LIFE SCIENCE

Detailed explanation-1: -X-ray crystallography can be used to see the nucleotide arrangement in DNA. It is an experimental science that can determine the atomic and molecular structure of a crystal by a beam of incident X-ray. The beam passes through the crystalline structure and gets diffracted into many specific directions.

Detailed explanation-2: -Created by Rosalind Franklin using a technique called X-ray crystallography, it revealed the helical shape of the DNA molecule. Watson and Crick realized that DNA was made up of two chains of nucleotide pairs that encode the genetic information for all living things.

Detailed explanation-3: -Nucleotides are arranged in two long strands that form a spiral called a double helix.

Detailed explanation-4: -Nucleosides are -N-g1ycosides formed between a purine or pyrimidine and a carbohydrate, almost always either -D-ribofuranose or 2-deoxy--D-ribose (Figure 30.3). The numbering systems for the purine and pyrimidines of nucleosides follow the conventions of the bases.