CHM 4220 EXAM 2 (Exam Questions & Answers) A+

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CHM 4220 EXAM 2 (Exam Questions & Answers) A+, 1. What are the two major conditions for genetic information being accurately copied every time a cell divides? 1. it has to be extremely accurate. 2. i... t has to take place at a high speed. 2. What were 3 models of DNA replication proposed and which one was confirmed valid? 1. conservative replication model 2. dispersive replication model 3. semiconservative replication model semiconservative replication model was confirmed valid. . How Meselson and Stahl proved correct DNA replication model? they used two nitrogen isotopes, grew E. coli in 15N media first, then moved to 14N media. Cultured E.coli were subjected to equilibrium density gradient centrifugation 3. What is replicon and the major characteristics of 3 modes of DNA replication? Replicon is a segment of DNA that undergoes replication. Each replicon contains an origin of replication. Theta Replication, Rolling Circle Replication and Linear Eukaryotic Replication Theta: Double-stranded DNA unwinds at the replication origin producing single-starnded templates for the synthesis of new DNA. A replication bubble forms, usually with a replication fork at each end. The forks proceed around the circle. Eventually 2 circular DNA molecules are produced. Rolling Circle: (virus/ F factor) Replication is initiated by a break in one of the nucleotides strands. DNA synthesis begins at the 3” end of the broken strand, the inner strand is used as a template. The 5” end of the broken strand is displaced. Cleavage releases a single-stranded linear DNA and a double-stranded circular DNA. The linear DNA may circularize and serve as a template for synthesis of a complementary strand. The product is one circular molecule and one linear molecule that may circulize. Linear Eukaryotic: Each chromosome contains numerous origins. At each origin the DNA unwind, producing a replication bubble. DNA synthesis takes place on both strands at each end of the bubble as the replication forks proceed outward. Eventually, the forks of adjacent bubbles run into each other and the segments of DNA fuse, producing two identical linear DNA molecules. . How would you define the major difference between theta and rolling circle replication? Theta creates a bubble; it can be either bi or unidirectional. Rolling circle is only unidirectional and is replicated by peeling off a strand of DNA during its replication. . Is linear replication bidirectional or unidirectional? Explain. Bidirectional because it has multiple replicons, multiple origins of replication. 4) What are the requirements for DNA replication? A template strand, Raw material: nucleotides, Enzymes and other proteins. . What serve as template? DNA is a double helix. So, during replication it unwinds and separates into 2 strands. 1 strand will be called the non- coding and the other will be called the coding strand. The non-coding strand will be the template 3’ to 5’for the new one. [Show More]

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