Protein Synthesis Flashcards
What is transcription?
The process when genes are copied onto a single strand of RNA and transported to a ribosome.
Explain transcription step by step.
1) The section of DNA that contains the gene unwinds and unzips by DNA helicase, beginning at a start codon.
2) Free RNA nucleotides complementary base pair with the antisense strand of DNA.
3) RNA polymerase joins these nucleotides together with phosphodiester bonds.
4) Transcription stops at the end of the gene. The copied strand is called mRNA.
Which strand of DNA is mRNA a copy of? In other words, which strand of DNA contains the code for a protein?
The sense strand.
Which strand of DNA acts as a template strand during transcription?
The antisense strand.
What is the start codon at the beginning of every gene?
Methionine.
What is post-transcriptional modification?
When the pre-mRNA strand is spliced to cut out all the unnecessary introns. Then the exons are joined to make a shorter modified mRNA strand.
What are introns and exons?
Introns are non-coding sequences within genes.
Exons are coding sequences within genes.
What happens in translation?
Step by step.
1) The mRNA binds to the small subunit of the ribosome at its start codon.
2) tRNA with the complementary anticodon binds to the mRNA start codon. It then drops off the amino acid methionine.
3) Another tRNA binds to the next codon and drops of its amino acid.
4) A maximum of 2 tRNAs can be bound to the ribosome at the same time.
5) The amino acids join by a peptide bond and peptidyl transferase catalyses it.
6) This repeats until a stop codon is reached.
What is post-translational modification?
When the amino acid chain is modified before it becomes a fully functional protein.
What is the job of mRNA?
mRNA carries the ‘message’ that codes for a particular protein from the nucleus to the cytoplasm.
What is transfer RNA and what does it do?
tRNA carries amino acids to the ribosome and matches them to their codon on mRNA.
It is one stand folded up into a looped-clover leaf shape.
What is ribosomal RNA and what does it do?
rRNA together with proteins makes ribosomes. It maintains the structural stability of the protein synthesis sequence and catalyses the reaction.
What are the three kinds of RNA?
Messenger RNA
Transfer RNA
Ribosomal RNA
What is a gene?
A section of DNA that contains the complete sequence of of codons to code for one entire protein.
