Molecular Basis of Inheritance Class 12 Biology MCQ With Solutions

Q.2. Histones are rich in

(a) lysine and histidine (b) valine and histidine
(c) arginine and lysine (d) arginine and histidine

Answer

(c): Histones are the alkaline protein which wrap DNA into a condensed form. Histones consist of two basic (positively charged) amino acids arginine and lysine

 

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Q.3. If Escherichia coli grown in ¹⁵N medium for several generation and after that is allowed to grow in ¹⁴N medium for one generation. Which of the following would be correct with regard to the first generation bacteria in ¹⁴N medium?

(a) Both strands of DNA would have different density and do not resemble parent DNA.
(b) Both strands of DNA would have different density but resemble parent DNA.
(c) Both strands of DNA would have same density and resemble parent DNA.
( d ) Both strands of DNA would have Ansame density but do not resemble parent DNA.

Answer

(a): The Escherichia coli grown in ¹⁵N medium would be fully labelled with ¹⁵N but when it is allowed to grow in ¹⁴N medium, it would have one parent strand and one new strand, as the DNA replication is semi conservative. The new strand would be labelled with ¹⁴N. Therefore, the two strands of DNA molecule of the first generation bacteria would have different density and do not resemble parent DNA.

 

Q.4. Which of the following pairs of codons includes all three chain termination codons?

(a) TAG, UAA, AGA (b) UAG, UGA, UAA
(c) AGT, TAG, UGA (d) GAT, UAG, AGT

Answer

(b): UAA (Ochre), UAG (Amber) and UGA (Opal) are non- sense codons which do not code for any amino acid, therefore cause the termination of translation.

 

Q.5. The prokaryotic genome differs from the eukaryotic genome as

(a) the genes are organised into operons in eukaryotes.
(b) the prokaryotes have more complexed DNA with histones
(c) the DNA is circular and single stranded in prokaryotes
(d) the prokaryotes have special structure called nucleosomes.

Answer

(c): Genome refers to the total sets of chromosomes carried by each cell of the organism. In prokaryotes, the genome is circular and single stranded DNA. It has no association of histones. It remains in direct contact with the cytoplasm. The eukaryotic genetic material is linear and double stranded DNA It is associated with histone proteins to form nucleosome unit. It is separated by a nuclear membrane

 

Q.6. Anticodon is

(a) paired triplet of bases on mRNA
(b) unpaired triplet of bases on rRNA
(c) an unpaired triplet of bases in an exposed portion of tRNA
(d) an unpaired triplet of bases in an exposed portion of mRNA

Answer

(c): Anticodon is a triplet of nucleotide bases in transfer RNA that identifies the amino acid carried and binds to a complementary codon in messenger RNA during protein synthesis at a ribosome.

 

Q.7. Avery, MacLeod and McCarty identified the transforming principle of Streptococcus pneumoniae as

(a) RNA (b) DNA
(c) protein (d) polysaccharide.

Answer

(b): Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA (not proteins) can transform the properties of cells, clarifying the chemical nature of genes. They identified DNA as the “transforming principle” while studying Streptococcus pneumoniae, bacteria that can cause pneumonia.

 

Q.8. Which of the following is an incorrect statement?

(a) DNA fingerprinting involves identifying similarities in repetitive DNA.
(b) In prokaryotes, the DNA is organised into a circular chromosome, supercoiled within the nucleoid region of the cell cytoplasm.
(c) François Jacob and Jacque Monod discovered lac operon.
(d) VNTR is a kind of minisatellite DNA.

Answer

(a): DNA fingerprinting is based on the identification of differences in repetitive DNA sequences. These repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation.

 

Q.9. Consider the following statements.

(i) The lac operon model has three elements regulator, operator and structural genes.
(ii) The prokaryotic DNA has both exons and introns.
(iii) RNA polymerase binds to promoter and initiates transcription.
(iv) The regulation of lac operon in E. coli occurs at epigenetic level.

(a) (i) and (iii) are correct.
(b) (i) and (ii) are correct.
(c) (i), (ii) and (iii) are correct.
(d) (ii) and (iii) are correct.

Answer

(a): Eukaryotic genome has unique features of exon – intron organisation of protein coding genes, representing coding sequence and intervening sequence that represents the functionality of RNA part inside the genome. The regulation of  gene expression in prokaryotic cells occurs at the transcriptional level.

 

Q.10. Read the given statements with regard to DNA replication and identify the correct one.

(a) The double helix in one daughter cell consists of two strands that were originally in the parent cell, while the double helix in the other daughter cell consists of two newly made strands.
(b) The two strands of the double helices in both daughter cells consist of segments of new and parental DNA.
(c) The double helices in each daughter cell consists of one parental strand and one newly made strand.
(d) None of these

Answer

(c): DNA replication occurs in a “semiconservative” fashion. According to the semiconservative replication model, the two original DNA strands (i.e., the two complementary halves of the double helix) separate during replication; each strand then serves as a template for a new DNA strand, which means that each newly synthesised double helix is a combination of one old (or original) and one new DNA strand. Therefore, the two daughter cells receives DNA having one parental strand and one new strand.

 

We hope the MCQs for the CBSE Class 12 Biology Chapter 5 on Molecular Basis of Inheritance are helpful for your board exam preparation.

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