BIO207H5 Chapter Notes -Metaphase, Mitosis, Chromatin
Document Summary
Organisms contain genetic material that governs an individual"s characteristics and that is transferred from parent to progeny. Deoxyribonucleic acid (dna) is the genetic material of all living organisms and some viruses. Ribonucleic acid (rna) is the genetic material only of certain viruses. In prokaryote and eukaryotes, the dna is always double-stranded, whereas in viruses the genetic material may be double-or single stranded dna or rna, depending on the virus. Dna and rna are macromolecules composed of smaller building blocks called nucleotides. Each nucleotide consists of a five-carbon sugar (deoxyribose in dna, ribose in rna) to which are attached a nitrogenous base and a phosphate group. In dna, the 4 possible bases are adenine, guanine, cytosine, and thymine; in rna, the four possible bases are adenine, guanine, cytosine, and uracil. According to watson and crick"s model, the dna molecule consists of two polynucleotide (polymers of nucleotides) chains joined by hydrogen bonds between pairs of bases: adenine (a) and thymine (t),