Topic 1- Transcription & Translation Flashcards
Describe mRNA
- Made in nucleus during transcription
- carries genetic code from DNA to cytoplasm, used to make protein during translation
Describe tRNA
- in cytoplasm
- amino acid binding site at 1 end
- sequence of 3 bases at other end called anticodon
- carries amino acids used to make proteins to ribosome during translation
Describe (simple) transcription
mRNA copy of a gene is made in nucleus
What starts transcription
When RNA polymerase attaches to DNA double helix at beginning of a gene (start codon)
What is the function of RNA polymerase
Makes complimentary strand of RNA using DNA as template
What happens once complimentary strand of RNA is made?
Polynucleotide strands wind back into double helix
How does RNA polymerase know when to stop transcription
When it reaches a stop codon
Where does the newly made strand of RNA go?
Attaches to ribosome in cytoplasm
What is the second stage of protein synthesis called?
Translation
Describe (simple) translation
Amino acids are joined to form polypeptide chain, according to codons carried by mRNA
Where does translation occur?
At ribosomes in cytoplasm
How does translation start?
tRNA molecule, with anticodon complementary to start codon on mRNA, attaches itself via base pairing
What happens to amino acids brought by tRNA
Join together by peptide bond
What do the linked amino acids produce
A polypeptide chain
When does the process of translation stop?
Until stop codon on mRNA molecule
What sort of proteins are made at free ribosomes?
Proteins that will stay in the cytoplasm
What sort of proteins are made at ribosomes on RER
Proteins that will be excreted or ones that will attach to cell membrane
Process of out of cell protein production?
1) proteins produces at RER are folded and processed in RER
2) transported from ER to Golgi apparatus in vesicles
3) further processed at Golgi
4) proteins pinched into vesicles to be transported around cell or move to cell surface to be excreted by exocytosis
