Class 12 Molecular Basis of Inheritance worksheet

Sample questions

Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.

Section A · multiple choice

1. 1.

   The double-helix model of DNA was proposed by:

   1. Griffith
   2. Hershey and Chase
   3. Meselson and Stahl
   4. Watson and Crick (1953)

   Answer

   (d) Watson and Crick (1953)

2. 2.

   The template strand of a gene reads 5′-TCATTTGCCCAT-3′. The mRNA transcribed from this gene reads:

   1. 5′-AUGGGCAAAUGA-3′
   2. 5′-UACCCGUUUACU-3′
   3. 5′-ATGGGCAAATGA-3′
   4. 5′-AGUAAACGGGUA-3′

   Answer

   (a) 5′-AUGGGCAAAUGA-3′

   the mRNA is complementary to the template strand and runs antiparallel to it

3. 3.

   The mRNA 5′-AUGUUUAAGUAA-3′ is translated. The polypeptide formed is:

   1. Met–Phe–Lys–Stop
   2. Lys–Phe–Met
   3. Phe–Lys
   4. Met–Phe–Lys

   Answer

   (d) Met–Phe–Lys

   AUG Met, UUU Phe, AAG Lys, UAA stop

Section B · short answer

1. 4.

   What is the central dogma of molecular biology?

   Answer

   Genetic information flows from DNA to RNA (transcription) and from RNA to protein (translation). In some viruses information flows from RNA to DNA (reverse transcription).

2. 5.

   Translate the mRNA 5′-UAUGAUUCGAUCCCGUGGCUGA-3′. How many amino acids does the polypeptide have?

   Answer

   Met–Ile–Arg–Ser–Arg–Gly; 6 amino acids

   start at AUG, read in triplets, stop at UGA

Section C · long answer

1. 6.

   Describe the double-helix model of DNA.

   Answer

   Two polynucleotide chains wind round each other in a right-handed helix with the sugar–phosphate backbone outside and bases inside. The chains are antiparallel (5′ → 3′ and 3′ → 5′). Bases pair by hydrogen bonds: A with T (two bonds) and G with C (three), so a purine always faces a pyrimidine and the width is uniform. The pitch is 3.4 nm with about 10 base pairs per turn, 0.34 nm apart.

Fresh sheets for your child

In the app, every Molecular Basis of Inheritance sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.

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