Which of the following is not consistent with the base pairings in a double stranded DNA molecule?

1. The number of C equals the number of G

2. The number of A equals the number of T

3. The amount of purine is equal to the amount of pyrimidines

4. The ratio of (G+C) to (A+T) is same for each species

Which of the following is not a feature of the double helix model of DNA ?

(1) The two chains have anti-parallel polarity

(2) A purine always comes opposite to a pyrimidine

(3) The pitch of the DNA is 3.4 nm

(4) The two chains are coiled in a left handed fashion

In the DNA molecule

(1) the total amount of purine nucleotides and pyrimidine nucleotides is not always equal

(2) there are two strands, which run parallel in the 5’ → 3’direction

(3) the proportion of adenine in relation to thymine varies with the organism

(4) there are two strands, which run antiparallel-one in 5’ → 3’ direction and other in 3’ → 5’

The two polynucleotide chains in DNA are:

(1) parallel

(2) discontinuous

(3) antiparallel

(4) semiconservative

One turn of the helix in a B-form DNA is approximately:

(1) 20 nm

(2) 0.34 nm

(3) 3.4 nm

(4) 2 nm