BOLOGY 107 1st Edition Lecture 26 Outline of Last Lecture I Corrections to Notes on X linked Gene Pedigree II Non Mendelian Genetics a Maternal imprinting b Genetic Material c DNA structure Outline of Current Lecture III DNA Structure a Watson and Crick b Genetic Material c DNA Replication Current Lecture DNA Structure 1 Watson and Crick a Known i A T and G C form hydrogen bonds Chargaff ii Total strand diameter Franklin b Discovered i DNA is a right handed helix ii Strands are anti parallel 1 3 and 5 prime ends are on the opposite sides of each other iii Bases are on the inside phosphates and sugars are on the outside iv C G and A T pairs are from opposite strands 1 The pairs are what hold the strands together v 10 5 bases per full turn c Implications i Linear order of four possible options each provides extreme amount of information storage ii Double strand allows for template to make replicas also helpful for damage repair 2 Genetic material a DNA in each cell is about 2 meters long i Must be compacted to about 10 m These 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 again c During interphase DNA is still highly organized just not compacted 3 DNA replication a Three modes were hypothesized i Conservative a full copy is made the original strand is still intact ii Semi conservative strands are separated new complimentary strand made each new strand has half of the original iii Dispersive strands are separated into chunks part of the original is in every copy after multiple rounds of replication b Tested by using heavy nitrogen to form DNA allowed to replicate with normal nitrogen i Centrifuged by weight ii Results concluded the semi conservative model c How DNA replicates i Form replication bubble ii In bacteria replication forks start in one spot split in both directions until they meet up 1 Each side is replicated iii In eukaryotes replication is started in many places move bi directionally iv 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 bonds
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