DNA & RNA Flashcards
Describe the structure of DNA.
Double helix made up of phosphate, deoxyribose and bases
Which bases bind to which ones?
Purines bond with pyrimidines
A - T
G - C
How many H bonds form between the bases?
A - T 2 H bonds
G - C 3 H bonds
What are nucleosomes?
DNA wrapped around histone proteins
What’s the difference between RNA and DNA structure?
Single stranded
Ribose instead of deoxyribose
Uracil replaces thymine
What’s the difference between RNA and DNA function?
DNA is the blueprint of biological guidelines that a organism must follow to exist.
RNA transfers genetic code needed for the creation of proteins from the nucleus to the ribosomes.
What is DNA replication?
Producing 2 identical replicas from 1 original DNA molecule
Describe the steps of DNA replication.
Breaking of hydrogen bonds between bases of strands by HELICASE
RNA POLYMERASE constructs an RNA primer which guides DNA POLYMERASE to its site of action
DNA POLYMERASE joins the free nucleotides to the bases of the parent strand, creating a new strand
DNA LIGASE joins the old and new strand together
Which way does DNA polymerase read the exposed DNA?
From 3’ to 5’
Why is DNA replication referred to as semi-conservative?
Only one strand of the daughter strand is newly synthesised
One is conserved from the parent strand
What is transcription?
DNA to mRNA
the mRNA can then be used to make a protein!
Describe transcription.
RNA POLYMERASE separates the two strands of DNA and binds to the promoter region on one strand
It then adds matching RNA nucleotides to the complementary nucleotides of one DNA strand
It then helps to form the sugar-phosphate backbone
An mRNA strand is formed!
Which direction does transcription go in?
5’ to 3’ direction
Name 3 post-transcriptional modification processes
5’ capping
Polyadneylation
Splicing
What is 5’ capping?
The 5’ capping reaction replaces the triphosphate group at the 5’ end of the RNA chain with a special nucleotide referred to as the 5’ cap.
Helps with mRNA recognition by the ribosome during translation
What is polyadenylation?
A modification that takes place on the 3’ end of the RNA.
A poly A tail is added
What is splicing?
Editing introns out of the RNA
What is an exon and intron?
Exon - section that codes for a protein
Intron - section that doesn’t code for anything
Where does transcription take place?
Nucleus
Where does translation occur?
Cytoplasm
What is translation? Describe it!
mRNA to protein
Ribosome assembles around the target mRNA. The 1st tRNA is attached as the start codon
The tRNA transfers an amino acid to the tRNA corresponding to the next codon
The ribosome moves to the next mRNA codon to continue the process, creating a chain
Stops when a stop codon is reached
What is a codon?
3 base pairs in a row which code to make 1 amino acid - AGC for example
What’s a nonsense mutation?
A mutation that results in a premature stop codon
Results in a truncated, incomplete and non-functional protein
What’s a missense mutation?
A mutation where a single nucleotide change results in a codon that codes for a different amino acid
