Chromosomes • Chromosomes are rod-shaped structures made of DNA & Proteins. • Histones: DNA wraps around these proteins, they help maintain the shape of the chromosome and aid in tight packing of DNA
Chromatids • Chromosomes consist of two identical halves, each called a chromatid • Chromatids form as the DNA makes a copy of itself before cell division. • Chromatids attach at centromere, which holds them together until cell division. • Chromatin: less tightly coiled DNA-protein complex
Prokaryotic v Eukaryotic • Prokaryotes usually only have DNA with one chromosome, which is attached to the inside of cell membrane • Prokaryotes have circular DNA molecule • Both are very compact
Chromosomes or Autosomes • Sex Chromosomes: determine sex of organism, carry genes for other characteristics. Either X or Y. • Autosomes: all the other chromosomes • Do you know how many chromosomes humans have? How many are sex chromosomes, how many autosomes?
Homologous Chromosomes • Two copies of each autosome • Same size and shape and carry same genes • Ex: eye color