Lecture 9 - DNA Replication

Who was Friedrich Meischer?

Discovered nuclein in white blood cells

Who was Frederick Griffith?

R bacteria transformed into virulent S bacteria

Who was Alfred Hershey and Martha Chase?

Used bacteriophages to confirm DNA is genetic material

Who was Erwin Chargaff?

Determined specific base-pairing rules

Who was Rosalind Franklin and Maurice Wilkens?

Discovered DNA is a double helix

Who was James Watson and Francis Crick?

Proposed the overall model of DNA

What are nucleotides composed of?

Deoxyribose - 5 carbon sugar, phosphate group, and nitrogenous bases

What are the features of DNA?

Sugar-phosphate backbone on the outside, nitrogen bases on the inside, and anti-parallel strands are held together by hydrogen bonding

What are the base pairing rules?

A pairs with T, making 2 hydrogen bonds. C pairs with G, making 3 hydrogen bonds

What is DNA replication?

Result of replication is that each molecule of DNA has one original strand and one new strand

What is helicase?

Enzyme that unzips the DNA by breaking hydrogen bonds between two strands

What is Okazaki?

Fragments of copied DNA created on the lagging strand

What is the leading strand?

The strand that is continuously copied

What is DNA ligase?

Glues Okazaki fragments together

What is DNA polymerase?

Builds new strand by adding nucleotides 5’ to 3’ direction

What is SSB proteins?

Holds the DNA molecule apart during replication

What is the lagging strand?

Strand that is copied discontinuously as fragments

What is DNA primase?

Initiates DNA synthesis by adding short piece of RNA

What is the first step?

DNA helicase unzips the DNA

What is the second step?

Replication fork is formed

What is the third step?

DNA polymerase attaches to the primer

What is the fourth step?

DNA polymerase adds nucleotides 5’ to 3’

What is the fifth step?

Okazaki fragments are bound together by ligase

What is DNA polymerase 1?

Replaces RNA primer with DNA

What is DNA polymerase 2?

Required for pair

What is DNA polymerase 3?

Main enzyme that adds nucleotides in the 5’ to ‘3 direction

What are two differences between DNA replication in prokaryotes and eukaryotes?

In prokaryotes, origin of replication is single and in eukaryotes it is multiple. The rate of replication in prokaryotes occurs in 1000 nucleotides/sec while in eukaryotes it is 50/100 nucleotides/sec

What is telomere?

Noncoding DNA located at the end of chromosomes

What is telomerase?

Can stop the shortening of the telomeres by adding telomeric repeats to the chromosome ends

What is mismatch repair?

If nucleotides are mismatched, enzymes remove and resynthesize part of the DNA

What are two types of repair that occur after replication is complete?

Point and frameshift mutations

What is nucleotide excision repair?

similar to mismatch repair except it is used to replace damaged nucleotides

What is silent?

The incorrect base does not change the amino acid and therefore has no effect on protein sequence

What is missense?

The incorrect base leads to an incorrect amino acid substitution

What is nonsense?

The incorrect base leads to a stop codon