The diagram of a nucleosome is shown above.
(i) Identify the parts labeUed a, b, c and d in it.
(ii) Name the positively-charged and negatively charged components in it.

Given above is the electron micrograph (EM) picture of 'beads-on-string'.
a) What do the 'beads' represent?
(b) What do they constitute in a eukaryotic nucleus? When does its maximum condensation occur in a ceU?
(c) What is the function of non-histone chromosomal proteins in the nucleus?

The Central dogma of molecular biology is shown above.
(a) Who proposed this?
(b) Identify the processes A, Band C in the above representation.
(c) Why is it not applicable to certain viruses?

A DNA replication fork is shown above. Answer the following questions based on that.
(a) Identity the polarity of the strands a - b and c-d.
(b) Name the enzyme that catalyses the process.
(c) What are the newly synthesised strands A - B and C - D known as?

A DNA replication fork is shown above. Answer the following questions based on that.
(i) Why does DNA replication occur in such small forks?
(ii) What is a synthesis and b synthesis?
(iii) Mention the polarity at A and B.

A complete transcription unit is given above.
(a) Identify A, B, C and D in the figure.
(b) Name the enzyme that catalyses this process.

A particular stage in the transcription of a bacterium is given above. Answer the following questions:
(a) Name the stage in the process.
(b) Identify A, B, C, D and E in the diagram.

A stage in the process of transcription in a prokaryote is shown above.
(a) Name the stage in transcription.
(b) Identify A and B in the diagram.
(c) Can this process be coupled to translation ? Justify your answer.

Given below is a sequence of steps in the transcription in a eukaryotic cell.

(a) Fill in the blanks 1, 2, 3 and 4.
(b) Why is splicing necessary?

A hypothetical mRNA with 12 codons is shown above.
(a) How many amino acids will be coded by this? Justify your answer.
(b) Mention the dual functions of the codon, AUG.

Read the sequence of nucleotides in the given segment of mRNA and the sequence of amino acids in the polypeptide translated by it.

Polypeptide: Met - Phe - Met - Pro - Val - Ser.
(a) Write the sequence of nucleotides in the template strand of DNA, along with its polarity, from which this mRNA has been transcribed.
(b) If the three bases (shown by the arrow) are deleted, what will be the amino acid sequence in the new polypeptide chain?
(c) What does the last codon (X) of this mRNA stand for?

A small stretch of DNA that codes for a polypeptide is given below:
3' ... CAT CAT AGA TGAAAC ... 5'
(a) Which type of mutation could have occurred in each type resulting in the following mistakes during replication of the above original sequence?

(b) How many amino acids will be translated in each of the above two cases?

Study the following carefully and explain why mutation (A) did not cause any sickle cell anaemia inspite of change in the molecular structure of the gene which codes for Haemoglobin, whereas a similar mutation (B) did.
(The question is based on properties of the genetic code. c = codon, a = amino acid, Hb = Haemoglobin).

Given above are four amino acyl-tRNAs with their anticodons.
(a) Name the process by which the tRNA binds to the amino acid. Which end of the tRNA is the amino acid bound to?
(b) Find the sequence oftheir binding to the mRNA transcribed by a template strand of DNA having the base sequence as follows:
3' TAC CGT GAC GTC 5'.
(c) Write the sequence of bases on the mRNA transcribed.

Lac operon in the 'switched on' position is shown above.
(a) Identify the molecule A and the enzymes B, C and D in the diagram.
(b) When will this operon get 'switched off'?