Transcription and Translation Flashcards
What is the order from gene to protein?
DNA–>RNA–>Protein
Where does transcription occur in eukaryotes?
The nucleus
What does transcription do?
It creates a single stranded copy of mRNA that can leave the nucleus
What are the 3 steps of transcription?
Initiation, elongation, and termination
What happens during initiation in transcription?
Transcription factors and RNA polymerase bind to the promoter of the gene
What happens during elongation in transcription?
DNA is unwound and RNA polymerase creates a strand of mRNA which is complementary to the template strand of DNA (the RNA polymerase synthesizes the mRNA in the 5’ to 3’ direction)
What happens during termination in transcription?
Transcription proceeds until the polymerase reaches the terminator sequence which then causes the enzyme to disassociate from the DNA
What direction is the mRNA synthesized during the elongation step of transcription?
5’ to 3’
What must happen to RNA before it can be transported to the cytoplasm and then what is the next step once the RNA reaches the cytoplasm?
The RNA must be modified in the nucleus and then once it reaches the cytoplasm, translation can occur
What are 3 important functions of RNA processing?
Facilitates export from nucleus, Protects from degradation in the cytoplasm, and helps ribosomes attach to the 5’ end for translation
What is the term used for noncoding DNA segments?
Introns
What is the term used for coding DNA segments?
Exons
What is the function of a spliceosome?
To cut out introns and join the exons together
Why do we have introns?
They contain sequences which play a role in regulating gene expression and they also allow a single gene to code for more than one polypeptide.
What does alternative RNA splicing do?
It can leave some exons out of the final transcript which allows humans to make a wider variety of proteins.
Where does translation occur?
In the cytoplasm
How many bases are read at a time in mRNA to build a polypeptide? What is the term for it?
3;codon
What are the 2 key players in translation?
tRNAs and Ribosomes
What does tRNA do?
Translates message from nucleic acids to amino acids
What does tRNA contain?
An anticodon which is a triplet that is complementary to codon on the mRNA
True/False: tRNAs can carry any protein. It does not have to be specific.
False
What are aminoacyl-tRNA synthetases?
Enzymes that attach the amino acid to the tRNA
tRNA with an amino acid attached is “___”
Charged
What consists of a small and large subunit composed of protein and ribosomal RNA (rRNA)?
Ribosomes
In terms of medicine, how are eukaryotic and prokaryotic ribosomes different?
Some antibiotics inactivate the bacterial ribosomes without harming our own
What catalyzes the formation of peptide bonds, the rRNA or the protein?
rRNA
What are the 3 steps of Translation?
Initiation, elongation, and termination
What happens during initiation in translation?
A small unit of the ribosome, with the initiator tRNA, binds to leader sequence of mRNA and scans for AUG
What happens during elongation in translation?
Ribosome moves along mRNA adding amino acids to the growing polypeptide chain
What happens during termination in translation?
Ribosome hits a stop codon and the subunits separate and the polypeptide is released
What is required for elongation in translation?
protein (elongation factors) and energy
What are the 3 sites of the ribosome during elongation?
E site, P site, and A site
What is the E site?
It’s where empty tRNA exits
What is the P site?
It’s where the tRNA is with the growing polypeptide
What is the A site?
It’s where the incoming/active tRNA is
What is the role of a release factor during termination in translation?
It binds to the stop codon in the A site and causes the polypeptide to be released. Once this is done the translation assembly breaks apart.
What happens to the polypeptide after completing translation?
It must undergo correct secondary and tertiary folding
