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NEET UG Unit 6A: DNA and RNA Structure & Replication — practice questions

Explore 26 free Unit 6A: DNA and RNA Structure & Replication questions in NEET UG Biology. Open each question or exercise to read its content, reference answers and available explanation.

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Unit 6A: DNA and RNA Structure & Replication questions and exercises with answers

Showing questions 1–26 of 26.

Who proposed the double-helix model of DNA in 1953 using X-ray diffraction data from Wilkins and Franklin?Read the answer and worked solution →In a DNA double helix, adenine pairs with thymine through how many hydrogen bonds?Read the answer and worked solution →Which scientist first identified DNA in 1869 and named the acidic nuclear substance 'Nuclein'?Read the answer and worked solution →The Human Genome Project was completed in which year?Read the answer and worked solution →In the lac operon, the i gene codes for which protein?Read the answer and worked solution →Which of the following is a stop codon?Read the answer and worked solution →In the Hershey-Chase experiment, radioactive sulfur (35S) was used to specifically label which component of the bacteriophage?Read the answer and worked solution →A nucleosome in eukaryotic chromatin contains how many base pairs of DNA wrapped around the histone octamer?Read the answer and worked solution →Which enzyme joins the discontinuously synthesised Okazaki fragments on the lagging strand?Read the answer and worked solution →In eukaryotes, which RNA polymerase transcribes the precursor of mRNA (hnRNA)?Read the answer and worked solution →Which feature of the genetic code allows the same amino acid to be specified by more than one codon?Read the answer and worked solution →In bacterial ribosomes, peptide bond formation is catalysed by which molecule?Read the answer and worked solution →In Griffith's transformation experiment with Streptococcus pneumoniae, mice died when injected with which combination?Read the answer and worked solution →If the pitch of the DNA helix is 3.4 nm and there are 10 base pairs per turn, the rise per base pair is:Read the answer and worked solution →E. coli completes replication of its 4.6 x 10^6 bp genome in 18 minutes. The average polymerisation rate is closest to:Read the answer and worked solution →In a transcription unit, the strand that has the polarity 3' to 5' and is used by RNA polymerase to direct RNA synthesis is called the:Read the answer and worked solution →A double-stranded DNA contains 20% cytosine. What percentage of adenine is present?Read the answer and worked solution →If the coding strand of a transcription unit reads 5'-ATGCATGCATGC-3', the mRNA transcribed will be:Read the answer and worked solution →The true intracellular inducer of the lac operon is:Read the answer and worked solution →Insertion of two extra bases in the middle of a structural gene most likely produces:Read the answer and worked solution →Which RNA polymerase in eukaryotes transcribes 5S rRNA, tRNA and snRNAs?Read the answer and worked solution →Which chromosome carries the largest number of genes and which carries the fewest, according to HGP?Read the answer and worked solution →Sickle-cell anemia is caused by a point mutation in the beta-globin gene that substitutes:Read the answer and worked solution →DNA fingerprinting developed by Alec Jeffreys originally used which type of repetitive sequence as a probe?Read the answer and worked solution →Which step is NOT part of the classical DNA-fingerprinting workflow as described in your syllabus?Read the answer and worked solution →In bacterial transcription the sigma factor associates with RNA polymerase to:Read the answer and worked solution →

Worked practice questions

Who proposed the double-helix model of DNA in 1953 using X-ray diffraction data from Wilkins and Franklin?

  1. Watson and Crick
  2. Avery and MacLeod
  3. Hershey and Chase
  4. Meselson and Stahl
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Correct answer: A. Watson and Crick

Watson and Crick proposed the double-helix model in 1953, building on X-ray diffraction images produced by Maurice Wilkins and Rosalind Franklin and on Chargaff's base-ratio rule.

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In a DNA double helix, adenine pairs with thymine through how many hydrogen bonds?

  1. Two
  2. Three
  3. One
  4. Four
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Correct answer: A. Two

A pairs with T via 2 hydrogen bonds G pairs with C via 3. This A=T, G=C rule reflects Chargaff's equivalence and gives a near-constant inter-strand distance.

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Which scientist first identified DNA in 1869 and named the acidic nuclear substance 'Nuclein'?

  1. Frederick Griffith
  2. Erwin Chargaff
  3. Alec Jeffreys
  4. Friedrich Meischer
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Correct answer: D. Friedrich Meischer

Friedrich Meischer isolated an acidic nuclear substance in 1869 and called it 'Nuclein'. Its long polymeric nature delayed structural elucidation until 1953.

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