Chapter 6 – Molecular Basis Of Inheritance

In a DNA strand the nucleotides are linked together by:

• a.glycosidic bonds
• b.phosphodiester bonds
• c.peptide bonds
• d.hydrogen bonds

A nucleoside differs from a nucleotide. It lacks the:

• a.base
• b.sugar
• c.phosphate group
• d.hydroxyl group

Both deoxyribose and ribose belong to a class of sugars called:

• a.trioses
• b.hexoses
• c.pentoses
• d.polysaccharides

The fact that a purine base always pairs through hydrogen bonds with a pyrimidine base in the DNA double helix leads to:

• a.the antiparallel nature
• b.the semiconservative nature
• c.uniform width throughout DNA
• d.uniform length in all DNA

The net electric charge on DNA and histones is:

• a.both positive
• b.both negative
• c.negative and positive, respectively
• d.zero M NIT II: UNIT II: SSTRUCTURAL OLECULAR BASIS OFO TRUCTURAL INHERITANCE ORGANISATION IN P RGANISATION IN PLANTS ANDA LANTS AND ANIMAL NIMALS 37

The promoter site and the terminator site for transcription are located at:

• a.3' (downstream) end and 5' (upstream) end, respectively of the transcription unit
• b.5' (upstream) end and 3' (downstream) end, respectively of the transcription unit
• c.the 5' (upstream) end
• d.the 3' (downstream) end

Which of the following statements is the most appropriate for sickle cell anaemia?

• a.It cannot be treated with iron supplements
• b.It is a molecular disease
• c.It confers resistance to acquiring malaria
• d.All of the above

Which of the following is true with respect to AUG?

• a.It codes for methionine only
• b.It is an initiation codon
• c.It codes for methionine in both prokaryotes and eukaryotes
• d.All of the above

The first genetic material could be:

• a.protein
• b.carbohydrates
• c.DNA
• d.RNA

With regard to mature mRNA in eukaryotes:

• a.exons and introns do not appear in the mature RNA
• b.exons appear but introns do not appear in the mature RNA
• c.introns appear but exons do not appear in the mature RNA
• d.both exons and introns appear in the mature RNA

The human chromosome with the highest and least number of genes in them are respectively:

• a.Chromosome 21 and Y
• b.Chromosome 1 and X
• c.Chromosome 1 and Y
• d.Chromosome X and Y

Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA?

• a.Rosalind Franklin
• b.Maurice Wilkins
• c.Erwin Chargaff
• d.Meselson and Stahl

DNA is a polymer of nucleotides which are linked to each other by 3’-5’ phosphodiester bond. To prevent polymerisation of nucleotides, which of the following modifications would you choose?

• a.Replace purine with pyrimidines
• b.Remove/Replace 3' OH group in deoxy ribose
• c.Remove/Replace 2' OH group with some other group in deoxy ribose
• d.Both ‘b’ and ‘c’

Discontinuous synthesis of DNA occurs in one strand, because:

• a.DNA molecule being synthesised is very long
• b.DNA dependent DNA polymerase catalyses polymerisation only in one direction (5’ → 3’)
• c.it is a more efficient process
• d.DNA ligase joins the short stretches of DNA

Which of the following steps in transcription is catalysed by RNA polymerase?

• a.Initiation
• b.Elongation
• c.Termination
• d.All of the above

Control of gene expression in prokaryotes take place at the level of:

• a.DNA-replication
• b.Transcription
• c.Translation
• d.None of the above

Which of the following statements is correct about the role of regulatory proteins in transcription in prokaryotes?

• a.They only increase expression
• b.They only decrease expression
• c.They interact with RNA polymerase but do not affect the expression
• d.They can act both as activators and as repressors M NIT II: UNIT II: SSTRUCTURAL OLECULAR BASIS OFO TRUCTURAL INHERITANCE ORGANISATION IN P RGANISATION IN PLANTS ANDA LANTS AND ANIMAL NIMALS 39

Which was the last human chromosome to be completely sequenced:

• a.Chromosome 1
• b.Chromosome 11
• c.Chromosome 21
• d.Chromosome X

Which of the following are the functions of RNA?

• a.It is a carrier of genetic information from DNA to ribosomes synthesising polypeptides.
• b.It carries amino acids to ribosomes.
• c.It is a constituent component of ribosomes.
• d.All of the above.

While analysing the DNA of an organism a total number of 5386 nucleotides were found out of which the proportion of different bases were: Adenine = 29%, Guanine = 17%, Cytosine = 32%, Thymine = 17%. Considering the Chargaff’s rule it can be concluded that:

• a.it is a double stranded circular DNA
• b.It is single stranded DNA
• c.It is a double stranded linear DNA
• d.No conclusion can be drawn

In some viruses, DNA is synthesised by using RNA as template. Such a DNA is called:

• a.A-DNA
• b.B-DNA
• c.cDNA
• d.rDNA

If Meselson and Stahl's experiment is continued for four generations in bacteria, the ratio of N15/N15: N15/N14: N14/N14 containing DNA in the fourth generation would be:

• a.1:1:0
• b.1:4:0
• c.0:1:3
• d.0:1:7

If the sequence of nitrogen bases of the coding strand of DNA in a transcription unit is: 5' - A T G A A T G - 3', the sequence of bases in its RNA transcript would be;

• a.5' - A U G A A U G - 3'
• b.5' - U A C U U A C - 3'
• c.5' - C A U U C A U - 3'
• d.5' - G U A A G U A - 3'

The RNA polymerase holoenzyme transcribes:

• a.the promoter, structural gene and the terminator region
• b.the promoter and the terminator region
• c.the structural gene and the terminator region
• d.the structural gene only.

If the base sequence of a codon in mRNA is 5'-AUG-3', the sequence of tRNA pairing with it must be:

• a.5' - UAC - 3'
• b.5' - CAU - 3'
• c.5' - AUG - 3'
• d.5' - GUA - 3'

The amino acid attaches to the tRNA at its:

• a.5' - end
• b.3' - end
• c.Anti codon site
• d.DHU loop

To initiate translation, the mRNA first binds to:

• a.The smaller ribosomal sub-unit,
• b.The larger ribosomal sub-unit
• c.The whole ribosome
• d.No such specificity exists.

In E.coli, the lac operon gets switched on when:

• a.lactose is present and it binds to the repressor
• b.repressor binds to operator
• c.RNA polymerase binds to the operator
• d.lactose is present and it binds to RNA polymerase