CBSE Questions for Class 12 Medical Biology Molecular Basis Of Inheritance Quiz 12 - MCQExams.com

Which of the following type of DNA is commonly present in the cells of mammals? 
  • A-DNA
  • B-DNA
  • I-DNA
  • Z-DNA
The two strands of DNA are?
  • Similar in nature and complementary
  • Antiparallel and complementary
  • Parallel and complementary
  • Basically different in nature
DNA polymerases I and II are generally used in DNA replication.
  • For proof reading & repair
  • Adding carbonyl compound
  • Breaking and joining pieces of one DNA strand
  • To cut the helix at certain places
Which of the following is a homopolymer?
  • DNA
  • Protein
  • Cellulose
  • Cholesterol

Which of the following is true about DNA polymerase?
  • It can synthesize DNA in the 5' to 3' direction
  • It can synthesize DNA in the 3' to 5' direction
  • It can synthesize DNA in both directions
  • Depend upon the condition

Select the correct statement:
  • DNA polymerase has high degree of accuracy
  • During DNA replication, only one strand of DNA act as template for synthesis of new strand.
  • Taylor has proved by his experiment that DNA is the genetic material
  • E. coli has $$4.6 \times 10^9$$ bp in its genetic material

Two strands of DNA are held together by _____________.
  • Peptide bonds
  • Phosphodiester bonds
  • S- S bonds
  • Hydrogen bonds
Transfer of information from a molecule of DNA to mRNA called as  ....... process
  • Transcription
  • Translocation
  • Mutation
  • Translation
Deoxyribonucleoside triphosphates serve dual purposes in DNA replication. In addition to acting as substrate, the other function is similar to?
  • DNA polymerase
  • rRNA
  • Topoisomerase
  • ATP
According to finding from the Human Genome Project, there are about 25000 genes but there are amny more different polypeptides. Which of the following processes might explain the discrepancy between number of genes and polypeptides?
(1) Mutations
(2) Post-translational modifications
(3) Crossing over during meiosis
(4) Alternating splicing of RNA transcripts
  • 1 & 2
  • 2 & $
  • 1,3 & 4
  • 3 & 4

The commonly used hosts in HGP ________________.
  • Bacteria and yeast
  • Bacteria and fungi
  • Protozoa and bacteria
  • Plants and fungi
Which of the following statements is not incorrect?
  • According to Watson-Crick model, DNA exists as a double helix, in which two strands of polynucleotides are parallel i.e. run in same direction.
  • All types of pyrimidines are present in DNA, while only one type of pyrimidine is present in RNA
  • In a nucleic acid a phosphate moiety links the $$3'$$- carbon of one sugar of one nucleotide to the $$5'$$ carbon of the sugar of succeeding nucleotide
  • In a nucleic acid, the bond between the phosphate and hydroxyl group of sugar is a glycosidic bond
DNA polymerase links nucleotide by forming which type of bond.
  • Phosphodiester bond
  • Hydrogen bond
  • Glycosidic bond
  • Ester bond
Find the nucleotide sequence of the MRNA which codes for the sequence of amino acids - 'Met - Leu - Val - Arg - Ala' and choose the correct option from below :
  • AUG - GAU - GAA - UAU - UGU
  • AUG - GAU - GAA - CGU - GCC
  • AUG - CUA - GUG - UAU - UGU
  • AUG - CUA - GUG - CGU - GCC
Correct sequence for Alanine code is
  • GCU, GCC, GCA
  • GAU, GAC, GAA
  • AGU, AGC, AGA
  • GUU, GUC, GUA
The codon on mRNA are CAU-CCU-AAA-CUG. 
Identify the correct sequence of amino acid  
  • $$His-Pro-Lys-Leu$$
  • $$Pro-His-Lys-Leu$$
  • $$His-Pro-Leu-Lys$$
  • $$Pro-Leu-Lys-His$$
Select the wrong statement.
  • The human genome contains $$3164.7$$ million nucleotide bases
  • Less than $$10\%$$ of the genome codes for protein
  • Repeated sequences make up very large portion of the human genome
  • Chromosome $$1$$ has most genes $$(2968)$$ and Y has the fewest $$(231)$$
The genetic code of proline are?
  • CCC CCG CCU
  • CUU UCA CUG
  • GUU GUC GUG
  • GGU GUC GGA
Expressed Sequence Tags (ESTs) refers to?
  • Genes expressed as RNA
  • Polypeptide expression
  • DNA polymorphism
  • Novel DNA sequences
Name the enzyme that facilitates opening of DNA helix during transcription.
  • DNA helicase
  • DNA polymerase
  • RNA polymerase
  • DNA ligase
Which of the following statements explains DNA as the preferred hereditary material, in comparison to RNA?
i. RNA has a 2-OH group at every nucleotide which makes it highly reactive.
ii. DNA is double stranded hence is neither reactive nor labile.
iii. DNA can readily undergo mutation resulting in faster evolution and adaptability.
iv. DNA can catalyse various physiological reactions.
  • i and ii
  • iii and iv
  • i and iii
  • ii and iv
The characteristics of a molecular probe are
(I) Very long molecule
(II) Double stranded
(III) DNA or RNA
(IV) Complementary to a part of desired gene
The correct options are
  • I, II
  • II, III
  • III, IV
  • IV, I
Match the following and choose the correct combination from the options given.

Column-IColumn-II
A.Walter Sutton1.Discovered penicillin
B.Thomas Hunt Morgan2.Discovered the chromosomal basis of heredity
C.James Watson3.Described the phenomenon of linkage and crossing over
D.Alexander Fleming4.Discovered the double helical structure of DNA
  • A- 1, B- 4, C- 2, D- 3
  • A- 2, B- 3, C- 1, D- 4
  • A- 3, B- 2, C- 1, D- 4
  • A- 2, B- 3, C- 4, D- 1
  • A- 4, B- 1, C- 2, D- 3
Feulgen staining is a special technique for the identification of 
  • RNA
  • DNA
  • Protein
  • Carbohydrate
Which enzyme initiates the synthesis of DNA template strand?
  • RNA polymerase
  • DNA polymerase
  • DNA ligase
  • None of the above
"It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for genetic material" - This is written by
  • Meselson and Stahl
  • Archibold Garrod
  • Severo Ochoa
  • Watson and Crick
The enzyme which can cut molecules of DNA into segments is known as
  • DNA polymerase
  • DNA ligase
  • Restriction enzyme
  • DNA gyrase
What is antisense technology?
  • When a piece of RNA that is complementary in sequence is used to stop expression of a specific gene
  • RNA polymerase producing DNA
  • A cell displaying a foreign antigen used for synthesis of antigens
  • Production of somaclonal variants in tissue cultures
In a given DNA segment, the number of nucleotides of guanine is 75 and those of thymine isWhat will be the total number of nucleotides in the segment?
  • 75
  • 750
  • 225
  • 300
If there are 120 adenine molecules in a B-DNA double helical structure showing 20 coils, what is the number of pyrimidine nucleotides forming three hydrogen bonds in it?
  • 80
  • 100
  • 120
  • 140
Which enzyme catalyzes the separation of DNA strands during DNA replication?
  • DNA polymerase
  • Helicase
  • Ligase
  • Topoisomerase
If percentage of cytosine is 18%, what will be the percentage of adenine?
  • 32%
  • 64%
  • 36%
  • 23%
The double helical model of the DNA was proposed by Watson and Crick based on that what data produced by Wilkins and Franklin?
  • Hybridization
  • DNA sequencing
  • Southern blotting
  • X-ray diffraction
  • Both A and D
Which of the following codons has no tRNA?
  • UAA
  • UAU
  • UGU
  • UGC
  • UGG
Which of the following is not relevant to the structure of double helical DNA?
  • The helix makes one complete spiral turn every 34A$$^o$$.
  • The diameter of the helix is 20A$$^o$$.
  • The distance between adjacent nucleotide is 3.4A$$^o$$.
  • Each strand of helix has a backbone made up of alternating ribose sugar and phosphate.
  • The two adjacent sugar molecules joined with phosphate by phosphodiester bond.

Which one of the following group of codons is called as degenerate codons?
  • UAA, UAG and UGA
  • GUA, GUG, GCA and GCG 
  • UUC, UUG, CCU, CAA and CUG
  • UUA and UUG, CUU, CUC and CUG
  • AAC, AAG, GAC and CGG
Whose experiments cracked the DNA and discovered unequivocally that a genetic code is a "triplet"?
  • Nirenberg and Matthaei
  • Hershey and Chase
  • Morgan and Sturtevant
  • Beadle and Tatum
Which one of the following is correct?
  • Introns are present in mRNA and exons are present in tRNA.
  • Codons are present in mRNA and anticodons in tRNA.
  • Every intron is a set of three terminator codons.
  • Exons are present in eukaryotes while introns are present in prokaryotes.
Which one of the following pairs of codons are correctly matched with their function or the signal for the particular amino acid?
  • AUG, ACG : Start/Methionine
  • UUA, UCA : Leucine
  • GUU, GCU : Alanine
  • UAG, UGA : Stop
Identify the correct and incorrect statements.
A.  The four nucleotide bases are not necessarily present in DNA in exact equal proportions.
B.  The total amount of purines are equal to the total amount of pyrimidines.
C.  DNA ligase enzyme act to hydrolyse or breakdown a polynucleotide chain into its component nucleotides.
D. Nuclease enzymes are capable of restoring an intact DNA duplex.
  • B is correct but A, C and D are wrong.
  • A and B are wrong but C and D are correct.
  • A, B and C are correct but D is wrong.
  • A and B are correct but C and D are wrong.
  • B, C and D are correct but A is wrong.
The base sequence for a nucleic acid segment is given CAG, AGG, CGA, CCA. From this, it can definitely be concluded that it is a segment of which strand?
  • DNA strand
  • mRNA strand
  • tRNA strand
  • Data not sufficient
What is a triplet codon?
  • Fixed
  • Degenerate
  • Ambiguous
  • Non-wobbly
How many effective codons are there for the synthesis of twenty amino acids?
  • 64
  • 32
  • 60
  • 61

A naturally occurring coding strand composed of alternating C and U residues would result in the formation of
  • A polypeptide containing alternating leu and ser residues
  • A polypeptide containing either leu or ser residues
  • A polypeptide containing only leu residues
  • A polypeptide containing only ser residues
  • A polypeptide containing only phe residues
What is the number of stop codons which do not code for any amino acid?
  • 1
  • 2
  • 3
  • 4
Which of the following group of codons code for amino acid serine?
  • CUU, CUC, CUA and CUG
  • UAU, UAC, UGU and UGC
  • UCU, UCC, UCA and UCG
  • UGU, UGC, UGA and UAG
  • GUU, GUC, GCU and GCC
Which conserved motifs are found in E.coli genes?
  • TATA box
  • CAAT box
  • Pribnow box
  • All of the above
Identify the correct match between the codons and coding functions.

Column I                        Column II

A. AUG                               Phenylalanine

B. UAA                               Methionine

C. UUU                                Tryptophan

D. UGG                               Termination
  • A- 1, B- 4, C- 2, D- 3
  • A- 2, B- 4, C- 1, D- 3
  • A- 4, B- 3, C- 2, D- 1
  • A- 4, B- 1, C- 3, D- 2
  • A- 2, B- 3, C- 4, D- 1
Given below is a sample of a portion of DNA strand giving the base sequence on the opposite strands. What is so special shown in it?
5' _______ GAATTC _______    3'
3'_______  CTTAAG  _______   5'
  • Palindromic sequence of base pairs
  • Replication completed
  • Deletion mutation
  • Start codon at the 5' end

Select the incorrect statement(s).

Six codons do not code for any amino acid.

Codon is read in mRNA in a contiguous fashion.

Three codons function as stop codons.

The initiator codon AUG codes for methionine .
  • 1, 2 and 4 are incorrect.
  • 1, 2 and 3 are incorrect.
  • 2, 3 and 4 are incorrect.
  • 2 alone is incorrect.
  • 1 is incorrect.
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