Unit3 Study Guide

Unit3 Study Guide - 1. Describe the structure of DNA...

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1. Describe the structure of DNA including the following: - the structure of a DNA nucleotide: DNA nucleotide is made of phosphate, sugar, and nitrogenous base. - the names of the 4 nitrogenous bases found in DNA: There are adenine, guanine; purines and thymine and cytosine; pyrimidines. - the arrangements of nucleotides in a DNA molecule: One DNA molecule is made of 2 very long chains of nucleotides. Each chain is a string of nucleotides joined by sugar-phosphate covalent bonds. (Stable arrangements) Nitrogenous bases are hydrophobic and stick inwards. (Stick in the middle – Van der Wall forced stabilized) Chains loosely bonded to each other by hydrogen bonds. - purines (double-ring structure), pymidines (single-ring structure) - complementary base paring: A with T, and C with G. - the location and importance of hydrogen bonds: Chains are loosely bonded to each other by hydrogen bonds. (Stick in the middle – Van der Walls forced stabilized) A forms 2 hydrogen bonds with T. C forms 3 hydrogen bonds with G. 2. Describe the basic process of DNA replication. Include: idea of templates, importance of complementary base pairing, functions of DNA polymerase. - Each strand of original molecule acts as a template of a new complementary strand. DNA polymerase: enzyme that builds new strands of DNA by “reading” old strand (parental DNA temple strand) using complementary base pairing rules.
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3. Describe the initial events of DNA replication including the functions of orgins of replication, helicase, and single-stranded binding proteins. First, helicase attach to “orgin of replications” and untwist the DNA and break some hydrogen bonds. Then, single-stranded binding proteins keep DNA open because proteins have shapes. 4. DNA replication is complicated by the anti-parallel nature of the DNA molecule. Explain the roles of Okazaki fragments and DNA ligase in replication. Okazaki fragments: A short segment of DNA synthesized on a template strand during DNA replication. Many Okazaki fragments make up the lagging strand of newly synthesized DNA. DNA ligase: A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3’ end of a new DNA fragment to the 5’ end of a growing chain. Okazaki fragments are joined by DNA ligase.
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5. Explain why DNA replication requires primase and RNA primers. Primase can start an RNA chain from scratch. Primase joins RNA nucleotides together one at a time, making a primer complementary to the template strand at the location where initiation of the new DNA strand will occur. 6. Describe the methods and results of each of these experiments. Explain clearly how the results provided evidence that DNA was the genetic material. - nuclear transplantation experiments
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This note was uploaded on 04/21/2008 for the course BIOL 400 taught by Professor Scott during the Spring '08 term at Los Rios Colleges.

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Unit3 Study Guide - 1. Describe the structure of DNA...

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