ANAT 9999 Lecture 4: Chapter 4 Notes
Document Summary
Cytosine and thymine are pyrimidines (single carbon-nitrogen ring) Adenine and guanine are purines (double rings) Chromatin is a mix of dna and histone (protein) and in most cells, occurs as 46 chromosomes. Nucleosome is histone and dna wrapped around it. When dna is about to divide, it duplicates all its dna; each chromosome now consists of sister chromatids joined together by the centromere, which has a protein called a kinetochore on each side. A gene is an information-containing segment of dna that codes for the production of an rna molecule. All the dna, coding and noncoding in one 23-chromosome set is called the genome. A single gene can code for many different proteins. Various combinations of single-nucleotide polymorphisms is what gives variation. The genetic code is a system that enables 4 nucleotides to code for the amino acid sequences of all proteins. A sequence of 3 dna nucleotides that stands for 1 amino acid is called a base triplet.