon of second (and subsequent) amino acyl t-RNA molecule recognizes and binds with