Practice Test

Q1) Which of the following pairs is incorrectly matched? Show Answer

Q2) If a double stranded DNA has 20% of cytosine, what will be the percentage of adenine in it? Show Answer

Q3) Histone proteins are Show Answer

Q4) If the sequence of bases in one strand of DNA is ATGCATGCA what would be the sequence of bases on complementary strand? Show Answer

Q5) RNA is the genetic material in Show Answer

Q6) Synthesis of DNA from RNA is explained by Show Answer

Q7) Read the following statements and select the correct option.
(i) Loosely packed and lightly stained region of chromatin is called as heterochromatin.
(ii) Densely packed and dark stained region of chromatin is called as euchromatin.
(iii) A typical nucleosome contains 200 bp of DNA helix. Show Answer

Q8) Chemically, RNA is (i) reactive and (ii) stable as compared to DNA. Show Answer

Q9) How far is each base pair from the next one in DNA double helix model? Show Answer

Q10) Which of the following shows the correct positions of the phosphate (P), sugar (S) and base (B) molecules in the line diagrams representing structure of DNA? Show Answer

Q11) In a DNA molecule the phosphate group is attached to carbon ________ of the sugar residue of its own nucleotide and carbon ________ of the sugar residue of the next nucleotide by _______ bonds. Show Answer

Q12) DNA as an acidic substance present in nucleus was first identified by ________ in 1869; he named it as ________. Show Answer

Q13) Find out the wrong sentence about heterochromatin. Show Answer

Q14) In one polynucleotide strand of a DNA molecule the ratio of A + T/G + C is 0.3. What is the A + G/T + C ratio of the entire DNA molecule? Show Answer

Q15) The structures in chromatin seen as 'beads-on-string' when viewed under electron microscope are called Show Answer

Q16) The year 2003 was celebrated as the 50th anniversary of discovery of Show Answer

Q17) Which of the following phenomena was experimentally proved by Meselson and Stahl? Show Answer

Q18) To prove that DNA is the genetic material, which radioactive isotopes were used by Hershey and Chase (1952) in their experiments? Show Answer

Q19) Watson and Crick (1953) proposed DNA double helix model and won the nobel Prize; their model of DNA was based on
(i) X-ray diffraction studies of DNA done by Wilkins and Franklin.
(ii) Chargaff's base equivalence rule.
(iii) Griffith's transformation experiment.
(iv) Messelson and Stahl's experiment. Show Answer

Q20) The process of transformation is not affected by which of the following enzymes?
A. Dnase
B. Rnase
C. Peptidase
D. Lipase Show Answer

Q21) Which of the following criteria should be fulfilled by a molecule to act as a genetic material?
(i) It should be able to replicate.
(ii) It should be structurally and chemically stable.
(iii) It should be able to undergo slow mutations.
(iv) It should be able to express itself in the form of 'Mendelian characters'. Show Answer

Q22) Select the right statement out of the following.
(i) Both DNA and RNA are able to mutate.
(ii) RNA being unstable, mutates at a faster rate.
(iii) RNA shows catalytic properties.
(iv) Presence of uracil (U) at place of thymine (T) confers additional stability to RNA. Show Answer

Q23) First experimental proof for semi-conservative DNA replication was shown in Show Answer

Q24) DNA replication takes place at _________ phase of the cell cycle. Show Answer

Q25) Select the incorrect statement regarding DNA replication. Show Answer

Q26) Select the correct match of enzyme with its related function. Show Answer

Q27) Other than DNA polymerase, which are the enzymes involved in DNA synthesis? Show Answer

Q28) Which of the following figures correctly represents the replication fork formed during DNA replication? Show Answer

Q29) During transcription the site of DNA molecule at which RNA polymerase binds is called Show Answer

Q30) If the sequence of bases in DNA is GCTTAGGCAA then the sequence of bases in its transcript will be Show Answer

Q31) Methyl guanosine triphosphate is added to the 5 end of hnRNA in a process of Show Answer

Q32) In transcription in eukaryotes, heterogenous nuclear RNA (hnRNA) is transcribed by Show Answer

Q33) The structural genes, in eukaryotes, possess coding and non-coding sequences called as (i) and (ii) respectively. Show Answer

Q34) If the sequence of bases in coding strand of DNA is ATTCGATG, then the sequence of bases in mRNA will be Show Answer

Q35) Polycistronic messenger RNA (mRNA) usually occurs in Show Answer

Q36) In an animal cell, the processes of transcription and translation occur in Show Answer

Q37) In eukaryotes, the process of processing of primary transcript involves Show Answer

Q38) The process of copying genetic information from one strand of DNA to RNA is termed as _______. Show Answer

Q39) What would be the base sequence of RNA transcript obtained from the given DNA segment? 5' - G C A T T C G G C T A G T A A C - 3' Coding strand of DNA 3' - C G T A A G C C G A T C A T T G - 5' Non-coding strand of DNA Show Answer

Q40) Transcription unit Show Answer

Q41) The fully processed hnRNA is called as (i) and is transported out of the (ii) into the (iii) for translation. Show Answer

Q42) Select the incorrectly matched pair. Show Answer

Q43) Which out of the following statements is incorrect? Show Answer

Q44) The enzymes DNA dependent RNA polymerase catalyses the polymerization reaction in __________ direction. Show Answer

Q45) Some amino acids are coded by more than one codon, hence the genetic code is Show Answer

Q46) The mutations that involve addition, deletion or substitution of a single base pair in a gene are referred to as Show Answer

Q47) Sickle cell anaemia results from a single base substitution in a gene, thus it is an example of Show Answer

Q48) The three codons which result in the termination of polypeptide chain synthesis are Show Answer

Q49) Amino acids which are specified by single codons are Show Answer

Q50) Read the following statements.
(i) One codon codes for only one amino acid.
(ii) Some amino acids are coded by more than one codon.
(iii) The sequence of triplet nitrogenous bases in DNA or mRNA corresponds to the amino acid sequence in the polypeptide chain.
Give suitable terms for the characteristics of 'genetic code' as per the above statements. Show Answer

Q51) What would happen if in a gene encoding a polypeptide of 50 amino acids, 25th codon (UAU) is mutated to UAA? Show Answer

Q52) Amino acid acceptor end of tRNA lies at Show Answer

Q53) During translation, activated amino acids get linked to tRNA. This process is commonly called as Show Answer

Q54) Which RNA carries the amino acids from the amino acid pool to mRNA during protein synthesis? Show Answer

Q55) Nucleotide sequence of the DNA strand from which this mRNA was transcribed is Show Answer

Q56) Which codons respectively code for proline and valine amino acids in the given polypeptide chain, respectively? Show Answer

Q57) In a mRNA molecule, untranslated regions (UTRs) are present at Show Answer

Q58) UTRs are the untranslated regions present on Show Answer

Q59) The differences between mRNA and tRNA are that
(i) mRNA has more elaborated 3-dimensional structure due to extensive base-pairing.
(ii) tRNA has more elaborated 3-dimensional structure due to extensive base-pairing.
(iii) tRNA is usually smaller than mRNA.
(iv) mRNA bears anticodon but tRNA has codons. Show Answer

Q60) During expression of an operon, RNA polymerase binds to Show Answer

Q61) Repressible operon system is usually found in (i) pathways. The pathway's end product serves as a (ii) to activate the repressor, turn off enzyme synthesis and prevent overproduction of the end product of the pathway. Genes for this operon are usually switched (iii) and the repressor is synthesized in an (iv) form. Show Answer

Q62) Inducible operon system usually occurs in (i) pathways. Nutrient molecules serve as (ii) to stimulate production of the enzymes necessary for their breakdown. Genes for inducible operon are usually switched (iii) and the repressor is synthesized in an (iv) form. Show Answer

Q63) Regulation of gene expression occurs at the level of Show Answer

Q64) The sequence of structural genes in lac operon is Show Answer

Q65) Human genome consists of approximately Show Answer

Q66) Estimated number of genes in human beings is Show Answer

Q67) Which of the following statements regarding 'human genome' is incorrect? Show Answer

Q68) Arrange the various steps of DNA fingerprinting technique in the correct order.
(i) Separation of DNA fragments by electrophoresis.
(ii) Digestion of DNA by restriction endonucleases.
(iii) Hybridization using labelled VNTR probe.
(iv) Isolation of DNA.
(v) Detection of hybridized DNA fragments by auto radiography.
(vi) Transferring the separated DNA fragments to nitrocellulose membrane. Show Answer

Q69) C-value is the characteristic DNA content in a haploid cell of a given species. Earlier it was considered that C-value correlates with organism complexity. However, it is now evident that C-value varies enormously among species and that this bears no correlation with the complexity of the organisms. For example, the cells of some salamanders may contain 40 times more DNA than those of humans. Which of the following explains this C-value paradox? Show Answer

Q70) An organism uses 20 amino acids while its DNA is made up of 6 types of nitrogenous bases. What would be the minimum size of a codon? Show Answer

Q71) You have created a fusion between trp operon and lac operon which encodes the enzymes for tryptophan biosynthesis, under the regulatory control of the lac operator. Under which of the following conditions will tryptophan synthase be induced in the strain that carries the chimeric operator fused operons? Show Answer

Q72) In a DNA strand the nucleotides are linked together by Show Answer

Q73) A nucleoside differs from a nucleotide. It lacks the Show Answer

Q74) Both deoxyribose and ribose belong to a class of sugars called Show Answer

Q75) The fact that a purine base always paired through hydrogen bonds with a pyrimidine base leads to, in the DNA double helix Show Answer

Q76) The net electric charge on DNA and histones is Show Answer

Q77) The promoter site and the terminator site for transcription are located at Show Answer

Q78) Which of the following statements is the most appropriate for sickle cell anaemia? Show Answer

Q79) One of the following is true with respect to AUG Show Answer

Q80) The first genetic material could be Show Answer

Q81) With regard to mature mRNA in eukaryotes Show Answer

Q82) The human chromosome with the highest and least number of genes in them are respectively Show Answer

Q83) Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA? Show Answer

Q84) 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? Show Answer

Q85) Discontinuous synthesis of DNA occurs in one strand, because Show Answer

Q86) Which of the following steps in transcription is catalyzed by RNA polymerase? Show Answer

Q87) Control of gene expression takes place at the level of Show Answer

Q88) Regulatory proteins are the accessory proteins that interact with RNA polymerase and affect its role in transcription. Which of the following statements is correct about regulatory protein? Show Answer

Q89) Which was the last human chromosome to be completely sequenced? Show Answer

Q90) Which of the following are the functions of RNA? Show Answer

Q91) 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 Show Answer

Q92) In some viruses, DNA is synthesised by using RNA as template. Such a DNA is called Show Answer

Q93) 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 Show Answer

Q94) The RNA polymerase holoenzyme transcribes Show Answer

Q95) If the base sequence of a codon in mRNA is 5' - AUG - 3', the sequence of tRNA pairing with it must be Show Answer

Q96) The amino acid attaches to the tRNA at its Show Answer

Q97) To initiate translation, the mRNA first binds to Show Answer

Q98) In E. coli, the lac operon gets switched on when Show Answer

Q99) Assertion: The sugar phosphate backbone of two chains in DNA double helix show anti-parallel polarity.
Reason: The phosphodiester bonds in one strand go from a 3' carbon of one nucleotide to a 5' carbon of adjacent nucleotide, whereas those in complementary strand go vice versa. Show Answer

Q100) Assertion: In Griffith's experiment, a mixture of heat-killed virulent bacteria R and live non-virulent bacteria S, lead to the death of mice.
Reason: 'Transforming principle' got transferred from heat killed R strain to S strain and made it virulent. Show Answer

Q101) Assertion: DNA is considered to be better genetic material than RNA for most organisms.
Reason: 2' - OH group present in DNA makes it labile and less reactive. Show Answer

Q102) Assertion: The mechanism of DNA replication is semiconservative in nature.
Reason: Each of the complementary strands of the parental double helix is conserved during the process. Show Answer

Q103) Assertion: Eukaryotic mRNA requires post-transcription processing for formation of functional mRNA.
Reason: Eukaryotic transcripts possess extra non-functional segments called introns. Show Answer

Q104) Assertion: A change in nitrogen base at the third position of a codon causes change in the expression of the codon.
Reason: A codon is mostly read by all the three nitrogen bases. Show Answer

Q105) Assertion: Untranslated regions are sequences of RNA before initiation codon and after termination codon.
Reason: Untranslated regions provide stability to mRNA and also increase transnational efficiency. Show Answer

Q106) Assertion: The predominant site for control of gene expression in prokaryotes is transcription initiation.
Reason: The activity of RNA polymerase is regulated by accessory proteins, which affect recognition of start sites. Show Answer

Q107) Assertion: Repetitive sequences make up very large portion of human genome.
Reason: Repetitive sequences do not have direct coding in functions in the genome. Show Answer

Q108) Assertion: When the DNA sequences of two people are cut using the same restriction enzyme, the length and number of fragments obtained are different for both.
Reason: DNA sequence is arranged tandemly in many copy numbers which varies from chromosome to chromosome in an individual, showing high degree of polymorphism. Show Answer

Q109) Assertion: Polycistronic mRNA, found in prokaryotes, specify a number of polypeptides.
Reason: Monocistronic mRNA, found in eukaryotes, specify only a single polypeptide. Show Answer

Q110) Assertion: tRNA recongnises its corresponding codon in mRNA.
Reason: For each codon, there is an individual tRNA. Show Answer

Q111) Assertion: Lac operon is a repressible operon.
Reason: The product of gene activity stops the activity of the said gene. Show Answer