The number of DNA molecules in each chromosome is

The correct answer is one.

• A single chromosome contains only one DNA (deoxyribonucleic acid) molecule and so many genes.
• Humans have 23 pairs of chromosomes.
  • 22 pairs of autosomes chromosomes and one pair of sex chromosomes, X and Y.

Important Points

• In the cell nucleus, the DNA molecule is packaged into thread-like structures called chromosomes.
  • A chromosome (microscopic structure) is made up of DNA tightly coiled many times around proteins called histones that support its structure.
  • A chromosome has two arm - p arm (short arm) and q arm (long arm), joined in the location of the centromere.

Key Points

• The information in DNA (double helix structure) is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
  • DNA has two base pairs, A-T and G-C, attached to a sugar-phosphate backbone.