Chapter 6- Transcription and translation (2) Flashcards
What is translation?
Conversion of the nucleotide sequence of mRNA into an amino acid sequence of a protein.
mRNA that has left the nucleus is used as a template to assemble a chain of amino acids (polypeptide) with a specific sequence.
Translation requires two components:
1- Ribosomes
2- tRNA
What 4 steps are involved in translation?
1- Initiation
2- Elongation
3- Termination
4- Post- translation processing of the protein
How are mRNA nucleotides read?
They are read consecutively in groups of three- a codon.
What does each codon specify?
Each codon specifies an amino acid used to make a protein chain.
Outline the brief process of translation
Ribosomes read mRNA sequences and bind tRNA which are bound in turn to an amino acid.
Ribosomes place amino acids next to each other in a sequence.
Each codon represents a particular amino acid, and each codon is recognised by specific tRNA.
tRNA has a structure of 3 hairpin loops. One of these hairpin loops contains a sequence called the anticodon- complementary to the mRNA codon.
Explain the initiation stage of translation?
The ribosome binds at the end of the mRNA molecule.
Once it reads a start codon (AUG), it then forms a complex with the large unit of the ribosome and then recruits tRNA.
Start codon = a sequence of adenine, uracil, and guanine.
Explain the elongation stage of translation?
Codons of the mRNA chain determine which tRNA molecule is next recruited into the ribosome.
The tRNA molecules bind with their specific amino acids and bring them to the mRNA molecule on the ribosome.
The anticodon on each tRNA molecule pairs with a complementary codon on the mRNA molecule.
A peptide bond is then formed between the two amino acids.
Explain the termination stage of translation?
The process then continues until a ‘stop’ codon on the mRNA molecule is reached.
Stop codon can be UAA, UAG or UGA.
The amino acid chain then forms the final polypeptide.
What is transcription control?
The most common type of genetic regulation. Responsible for turning mRNA formation on and off.
What is post transcriptional control?
Regulation of the process of turning pre-mRNA into a mature mRNA.
What is translational control?
Regulation of the rate of initiation
What is post translational control?
Regulation of the modification of an inactive protein to form an active protein.
