Unit 1 KA2 Structure & Replication of DNA Flashcards
Yummy DNA 😋
What is the repeating unit in DNA called?
Nucleotides
What composes each DNA nucleotide?
- Phosphate
- Deoxyribose Sugar
- Base
What are the 4 DNA bases and what they bond to?
Adenine bonds with Thyamine and Guamine bonds with Cytosine
What shape is DNA?
Double helix
How are the strands of DNA held together?
Through hydrogen bonds between the base pairs
Hydrogen bonds are quite weak, meaning the strands can be pulled apart easily
What makes up the “backbone” of DNA?
Phosphate and deoxyribose sugar
Phosphate-sugar backbone
Why is the sugar-phosphate backbone so strong?
Due to strong chemical bonds between the phosphate of one nucleotide and carbon 3 of another
What does an antiparallel structure mean for DNA?
The strands run in opposite directions
One stand would go from carbon 5 to carbon 3, and the other would go from carbon 3 to carbon 5
What shape do the DNA strands coil into?
A double helix
Name the base pairs of DNA
Adenine - Thymine
Cytosine - Guanine
Before cell division, what must happen to the DNA in the nucleus?
It must be replicated
What enzyme replicates DNA?
DNA polymerase
What are the stages in DNA replication?
- Double helix unwinds
2.Weak hydrogen bonds between base pairs break to form two template strands
3.Template strands expose their bases at a Y-shaped replication fork
4.One strand is a template for the leading strand and the other is a template for the lagging strand
What is the DNA strand with the 3’ end exposed called?
Leading strand
What is the DNA strand with the 5’ end exposed called?
Lagging strand
What is the difference in replication between the leading and lagging strands?
Leading strand Replicates continuously
Lagging strand replicates in fragments (Discontinuously)
Why is the DNA primer required for replication?
To create an existing chain for DNA polyermase to work on
How are new nucleotides added to replicate the template strand?
They align with complimentary base pairs on the template strand and bind to the 3’ end of the primer
What creates ssugar-phosphate bonds?
DNA polymerase
Why does the lagging strand have to be replicated in fragments?
Because the only the 5’ end is exposed, and DNA polymerase can only add nucleotides to the 3’ end
How are the fragments of the lagging strand joined together?
The enzyme ligase joins them together
What are the 5 requirements for DNA replication?
- DNA (to act as a template)
- Primes (to create an existing chain for DNA polymerase to work on)
- Free DNA nucleotides (A,T,G & C)
- Enzymes (DNA polymerase and ligase)
- ATP (energy)
What does PCR stand for?
Polymerase chain reaction
Why is PCR useful for genome sequencing?
Because it amplifies (replicates) DNA
