Protein Synthesis Flashcards
Transcription
1) DNA helix unwinds to expose the bases
2) One strand acts as a template
3) This unwinding/unzipping is catalysed by DNA helicase which breaks the hydrogen bonds between bases
4) Free mRNA nucleotides align with the exposed bases via complimentary base pairing
5) The enzyme RNA polymerase bonds the RNA nucleotides together to create a new RNA polymer chain. One entire gene copied
Once copied it leaves the nucleus through the nuclear pores
Splicing
Pre mRNA has to be modified
The introns are spliced out by a protein called a splicesome, this leaves behind the exons which are the coding reigons
Translation
1) Once mRNA has left the nucleus it attaches to a ribosome in the cytoplasm, the ribosome attaches at the start codon
2) The tRNA molecule with the complements anticodon to the start codon aligns opposite the mRNA
3) The ribosome will move along the mRNA molecule to enable another complementary tRNA to attach to the next codon on the mRNA
4) The two amino acids are joined by a peptide bond in a condensation reaction, requires ATP
5) This continues until the ribosome reaches the stop codon at the end of the mRNA molecule. The stop codon does not code for an amino acid therefore the ribosome detaches and translation ends
What is the definition of a mutation?
A change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide
Types of mutation - insertion/addition
Nucleotide randomly inserted into the DNA
Changes the amino acid that would have been coded for by the original base triplet creating a different triplet of bases
Has a knock on effect as it also changes the triplets further on in the DNA sequence - frame shift
May dramatically change amino acid sequence produced and therefore form a non functioning polypeptide
Types of mutations - Deletion
Nucleotide randomly deleted from DNA sequence
Changes amino acid which would have been coded for, also has knock on effects causing a frame shift
May dramatically change amino acid sequence and affect polypeptides ability to function
Types of mutation’s - substitution
A base in the DNA sequence is randomly swapped for a different base.
Only changes the amino acid for the triplet - will not have a knock on effect
May not alter the amino acid sequence of the polypeptide
This is because certain codons may code for the same amino acid as the genetic code is degenerate
What is a mutagenic agent?
Something which increases the rate of mutation.
Ie high energy radiation (X rays and gamma rays)
These damage the DNA molecule and chemicals that alter the DNA structure, or interfere with DNA replication
What is the difference between the genome and the proteome of a cell?
Genonome - complete set of genes in a cell
Proteome - full range of proteins a cell is able to produce
Structure of ATP
3 Phosphate groups
A ribose sugar and adenine base (adenosine)
It is a Nucleotide
Properties of ATP
It only takes a small amount of energy to break the covalent bond holding the last phosphate bond in place
When this bond is broken lots of energy is released
This requires a water molecule so it is a hydrolysis reaction
