Question

In the DNA molecule,

• A. The proportion of adenine in relation to thymine varies with the organism.
• B. There are two strands which run antiparallel one in $5^{\prime }\to 3^{\prime }$ direction and other in $3^{\prime }\to 5^{\prime }$.
• C. The total amount of purine nucleotides and pyrimidine nucleotides is not always equal.
• D. There are two strands which run parallel in the $5^{\prime }\to 3^{\prime }$ direction.

Answer 1

The correct option is B There are two strands which run antiparallel one in $5^{\prime }\to 3^{\prime }$ direction and other in $3^{\prime }\to 5^{\prime }$.

DNA (Deoxyribonucleic Acid) is composed of two polynucleotide strands (the polymers of nucleotides), which form what looks like a ladder. The nitrogenous bases in DNA store the instructions for making polypeptide chains, essentially coding for every feature of the entire organism. The two polynucleotide strands run 'antiparallel' to each other, with nitrogenous bases projecting inwards. The term 'antiparallel' means that the strands run in opposite directions, parallel to one another. The antiparallel strands twist in a complete DNA structure, forming a double helix.