1. Genes & Chromosomes Chromosomes - single large DNA molecule and its associated proteins, containing many genes; stores & transmits genetic info Gene - a chromosomal segment that codes for a single functional polypeptide chain or RNA molecule Genome - all of cell’s genes + intergenic DNA (<10% of genome is genes) chromatin (2 chromatids)

2. Genes & Chromosomes Genomes Species/VirusGenome size HIV9000 bases Bacteriophage 48,500 bp Flu virus1.8 million bp Bacteria (prok)4.6 million bp Yeast (euk)15 million bp C. elegans (worm, euk))97 million bp Human (euk)3 billion bp

3. Genes & Chromosomes Introns & Exons Eukaryotic genes have many intervening sequences between gene sequences gene sequences intervening sequences

4. Genes & Chromosomes Size of genome vs. size of cell

5. Genes & Chromosomes Compaction of DNA

6. Genes & Chromosomes Compaction of DNA Beads-on-a-string Protein (histones, basic) + DNA (acidic) = Nucleosome

7. Beads on a String (in Colorado)

8. Genes & Chromosomes Compaction of DNA Beads-on-a-string

9. Genes & Chromosomes Compaction of DNA Supercoiling Relaxed

10. Genes & Chromosomes Compaction of DNA Important for DNA packaging, DNA replication Topoisomerases can underwind and/or relax DNA