Topic 4 - DNA & Protein Synthesis Flashcards
What is a genome?
The complete set of genes in a cell.
What is a proteome?
The full range of proteins that the cell is able to produce.
What is the function of mRNA?
Carries genetic information from the DNA to the ribosomes.
What is the shape of mRNA?
Linear
What is the length of mRNA?
Longer
Does mRNA contain hydrogen bonds?
No
Does mRNA contain an amino acid binding site?
No
Is mRNA a codon or an anti-codon?
Codon
What is the function of tRNA?
Transports amino acids to the ribosomes to build proteins.
What is the shape of tRNA?
Clover-leaf
What is the length of tRNA?
Shorter
Does tRNA contain hydrogen bonds?
Yes
Does tRNA contain an amino acid binding site?
Yes
Is tRNA a codon or an anti-codon?
Anticodon
What are the three steps to protein synthesis?
1) Transcription
2) Splicing
3) Translation
What is transcription?
Transcription is the initial step in the synthesis of proteins. It involves creating an mRNA copy of a gene from the DNA template.
Where does transcription take place?
In the nucleus.
Describe the process of transcription.
Step 1) RNA polymerase binds to the DNA.
Step 2) The hydrogen bonds between bases are broken, causing the two strands of the double helix to separate.
Step 3) The nucleotides on the template strand bind to complementary mRNA nucleotides present in the nucleus by hydrogen bonding. (A+U) and (G+C).
Step 4) RNA polymerase catalyses the formation of phosphodiester bonds between the mRNA nucleotides, forming pre-mRNA.
Step 5) The DNA strands re-join behind the pre-mRNA and when the RNA polymerase reaches the stop codon, it detaches.
Describe the process of splicing of pre-mRNA.
1) Only occurs in eukaryotic cells.
2) Removes the non-functioning introns from the pre-mRNA sequence.
3) In prokaryotes, mRNA is directly produced from transcription without any splicing.
What is translation?
Translation is the process of decoding the information in mRNA to synthesise a polypeptide chain, with the help of tRNA. This chain then folds into a functional protein.
Where does translation take place?
Translation occurs in the cytoplasm, on the ribosome.
Describe the process of translation.
Step 1) The ribosome attaches to the mRNA strand at the start codon.
Step 2) A tRNA with a complementary anticodon to the first mRNA codon pairs with the codon on the mRNA.
Step 3) A second tRNA molecule with an anticodon complementary to the next mRNA codon, and also carrying a specific amino acid, attaches to the mRNA.
Step 4) A peptide bond forms between the two amino acids on the tRNAs (with the use of ATP).
Step 5) The ribosome moves along the mRNA to the next codon so the first tRNA is released and a new tRNA arrives at the next codon.
Step 6) The sequence continues until the ribosome reaches a stop codon on mRNA and the completed polypeptide chain detaches from the ribosome.
