Molecular Basis of Inheritance: Class 12 Previous Year Questions

Molecular Basis of Inheritance questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. _________ Page 21 of 24 { } 31. (a) Trace the events from fertilization till implantation of blastocyst in human female. Also mention the site where fertilization takes place. 5 OR (b) (i) Case studies of some couples are given below. They were not able to hav…
   Board 20265 markscase-based
2. (a) (i) Watson and Crick’s discovery of double helical structure was based on which two findings. Also mention the name of the scientists associated with these findings. 2 (ii) Write down the salient features of double helix structure of DNA (any three points)…
   Board 20265 markslong answer
3. _________ Page 21 of 24 { } 32. (a) Observe the segment of mRNA given below and answers the questions given below : (i) Explain and illustrate the steps involved to make fully processed hn RNA. 3 (ii) Gene encoding RNA polymerase I and RNA polymerase III have …
   Board 20265 markslong answer
4. (a) The diagram below shows the sequence of amino acids in part of haemoglobin molecule. (i) If the base *T is substituted with A, in ‘C*TT’ of DNA strand how would it affect the haemoglobin chain ? 1 (ii) Name the condition and the effects associated with the…
   Board 20262 marksshort answer
5. Assertion (A) : DNA Ligase is used to join DNA fragments. 1 Reason (R) : It catalyses the formation of glycosidic bonds between nucleotides.
   Board 20261 markAssertion-Reason
6. Observe the given picture carefully. A mixture of DNA with fragments ranging from 100 base pairs to 1800 base pairs were separated by electrophoresis on agarose gel with the following arrangement : (a) What result will be obtained in staining with ethidium bro…
   Board 20263 marksshort answer
7. (a) What is a genetic code ? 1 (b) Why did scientists feel the need to propose a genetic code ? 1 (c) Genetic code is said to be ‘Universal’. Why ?
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8. How do scientists use microinjection and gene gun in biotechnology ?
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9. Which of the following statements about plasmids is incorrect ? 1 (A) Plasmids have the ability to replicate within the bacterial cell. (B) Their replication is controlled by chromosomal DNA. (C) They are autonomously replicating circular extra-chromosomal DNA…
   Board 20261 markMCQ
10. _________ Page 3 of 24 { } 1. To separate repetitive DNA from bulk genomic DNA, which of the following method is used ? 1 (A) Elution (B) Southern Blotting (C) Polymerase Chain Reaction (D) Density Gradient Centrifugation _________ Page 4 of 24 { } 2. …
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11. A bacterium having radioactive thymidine in its DNA is allowed to multiply in a medium having non-radioactive thymidine for two generations. What percentage of bacteria will have radioactive thymidine in its DNA ? 1 (A) 100 (B) 50 (C) 75 (D) 25
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12. The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine. Study the complete tra…
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13. Assertion (A) : One of the property of genetic code is degeneracy. Reason (R) : Some amino acids can be coded by more than one codon.
    Board 20251 markAssertion-Reason
14. Study the items of Column-I and those of Column-II : Column-I Column-I RNA polymerase I (i) (a) 18s rRNA (b) RNA polymerase II (ii) SnRNAs (c) RNA polymerase III (ii) hnRNA Choose the option that correctly matches the items of Column-I with those of Column-II …
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15. Study the diagram given below and answer the questions that follows : (a) Identify the structure shown in the above figure. (b) Identify the labels P and Q. (c) Write the nature of histone proteins. (d) Distinguish between Euchromatin and Heterochromatin. 15 /…
    Board 20253 marksshort answer
16. Explain the basis on which gel electrophoresis technique works. Write any two ways the products obtained through this technique can be utilised.
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17. Amplification of gene of interest by using DNA polymerase may go upto (A) 0.1 million times (B)1 million times 1 billion times (C) (D)1 trillion times 7IPage 9. 5AATGCTAGGCAC3 (A)5'-UUACGAACCGAG - 3' (B)5'-AAUGCUAGGCAC- 3' (C) 5'- UUACGUACCGUG - 3' (D) 5'- AAC…
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18. The sequence of nitrogenous bases in a segment of a coding strand of DNA is 5' - AATGCTAGGCAC - 3'. Choose the option that shows the correct sequence of nitrogenous bases in the mRNA transcribed by the DNA. (A)5'-UUACGAACCGAG -3' (B) 5'- AAUGCUAGGCAC- 3' (C) 5…
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19. RNA interference (RNAi) helps in making tobacco-plant resistant to a nematode (Meloidegyne incognitia) Choose the correct option that shows how RNAi is achieved : (A) Preventing the process of translation of mRNA of the nematode. (B) Preventing the process of …
    Board 20251 markAssertion-Reason
20. Given below is a heterogeneous RNA formed during Eukaryotic transcription : How many introns and exons respectively are present in the hnRNA ? (A) 7, 7 (B) 8, 7 (C) 8, 8 (D) 7, 8 7IPage 8. I- 3TR -1 (a) (i) 18s 3R3R (rRNA) (b) (ii) H 3 (SnRNAs) 3 -III (c) (ii)…
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