Genetics

Chromatin: Types of chromatin Chromatin In non-dividing cells, the DNA exists as chromatin and appears uncoiled and randomly dispersed After DNA replication (S phase) the chromatin begins to condense in preparation for mitosis Chromatin consists of 50% DNA, 50% proteins, mainly histones Chromatin is the structure that the eukaryotic genome is packaged into It allows long molecules of DNA to fit into the small volume of the nucleus The basic structural unit of chromatin is the nucleosome Further folding and compaction of chromatin produces visible metaphase chromosomes during cell division Heterochromatin vs Euchromatin Euchromation Active Chromatin The majority of chromatin is this form Less condensed, lightly packed in the nucleus (basic ?beads on a string? form ?check)

The Hardy-Weinberg principle The Hardy-Weinberg principle: the frequency of alleles and genotypes in a population?s gene pool will remain constant from one generation to the next. Provided that only Mendelian segregation and recombination of alleles are at work Describes a population that is not evolving The Hardy-Weinberg principle describes a hypothetical population Changes to allelic frequency and genotype always occur in real populations The equation p2 + 2pq + q2 = 1 p2 and q2 represent the frequencies of the homozygous genotypes 2pq represents the frequency of the heterozygous genotype Conditions of the Hardy-Weinberg Principle Population size = extremely large No gene flow can occur (no immigration or emigration of individuals) No mutations No natural selection