DNA To Gene Expression Flashcards
What bases are pyrimidines?
C and T
What bases are purines?
A and G
How many hydrogen bonds between bases G andC?
3
How many hydrogen bonds between bases A and T?
2
DNA structure
-Double helix of 2 complementary strands
- composed of nucleotides : sugar, phosphate group and nitrogenous bases
When DNA is replicated what fraction contains the new DNA strand?
1/2
DNA replication simplified
- Replication fork formation
- primer binding
- elongation
- termination
Lagging strand is what direction
5‘ to 3’ direction
Primer binding
-A primer (short RNA piece) binds to a 3’ and of leading strand
Primer binds at starting point for replication
What enzyme unwinds DNA?
DNA helicase
Replication progresses in what direction?
5’ to 3’ direction
Leading strand is in what direction?
3’ to 5’ direction
Elongation stage for leading strand (replication)
DNA polymerase create new strands by adding new base pairs
Elongation stage for lagging strand (replication)
Begins replication by binding multiple primers
Which strand is DNA synthesised continuosly?
Leading strand
On the lagging strand, DNA is synthesised how?
In short fragments (Okazaki)
Leading strand synthesised by what enzyme?
DNA polymerase
Okazaki fragments are joined by what enzymes?
DNA ligases
What enzyme adds pieces of DNA between primers on lagging strand?
Another DNA polymerase
In termination what happens to RNA primers?
They are removed and replaced with bases
Function of telomerase
Adds telomeres at DNA 3’ ends
Termination stage of DNA replication.
- RNA primers removed and replaced
- Okazaki fragments joined
-Telomerase adds telomeres - parent and complementary strands coil into double helix
Function of topoisomerases
Unwind and rewind DNA strands to prevent DNA from getting tangled
RNA structure
Single stranded, composed of nucleotides
RNA is synthesised in what direction?
5’ to 3’ direction
Transcription steps
1 initiation
2 promoter clearance
3 elongation
4 termination
Order of DNA to gone expression
- DNA replication
- transcription
- mRNA processing
- Translation
Protein folding
Initiation stage of transcription
- RNA polymerase and cofactors unwind and bind to DNA ( at promoter region)
Approx 14 base pairs are exposed each time
Promoter clearance stage in transcription
- Promoter (DNA sequence) signals which DNA strand is transcribed
- RNA polymerase clears the promoter once the first bond has been synthesised