Human Cells Unit 1 KA2 Flashcards
Structure and Replication of DNA
What are DNA Nucleotides made up of? (3)
1) Deoxyribose sugar
2) Phosphate
3) Base
What four bases are found in a DNA Nucleotide?
1) Adenine
2) Thymine
3) Guanine
4) Cytosine
What are the two Complementary base pairs?
1) Adenine + Thymine
2) Guanine + Cytosine
What does DNA consist of?
DNA consists of repeating units called nucleotides
What is joined to the Carbon 3 end?
Deoxyribose is joined at the Carbon 3 end in each chain
What is joined to the Carbon 5 end?
The Phosphate group is joined at the Carbon 5 end in each chain
What is the structure of DNA?
Two strands of nucleotides running in antiparallel directions, held together by weak hydrogen bonds, forming a double helix
What must happen before cell division occurs?
Before cell division occurs, the DNA in the nucleus must be replicated
Which Enzyme replicates DNA?
DNA Polymerase replicates DNA
What are the four stages of DNA Replication?
1) Double helix unwinds
2) Hydrogen bonds between base pairs break forming two template strands
3) Template strands become stabilised and expose bases at Y shaped replication fork
4) One strand of the replication fork is a template for the Leading strand, the other for the Lagging strand
Which template strand forms the Leading strand?
The template strand with the 3’ end is continuous and forms the Leading strand
What must be present to create an existing chain for DNA Polymerase to work on?
A DNA Primer must be present for DNA Polymerase to work on
Which end of the Primer are DNA Nucleotides added to?
DNA Nucleotides are added to the 3’ end of the Primer
Which template strand forms the Lagging strand?
The template strand with the 5’ end is discontinuous, replicating in fragments which form the Laggng strand
Which Enzyme joins fragments together to create the Lagging strand?
Ligase joins fragments together to create the Lagging strand
What are the requirements for DNA Replication? (5)
1) DNA (acts as a template)
2) Primers (creates existing chain for DNA polymerase)
3) DNA Nucleotides (A+T, G+C)
4) Enzymes (DNA Polymerase, Ligase)
5) ATP (energy)
Why is DNA Replication so important?
DNA Replication is important to ensure that, before a cell divides, theres the correct quantity of DNA to fill the nuclei of both new cells
What could happen if theres an error in the process of DNA Replication?
If an error occurs in the process of DNA Replication, a non-functional protein could be produced which may have a harmful effect. (See KA 4)
What is the Polymerase Chain Reaction (PCR)?
PCR is a method used to amplify DNA
What happens in PCR Stage 1/3?
In Stage 1 of PCR -
DNA is heated to between 92-98C
to seperate the strands
What happens in PCR Stage 2/3?
In Stage 2 of PCR -
DNA is cooled to between 50-65C
to allow primers to bind
What happens in PCR Stage 3/3?
In Stage 3 of PCR -
DNA is heated to between 70-80C
so heat tolerant DNA polymerase can replicate the DNA
What are the practical applications of PCR?
(3)
1) Amplify DNA to solve crimes
2) Settle paternity disputes
3) Diagnose genetic disorders
