LIFE 120 Midterm: EXAM 3 PREP
Document Summary
Telo(cid:373)eres resol(cid:448)e the (cid:862)e(cid:374)d repli(cid:272)atio(cid:374)(cid:863) pro(cid:271)le(cid:373: telomeres repetitive non-coding sequences at ends of eukaryotic chromosomes. Added by telomerase; active only in germ cells. Chromosome dna shortens when it replicates but does not lose coding sequence. Telomerase is active in some cancer cells! A chromosome consists of a dna molecule packed together with proteins. Bacterial chromosome: circular dsdna molecule associated with a small amount of protein, dna is (cid:862)super(cid:272)oiled(cid:863), fou(cid:374)d i(cid:374) the nucleoid. Eukaryotic chromosome linear dsdna molecules associated with a large amount of protein: chromatin - dna/ protein complex found in the nucleus of eukaryotic cells. Histones small positively charged proteins that wrap up the dsdna helix (h2a, h2b, Nucleosome complex of dna wrapped around 2 molecules of each of 4 main histones with tails out. H1 histone helps condense nucleosomes into 30nm chromatin fibers. Highly compacted dna that is not readily expressed: euchromatin loosely packed dna with highly expressed genes.
