12th biology chapter 4 MCQs ( Molecular Basis of Inheritance )

Multiple Choice Questions

1. Griffith worked on .............
    a. Bacteriophage
    b. Drosophila
    c. Frog eggs
    d. Streptococci

Answer : d 
Explanation : Griffith used two strains of pneumococcus (Streptococcus pneumoniae) bacteria which infect mice – a type III-S (smooth) which was virulent, and a type II-R (rough) strain which was nonvirulent.

2. The molecular knives of DNA are …………..
    a. Ligases
    b. Polymerases
    c. Endonucleases
    d. Transcriptase

Answer : c ( Endonucleases )

3. Translation occurs in the ...............
    a. Nucleus
    b. Cytoplasm
    c. Nucleolus
   d. Lysosomes

Answer : b ( Cytoplasm ) 
Explanation : In a eukaryotic cell, transcription occurs in the nucleus, and translation occurs in the cytoplasm.

4. The enzyme required for transcription is ..................
    a. DNA polymerase
    b. RNA polymerase
    c. Restriction enzyme
    d. RNAase

Answer : b

Explanation : RNA polymerase is the main transcription enzymeTranscription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins). 

5. Transcription is the transfer of genetic information from ..............
    a. DNA to RNA
    b. tRNA to mRNA
    c. DNA to mRNA
    d. mRNA to tRNA

Answer : 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 : Replication

7. In the RNA molecule, which nitrogen base is found in place of thymine?
    a. Guanine
    b. Cytosine
    c. Thymine
    d. Uracil

Answer : Uracil 

8. How many codons are needed to specify three amino acid?
    a. 3
    b. 6
    c. 9
    d. 12

Answer : 3
Explanation : Answer and Explanation: Three codons are needed to specify three amino acidsCodons can be described as messengers that are located on the messenger RNA (mRNA). It is a sequence of three nucleotides that code for one specific amino acid; therefore, every three nucleotides represent one codon

9. Which out of the following is NOT an example of inducible operon?
    a. Lactose operon
    b. Histidine operon
    c. Arabinose operon
   d. Tryptophan operon

Answer : Tryptophan operon 
Explanation : Explanation: Lactose operon, galactose operon and maltose operon are the examples of inducible operon.

10. Place the following event of translation in the correct sequence
    i. 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, ii
    C. iv, iii, ii, i
    D. ii, iii, iv, i

Answer : C