Genes & ChromosomesChromosomes - single large DNA molecule and its associated proteins, containing many genes; stores & transmits genetic infoGene - a chromosomal segment that codes for a single functional polypeptide chain or RNA moleculeGenome - all of cell’s genes + intergenic DNA (<10% of genome is genes)

chromatin (2 chromatids)

Genes & ChromosomesGenomes

Species/Virus Genome size

HIV 9000 basesBacteriophage 48,500 bpFlu virus 1.8 million bpBacteria (prok) 4.6 million bpYeast (euk) 15 million bpC. elegans (worm, euk)) 97 million bpHuman (euk) 3 billion bp

Genes & ChromosomesIntrons & ExonsEukaryotic genes have many intervening sequences between gene sequences

gene sequencesintervening sequences

Genes & Chromosomes

Size of genome vs. size of cell

Genes & ChromosomesCompaction of DNA

Genes & Chromosomes

Compaction of DNABeads-on-a-stringProtein (histones, basic) + DNA (acidic) = Nucleosome

Beads on a String(in Colorado)

Genes & ChromosomesCompaction of DNABeads-on-a-string

Genes & ChromosomesCompaction of DNASupercoiling

Relaxed

Genes & Chromosomes

Compaction of DNAImportant for DNA packaging, DNA replicationTopoisomerases can underwind and/or relax DNA