Session 8: Gene expression Flashcards
A polynucleotide is..
DNA or RNA
A polypeptide is…
A protein
Making a polynucleotide or a polypeptide requires what 3 things?
Enzymes
Active substrates
A template
What three stages are involved in making a polynucleotide or a polypeptide?
Initiation
Elongation
Termination
What are the enzyme, activated substrates and template needed to make DNA (DNA replication)?
Enzyme: DNA polymerase
Activated substrates: deoxynucleoside triphosphates (dNTPs)
Template: DNA
What are the enzyme, activated substrates and template needed to make RNA (Transcription)?
Enzyme: RNA polymerase
Activated substrates: nucleoside triphosphate (NTPs)
Template: DNA
What are the enzyme, activated substrates and template needed to make a polypeptide (Translation)?
Enzyme: Ribose
Activated substrates: Amino acids
Template: mRNA
What is involved at each stage of DNA replication?
Initiation: recognition of origin of replication initiation proteins and binding of DNA polymerase
Elongation: 5’ to 3’ chain growth
Termination: Replication forks meet
What is the process called that converts DNA into mRNA?
Transcription
What is the process called that converts mRNA into protein?
Translation
What is involved at each stage of Transcription?
Initiation: promoter recognition, transcription of initiation factors binding of RNA polymerase
Elongation: DNA strands unwind and RNA reads the nucleotide sequence and inserts and links together complementary RNA nucleotides (forming pre-mRNA)
Termination: RNA polymerase stops adding nucleotides when a 3’ termination sequence is reached
What happens to the pre-mRNA once it has been made in the nucleus form mature mRNA?
They are processed to remove introns, and the remaining exons are then spliced together to form mature mRNA
What are added to the 5’ and the 3’ ends of the mRNA following its transcription?
5’ end: nucleotide cap
3’ end: poly- A tail
Once the ends have been capped what happened to the mature, processed mRNA?
It leaves the nucleus through a nuclear pore and enters the cytoplasm for translation
During translation what two other forms of RNA interact with mRNA?
ribosomal RNA (rRNA) and transfer RNA (tRNA)
What bond is formed between amino acids?
Peptide bond
What strand is the DNA coding strand?
Is this strand used in transcription?
The strand that is complementary to mRNA (besides the Ts and Us)
No it is not used in transcription
What strand is the DNA template strand?
Is this strand used in transcription?
The template strand is the “non-coding” but this is the strand that is being used to make the mRNA
The mRNA carries the code
Yes this strand is used in transcription
Does transcription proceed from left to right or from right to left on the chromosome?
Neither!!! It proceeds from 5’ end to 3’ end in either direction
What is the purpose of the 5’ cap and the 3’ polyA tail that are added to the pre-mRNA?
To protect against degradation
An unusual attachment provides protection from degradation. The cap is attached by its ______ end to the ______ end of the mRNA.
5’
5’
What happens during polyadenylation and at what end of the RNA does this happen?
At the 3’ end
A sequence is recognised by a specific endonuclease
polyA polymerase adds a poly A tail to the 3’ end
True or false: Ribosomes exist in Prokaryotes and Eukaryotes
True
What are the differences between ribosomes between prokaryotes and eukaryotes?
Prokaryotes:
3 rRNAs and 56 proteins
30S and 50S subunits
70S ribosome
Eukaryotes:
4 rRNAs and 82 proteins
40S and 60S subunits
80S ribosome
What is the clinical importance and relevance of these differences in ribosomes between prokaryotes and eukaryotes?
Can target specific prokaryotic subunits in antibiotics, for example
Ribosomal RNA (rRNA) is made with which polymerase?
RNA polymerase I