Intro to DNA II Flashcards
What joins the base pairs across DNA molecules
Hydrogen bonds join base pairs across the centre of the DNA molecule
How many hydrogen bonds between G-C basepair
G-C base pair has 3 hydrogen bonds
How many hydrogen bonds between A- T basepair
A-T base pair has 2 hydrogen bonds
How many hydrogen bonds between A- U basepair
A-U basepair has 2 hydrogen bonds
Which base pair if the strongerst
G-C base pair has it has 3 hydrogen bonds compared to 2
What is the distance between the H bonds in Base pairs (2)
Between C=O and N-H is 2.9 A
Between N- H and C=N-c is 3.0 A
What does it mean when DNA strands are complementary and anti-parallel
3 Prime head binds to the opposing complementary strand, the 5 Prime head of the molecule.
Therefore despite both base pairs having identical DNA sequences, they are bound to each other in opposite directions
In what direction does the coding strand run
Coding strand runs from 5’ to 3’
In what direction does the complementary strand run
Complementary strand runs from 3’ to 5’
At what part of the cell cycle is DNA replicated
DNA is replicated during the S phase of the cell cycle
What direction is chain growth
Chain growth is directional, from 5’ to 3’
What is a stepwise Reaction
a stepwise reaction is a chemical reaction with one or more reaction intermediates.
What are the three stages of DNA replication?
- Initiation
- Elongation
- Termination
What is the difference in chromosomes between Eukaryotes and Prokaryotes
Chromosomes are linear (and larger) in Eukaryotes
What is a leading strand?
The leading strand is a single DNA strand that, during DNA replication, is replicated in the 3’ – 5’ direction
(same direction as the replication fork).
What is the Laging strand?
The lagging strand is a single DNA strand that, during DNA replication, is replicated in the 5′ – 3′ direction
(opposite direction to the replication fork).
Eukaryotic DNA replication - initiation
Kickstarted by primase (enzyme) – a short RNA primer is made
This permits DNA polymerase binds at the 3’ end of a strand within the origin
Eukaryotic DNA replication - elongation
As elongation proceeds, a second DNA polymerase binds to the 3’ end of the lagging strand
The lagging strand is copied in a series of short fragments called Okazaki fragments
This occurs because the DNA is still being unwound as the lagging strand is copied
Multiple different DNA polymerases have to bind in sequence to make these small copies - CALLED OKAZAKI Fragments.
DNA ligase stitches the Okazaki fragments together
The newly formed DNA is wound up into a helix
Eukaryotic DNA replication - termination
Eventually, two replication bubbles meet
DNA ligase joins together the different fragments
Two new strands of DNA have been produced
What is the structure of an Unreplicated Chromosome
2 Arms
What is the structure of a replicated chromosome
4 Arms, Two sister chromatids attached in the middle by a Centromere
What does one chromosome equal to
One chromosome = One DNA molecule
How many Chromosomes and BP’s in a nucleus
46 chromosomes (22 autosome pairs + 2 sex chromosomes),
containing about 3 billion base pairs (bp) of DNA in total.
Structure and components of nucleic acid
Nucleic acids are polynucleotides—
long chainlike molecules composed of a series of nearly identical building blocks called nucleotides.
Each nucleotide consists of a nitrogen-containing aromatic base
attached to a pentose (five-carbon) sugar, which is in turn attached to a phosphate group.
