Base pairs bond when three hydrogen bonds form between guanine and cytosine. Two hydrogen bonds form between adenine and thymine or adenine and uracil. Complementary pairs always involve one purine and one pyrimidine base
Chromosoms are threadlike structures of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. Humans normally have 23 chromosomes.
Karyotypes are the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
DNA replication occurs in two steps. First, an initiator protein unwinds a short stretch of the DNA double helix. Then, a protein known as helicase attaches to and breaks apart the hydrogen bonds between the bases on the DNA strands, pulling apart the two strands.
THE DAMAGING OF DNA