Chapter 7: DNA Structure and Replication

1. Why was DNA found to be the hereditary molecule of life? 2. DNA replication mechanism – remember synthesis of leading and lagging strand and how they differ and how they are similar 3. The players involved in DNA replication 4. The concept of Hershey-Chase experiment 5. Methods of molecular genetics analysis and how we make use of DNA replication process 6. Dideoxynucleotide DNA sequencing is a method for discovering the sequence of a DNA fragment – very basic concept was discussed but the idea of what “players” or substrates are needed to replicate DNA

How many bonds between G and C?

3

How many bonds between A and T?

2

What direction does DNA go in?

5’ → 3’

What gives DNA the directionally?

the orientation of the phosphate bond

DNA topoisomerase

words at the region ahead of the replication fork to prevent supercoiling

Helicase (DnaB)

Unwinds the double helix

SSB

Coats the DNA around the replication fork to prevent rewinding of the DNA

Primase

synthesizes RNA primers

• Manufactures a 10-12 base segment of RNA

DNA pol III

extends the primers, adding on to the 3' end, to make the bulk of the new DNA. This is the most important enzyme for DNA replication.

• replication, proofreading and editing

• 3’ → 5’

DNA pol I

Removes and replaces RNA primer with DNA

• filling if gap after removal RNA primer, DNA repair, removal of RNA primers

• moves both ways

replisomes

the enzymes and proteins involved area parts of large complex aggregations of proteins and enzymes

What is a Nucleotide?

Adenosine triphosphate, Adenosine diphosphate, adenosine monophosphate

What is a Nucleoside?

Adenosine

What is the name of the bond that joins one nucleotide to another in the DNA strand?

Phosphodiester bond

Is the Phosphodiester bond a covalent or a non covalent bond?

Covalent

Which chemical groups of nucleotides react to form the phosphodiester bond?

formation between alpha phosphate of the incoming nucleotide triphosphate and the 3’ hydroxyl group of the last nucleotide added to the strand.

What bond joins one strand of DNA to the other strand?

Hydrogen bonds

What is DNA replication?

Semiconservative

What forms the lagging strand?

Okazaki fragments

Replication in prokaryotes differs from replication in eukaryotes for which of these reasons?

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many

What would be the effects on DNA replication of mutation of DNA pol III caused it to lose each of the following activities: 5’ to 3’ polymerase activity

There would be a loss of the ability to synthesize DNA by adding nucleotide

What would be the effects on DNA replication of mutation of DNA pol III caused it to lose each of the following activities: 3’ to 5’ exonuclease activity

proofread newly synthesized DNA and correct errors in replication as they occur