Lecture 5 - DNA Replication Flashcards
Why do 2 strands of DNA separate
So that the chromosomes can be copied
Why do cells need to replicate?
To repair damaged cells
For growth
To produce 2 identical daughter cells
3 Components of DNA
Phosphate
Deoxyribose
Nitrogen Base
Structure of DNA
Store of genetic information
Polymer of nucleotides
Pentose sugar, nitrogenous bases and a phosphate group
Double helix (2 strands) held by hydrogen bases (antiparallel)
Pairs adenine-thymine, cytosine-guanine
Give 3 features of DNA and explain how they important in semi-conservative
Weak Hydrogen bonds always 2 strands to separate
2 strands so both can act as templates
Complimentary base pairs allows accurate replication
Explain Semi-Conservative Replication
DNA unwinds/untwists as DNA helices breaks the hydrogen bonds between basses
Original strand is a template. Free-floating DNA nucleotides are attracted to complementary exposed bases
Condensation reactions join the adjacent nucleotides (catalysed by DNA polymerase). Hydrogen bonds form between the bases.
Two Strands retwist
What does DNA Helicase do
DNA helicase breaks hydrogen bonds between bases
What does DNA polymerase do
Condensation reactions join the adjacent nucleotides - catalysed by DNA polymerase
Why is DNA replication carefully controlled
To preserve the genetic information
What is a mutation
Changes in the genome
Name me type of mutations
Substitution
Deletion
Addition
Duplication
Inversion
Translocation- sequences of base
How many base pairs are there in one full turn of the DNA double helix?
10
Analysis of a sample of DNA found that 20% of the bases were adenine. What percentage of the bases would be pyrimidines?
50%
Which technique was used to determine the double-helical structure of DNA?
X-ray crystallography
Which is the first step of semi-conservative replication?
Unwinding of the double helix
During DNA replication, the new strand is made in which direction? 5 prime to what?
3 prime
Before cell division, what does DNA need to do?
(copy itself, replicate, copy)
