Exam 2 Study Guide

Exam 2 Study Guide - Exam 2 Study Guide DNA 1 A nitrogenous base which can be either adenine guanine cytosine or thymine(in the case of RNA thymine

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Exam 2 Study Guide DNA 1. A nitrogenous base, which can be either adenine, guanine, cytosine, or thymine (in the case of RNA, thymine is replaced by uracil). 1. Purine—A,G, 2. Pyrmidine—C,T 2. A five-carbon sugar, called deoxyribose because it is lacking an oxygen group on one of its carbons. 3. One or more phosphate groups. 4. anti-parallel pairing, 1. the nitrogen base groups face the inside of the helix while the sugar and phosphate groups face outward. 2. The sugar and phosphate groups in the helix therefore make up the phosphate backbone of DNA. 3. The backbone is highly negatively charged as a result of the phosphate groups. Double Helix o an anti-parallel, o right-handed, o helical periodicity of 3.4 nanometers o 10 repeating units per helical turn. o B DNA thought to be biologically relevant form; 10.5 bp/turn o A DNA 11 bp per turn; similar to structure of dsRNA and RNA-DNA duplexes o Z DNA left-handed helix with zig-zap pattern A common in low humidity and in RNA Base Pairs o A=T make 2 hydrogen bonds o G=C make 3 hydrogen bonds RNA 1. RNA is a single-stranded nucleic acid. 2. RNA has a ribose sugar instead of a deoxyribose sugar like DNA.
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1. Addition of hydroxyl group at 2’ position 3. RNA nucleotides have a uracil base instead of thymine. DNA Replication Semi-conservative o If the original DNA helix is called the "parental" DNA, the two resulting helices can be called "daughter" helices. o Each of these two daughter helices is a nearly exact copy of the parental helix o Each newly synthesized strand of DNA (daughter strand) is made by the addition of a nucleotide that is complementary to the parent strand of DNA. o In this way, DNA replication is semi-conservative, meaning that one parent strand is always passed on to the daughter helix of DNA. Separation o DNA Helicase untwists the helix at locations called replication origins. Polymerization o one strand is oriented in the 5' to 3' direction while the other strand is oriented in the 3' to 5' direction. o the enzyme that carries out the replication, DNA polymerase III , only functions in the 5' to 3' direction. o one adding nucleotides one by one in the direction of the replication fork Leading the nucleotides are added in the 5' to 3' direction. Triggered by RNA primase , which adds the first nucleotide to the nascent chain the DNA polymerase simply sits near the replication fork, moving as the fork does, adding nucleotides one after the other, preserving the proper anti-parallel orientation continous o the other able to add nucleotides only in chunks (Okazaki) lagging the enzyme must move away from the fork On the lagging strand, then, an enzyme called primase that moves with the replication fork synthesizes numerous RNA primers, each of which triggers the growth of an Okazaki fragment. The RNA primers are eventually removed leaving gaps that are
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This note was uploaded on 07/17/2011 for the course BIO 151 taught by Professor Grinblat during the Summer '08 term at Wisconsin.

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Exam 2 Study Guide - Exam 2 Study Guide DNA 1 A nitrogenous base which can be either adenine guanine cytosine or thymine(in the case of RNA thymine

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