DNA Chromosomes DNA is a type of organic

DNA & Chromosomes § DNA is a type of organic macromolecule called Deoxyribonucleic Acid § DNA is made up of repeating monomers called Nucleotides § DNA has a distinct shape called a Double Helix § Segments of DNA that code for traits (eye color, etc) are Genes

DNA & Chromosomes § DNA is wrapped up with proteins (histones) to form chromatin and chromosomes • • Chromatin is DNA and histone loosely coiled together Chromosomes are DNA and histone coiled very tightly together § Chromosomes appear as a “fat X” shape § Each side or half of a chromosome is called a chromatid § Both chromatids are held together by a centromere

Sexual Reproduction § Half of the chromosomes come from the mother; half from the father § § Sex Chromosomes determine the sex of the organism (X & Y) All other chromosomes are called Autosomes § Autosomes come in pairs (1 from mother; 1 from father) • The pairs that are the same size, shape, and types of genes are called Homologous Pairs (Homologues) Ex: 1 chromosome has gene for hair color and 1 comes from EACH parent. They have same trait type, but not the same information (brown vs blonde)

DNA & Chromosomes § Sex chromosomes have different genes on them and have different sizes, so they can not be homologous § Cells having 2 sets of chromosomes are called Diploid (2 n) • § Humans (46); Fruit Fly (8); Plum (48); Adders Tongue Fern (1262) Cells that come from sexually reproduced organisms that have only 1 set of chromosomes are called Haploid (1 n) • These are the sex cells (egg and sperm)