Read the following and answer any four questions from (i) to (v) given below:
The process of translation requires transfer of genetic information from a polymer of nucleotides to synthesise a polymer of amino acids. The relationship between the sequence of amino acids in a polypeptide and nucleotide sequence of DNA or mRNA is called genetic code. George Gamow suggested that in order to code for all the 20 amino acids, code should be made up of three nucleotides.
(i) What is a codon?

(a) A length of DNA which codes for a particular protein	(b) A part of the tRNA molecule to which a specific amino acid is attached.
(c) A part of the tRNA molecule which recognises the triplet code on the messenger RNA.	(d) A part of the messenger RNA molecule that has a sequence of bases coding for an amino acid.

(ii) Three consecutive bases in the DNA molecule provide the code for each amino acid in a protein molecule. What is the maximum number of different triplets that could occurs ?

(a) 16

(b) 20

(c) 24

(d) 64

(iii) Listed below are some amino acids and their corresponding mRNA triplets.

Amino acid	mRNA triplet
Phenylalanine	UUU
Lysine	AAG
Arginine	CGA
Alanine	GCA

Which DNA sequence would be needed to produce the following polypeptide sequence? Alanine- Arginine- Lysine- Phenylalanine

(a) CGT GCT TTC AAA

(b) CGT GCT TTC TTT

(c) CGU GCU UUC AAA

(d) CGU GCU UUC TTT

(iv) Identify the non-sense codons among the following.

(a) AUG

(b) GUG

(c) UAA

(d) UGG

(v) A polypeptide is made using synthetic mRNA molecules as shown.

Synthetic mRNA used	Polypeptide produced
UUUAAAUUUAAA	Phenylalanine-lysine- phenylalanine-lysine

What are the DNA codes for the amino acids phenylalanine and lysine?

Phenylalanine	Lysine
(a) AAA	TTT
(b) AAA	UUU
(c) GGG	CCC
(d) TTT	GGG

Read the following and answer any four questions from (i) to (v) given below:
In prokaryotes, DNA is circular and present in the cytoplasm but in eukaryotes, DNA is linear and mainly confined to the nucleus. DNA or deoxyribonucleic acid is a long polymer of nucleotides. In 1953, the first correct double helical structure of DNA was worked out by Watson and Crick. Based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin. It is composed of three components, i.e., A phosphate group, a deoxyribose sugar and a nitrogenous base. Different forms of DNA are B-DNA, Z-DNA, A-DNA, C-DNA and D-DNA.
(i) Name the linkage present between the nitrogen base and pentose sugar in DNA.

(a) Phosphodiester bond

(b) Glycosidic bond

(c) Hydrogen bond

(d) None of these

(ii) The double helix structure of DNA was proposed by

(a) James Watson and Francis Crick

(b) Earwin Chargaff

(c) Federick Griffith

(d) Hershey and Chase

(iii) The double chain of B-DNA is coiled in a helical fashion. The spiral twisting of B-DNA duplex produces

(a) right and left part

(b) major and minor grooves

(c) upper and lower sides

(d) linear and circular part.

(iv) Assertion: The two strands of DNA helix have uniform distance between them.
Reason: A large sized purine always paired opposite to a small sized pyrimidine.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.	(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.	(d) Both assertion and reason are false.

 (v) Which of the following describes the structure of B-DNA?

Polynucleotide chains	Number of base pairs per complete turn of helix
(a) Parallel	5
(b) Anti-parallel	10
(c) Parallel	15
(d) Anti-parallel	20

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.

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.