AIPMT Molecular Biology Higher Order Thinking Skills

1. The DNA fingerprinting analysis of four family members is shown below.

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2. Given the diagram of the lac operon showing an operon of inducible enzymes. Identify components and enzymes (A, B, C, D and E).

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(a) A-P-Galactosidase, B-Permease, C-Transacetylase, D-Repressor protein, E-Inducer (lactose)
(b) A-P Galactosidase, B-Permease, C-Transacetylase, D-Inducer (lactose), E-Repressor protein
(c) A-p Galactosidase, B-Transacetylase, C-Permease, D-Repressor protein, E-Inducer (lactose)
(d) A-Permease, B-Transacetylase, C-p Galactosidase, D-Repressor protein, E-Inducer (lactose)
3. 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?
(a) Only when both lactose and glucose are absent.
(b) Only when both lactose and glucose are present.
(c) Only when lactose is absent and glucose is present.
(d) Only when lactose is present and glucose is absent.
4. A mRNA with 6 codons (for chain initiation, termination and amino acid) is included in the rectangle shown in the given figure. The different types of mutations, indicated as A, B, C and D are respectively

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(a) silent, mis-sense, non-sense and frameshift
(b) silent, mis-sense, frameshift and non-sense
(c) mis-sense, silent, non-sense and frameshift
(d) mis-sense, silent, frameshift and non-sense

5. Hershey and Chase’s work in 1952 is summarised in the drawing given below. Study it and mark the most important feature of this work.

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(a) Tj particles were grown for the first time on E. coli.
(b) Radioactive isotopes were used in this biological experiments.
(c) Protein coat showed high level of S35.
(d) It was the phage DNA and not protein which entered the bacterial cell and gave rise to number of phage progeny.
6. 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.
7. In the given DNA segment ATG ACC AGG ACC CCA ACA, the first base, gets mutated on the left side. The effect of this on coding by this DNA segment will result in
(a) complete change in the type as well as sequence of amino acids
(b) change in one amino acid only
(c) no change in the sequence
(d) one amino acid less in the protein.
8. Study the given figure and identify A to F.

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(a) A-Variable arm, B-DHU-loop, C-TΨC-loop, D-Anticodon arm, E-codon, F-Variable arm
(b) A-Amino acid arm, B-TΨC-loop, C-Variable arm, D-Anticodon arm, E-codon, F- DHU-loop
(c) A-Amino acid arm, B-TΨC-loop, C-Anticodon loop, D-Anticodon, E-codon, F- DHU-loop
(d) A-Amino acid arm, B—TΨC-loop, C-Anticodon loop, D-Anticodon, E-codon, F- Variable arm
9. Identify ‘X’ in the following diagram of lac operon transcription.

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(a) Activator protein (b) Allolactose
(c) Galactose (d) Tryptophan
10. A sequence of the picture of polypeptide synthesis shows a ribosome holding two transfer RNAs. One fRNA has a polypeptide chain attached to it and the other fRNA has a single amino acid attached to it. What should be the next step?
(a) The polypeptide chain moves over and bonds to the single amino acid.
(b) The fRNA with amino acids leaves the ribosome.
(c) The amino acid moves over and bonds to the polypeptide chain.
(d) The fRNA with the polypeptide chain leaves the ribosome
11. In eukaryotes, the process of processing of primary transcript involves
(a) removal of introns
(b) capping at 5’end
(c) tailing (polyadenylation) at 3′ end
(d) all of these.
12. 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.

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13. Some data is given below regarding DNA and mRNA

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Which DNA serves as DNA template for mRNA?
(a) DNA strand 1
(b) DNA strand 1 and 2
(c) Neither strand 1 nor 2
(d) DNA strand 2
14. If the gene has sequence AAATGCGCGATA, the m-RNA formed against it and the sequence of bases in corresponding anticodon will be
(a) UUUACGCGCUAU and AAAUGCGCGAUA
(b) UAUCGCGCAUUU andAUAGCGCGUAAA
(c) UUUACCTUGUAU andAAAUGGUACAUA
(d) UAUGUTCCAUUU and AUACAUGGUAAA.
15. 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?
(a) Polyploidy
(b) Chromosomal mutation
(c) Non-coding DNA
(d) Coding DNA

Answers

1. (c) 2. (a) 3. (d) 4. (d) 5. (d) 6. (b) 7. (b) 8. (c)
9.(b) 10. (a) 11. (d) 12. (c) 13. (a)14. (a)15. (c)

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