BIO130H1 Study Guide - Midterm Guide: Histone Octamer, Dna Supercoil, Top1
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BIO130H1 Full Course Notes
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Document Summary
Histones: histone octamer core composed of 2x(h2a, h2b, h3, h4), positively-charged to interact with. Histones have amino terminal tails that control dna replication and transcription. Cohesin: looped domains of dna wrap around this to form protein scaffolds. Condensin: facilitates condensing of chromosomes, especially during mitosis. Primase: lays down rna primers, thus providing 3" -oh for formation of new strand. Ligase: catalyzes 5"-3" phophodiester bonds between adjacent nucleotides. Dna polymerase: lays down nucleotides during dna replication. Also used to fill gap after exonuclease and endonuclease remove mismatched bases. Single-strand binding proteins: bind to single strands of dna to keep bubble open during dna replication. Topoisomerase i: only breaks one strand of dna for tension relief. Topoisomerase ii: breaks both strands for dna, often to allow another dna helix to pass through it. Telomerase: in eukaryotes, elongates 3" overhangs to allow dnap to complementarily lengthen the shortened 5" end.
