Genetics

DNA, Chromsomes and Genes

DNA wraps itself around chromosomal proteins to form chromosomes, and genes are composed of DNA which reside at different locations along the chromosome.
Every three leters (bases) makes up a codon, which codes for a protein or gene. A change in the sequence of DNA is a mutation, and it can be deadly, affect one or more traits, or sometimes have no effect at all. Due to a mutation, a protein is missing, and it causes Cystic Fibrosis.
Chromosomes are structures of DNA and proteins found in every cell. There are 23 pairs, or 46 total, chromosomes in each cell, and an individual gets them from his or her parents.

Meiosis

Because there are two cell divisions during meiosis, there will always be 4 haploid daughter cells. Gametes/sex cells undergo meosis. During prophase of meiosis I, there are 46 chromosomes, but after the Xs separate to different cells, there are only 23. There will still be 23 chromomes for the remainder of meiosis II, but the Xs are just splitting apart. During crossing over, the chromosomes switch genetic material, so there are new allele combinations. If meiosis goes wrong a mutation can occur, or the homologs will not separate correctly (nonsidjunction). If nondisjunction occurs, the cells will have an unequal amount of chromosomes.

Mitosis

During mitosis, the single stranded chromosomes double to form x chromosomes. Because there is only one division, the x's separate, and there is still 46 single stranded chromomes. Somatic cells divide by mitosis. When mitosis goes wrong, mutations can occur causing genetic disorders, and it can also cause cancer.