BOLOGY 107 1st Edition Lecture 26Outline of Last Lecture I. Corrections to Notes on X-linked Gene PedigreeII. Non-Mendelian Geneticsa. Maternal imprintingb. Genetic Materialc. DNA structureOutline of Current Lecture III. DNA Structurea. Watson and Crickb. Genetic Materialc. DNA ReplicationCurrent LectureDNA Structure1) Watson and Cricka) Knowni) A-T and G-C form hydrogen bonds (Chargaff)ii) Total strand diameter (Franklin)b) Discovered i) DNA is a right-handed helixii) Strands are anti-parallel(1) 3’ and 5’ prime ends are on the opposite sides of each otheriii) Bases are on the inside, phosphates and sugars are on the outsideiv) C-G and A-T pairs are from opposite strands(1) The pairs are what hold the strands togetherv) 10.5 bases per full turnc) Implications i) Linear order of four possible options each provides extreme amount of information storageii) Double strand allows for template to make replicas, also helpful for damage repair2) Genetic materiala) DNA in each cell is about 2 meters longi) Must be compacted to about 10 μmThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b) Chromosomes i) DNA is compacted for mitosis(1) DNA is wrapped around histones(2) Histones are stacked, then looped, then looped againc) During interphase, DNA is still highly organized, just not compacted3) DNA replicationa) Three modes were hypothesizedi) Conservative- a full copy is made, the original strand is still intactii) Semi-conservative- strands are separated, new complimentary strand made, each new strand has half of the originaliii) Dispersive- strands are separated into chunks, part of the original is in every copy after multiple rounds of replicationb) Tested by using heavy nitrogen to form DNA, allowed to replicate with normal nitrogeni) Centrifuged by weightii) Results concluded the semi-conservative modelc) How DNA replicatesi) Form replication bubbleii) In bacteria, replication forks start in one spot, split in both directions until they meet up(1) Each side is replicatediii) In eukaryotes, replication is started in many places, move bi-directionallyiv) Proteins involved:(1) Helicase- separates the strands(2) Single-strand binding protein- prevents re-binding of the strands(3) Topoisomerase- relaxes “supercoiling” that builds up ahead of helicase(4) Polymerases- attach new bases to form complimentary strands(a) Only build in a 5’ to 3’ direction(b) Sample nucleotides until the proper one hydrogen
View Full Document
Unlocking...