Question

Describe Watson and Crick model of DNA.

Answer 1

A double-stranded, antiparallel, right-handed helix is the structure of DNA, as represented in the model of Watson and Crick. The DNA strands' sugar-phosphate backbones make up the outside of the helix. On the inside, the nitrogenous bases are established and form hydrogen-bonded pairs that keep together the DNA strands.

Complete answer:
• DNA stands for Deoxyribonucleic acid, a molecule containing the instructions required to grow, live and reproduce an organism.
• It is a form of nucleic acid and is one of the four main types of macromolecules considered to be important to all life forms.
• DNA's three-dimensional structure, first suggested in $1953$ by James D. Watson and Francis H. C. Crick, consists of two long helical strands that are coiled to form a double helix around a central axis.
• Two polymer strands coiled around each other are used in each DNA molecule.
• Each strand has a $5'$end (with a group of phosphate) and a $3'$ end (with a hydroxyl group).
• The strands are antiparallel, meaning one strand runs in a direction from $5'$ to $3'$ , while the other strand runs in a direction from $3'$ to $5'$ .
• The diameter of the double helix is $2nm$ , and at an interval of $3.4nm$ , the double helical structure repeats, corresponding to ten base pairs.

Note: If an A on one strand is detected, it must be combined with a T on the other (and vice versa). Similarly, for a partner on the opposite strand, a G located on one strand must always have a C. These associations of A-T and G-C are known as complementary base pairs. Since a large purine (A or G) is often combined with a small pyrimidine (T or C), the helix's diameter is uniform, reaching approximately $222$ nanometers.