Chromosomes

Chromosomes are composed of 2 identical halves, each of these halves are called **chromatids**. The point which connects the 2 chromatids together is called the **centromere**. DNA is not tightly coiled into chromosomes except during cell division. in humans these are pairs 1 – 22 Humans have 46 chromosomes which are in 23 pairs. Every somatic cell in the human body has the diploid number of chromosomes (2N) which is 46, the human gametes contain the haploid number of chromosomes (1N) which is 23. The reason for this??? When a sperm (1N) combines with an egg (1N) you end up with a (2N) zygote. [|Chromosome Video]
 * Chromosome ** – rod shaped structure of tightly coiled DNA and histones.
 * DNA ** – Deoxyribose Nucleic Acid – Contains all information necessary for cell functions, the blue-print for life.
 * Autosomes **– All body chromosomes
 * Sex chromosomes ** – in humans these are pair 23
 * Homologous chromosomes ** – homologues – each pair of chromosomes – are the same size and shape and carry genes for the same traits.
 * <span style="font-family: Arial,sans-serif;">Karyotype **<span style="font-family: Arial,sans-serif;"> –picture of the chromosomes of a cell – shows the homologous chromosomes.
 * <span style="font-family: Arial,sans-serif;">Diploid **<span style="font-family: Arial,sans-serif;"> – 2N – contain both chromosomes of a homologous pair – in humans the diploid number is 46.
 * <span style="font-family: Arial,sans-serif;">Haploid **<span style="font-family: Arial,sans-serif;"> – 1N – contains only one chromosome from each homologous pair – in humans the haploid number is 23.
 * <span style="font-family: Arial,sans-serif;">Somatic cells **<span style="font-family: Arial,sans-serif;"> – Body cells – all cells in the body except for the gametes.
 * <span style="font-family: Arial,sans-serif;">Gametes **<span style="font-family: Arial,sans-serif;"> – Sex cells – females have eggs and males have sperm.