Chapter 17: Gene Expression From Gene to Protein Flashcards
What is transcription?
Conversion of DNA to RNA
What is translation?
Conversion of RNA to Protein
How does DNA encode information for a protein?
Uses nonoverlapping nucleotide words (3 letters each)
What is a template strand?
The strand that is looked at when making an RNA match
What is a codon?
A sequence of 3 DNA or RNA nucleotides
In what direction is DNA read?
3’ —-> 5’
In what direction is mRNA made?
5’ —-> 3’
In what direction is mRNA read?
5’ —-> 3’
What is the start codon?
Where you start reading from
- AUG
What is the stop codon?
Where you stop reading from
- UAA
- UAG
- UGA
What are the 3 stages of transcription and what happens in each one?
- Initiation
- RNA polymerase binds to the promoter on the DNA
- the double helix opens so that the template strand can be read to make mRNA
- Elongation
- mRNA is made in the 5’ to 3’ direction
- Termination
- after the polyadenylation signal (AAUAA) is reached, RNA polymerase detaches
- complete mRNA transcript is released
What are the two things required for mRNA to complete translation in eukaryotes?
A 5’ cap and a Poly-A Tail
What is a 5’ cap?
- extra nucleotides that consist of phosphates
- It is attached to the 5’ end of mRNA
What is a Poly-A Tail?
- a long chain of A nucleotides
- AAAAAAAAA
- It is attached to the 3’ end of mRNA
What’s a secondary purpose of the 5’ cap and the Poly-A Tail?
To protect the protein content within the mRNA strand from degradation
What is the UTR?
Untranslated region
It’s on both sides of the coding sequence (start and stop codons).
These are buffers that are not read.
What happens after an eukaryotic mRNA is processed?
It’s ready for RNA splicing
What are exons?
Section of mRNA that will undergo translation and decode a protein.
What are introns?
Noncoding sections of RNA transcript
What is RNA splicing and how does it work?
Introns are removed before the mRNA undergoes translation.
A protein comes along and removes the introns. The exons then join together to make one long protein mRNA.
If a protein contains multiple exons, how many proteins can be made from a single mRNA transcript?
7
Possible proteins made:
1, 2, 3, 1+2, 2+3, 1+3, 1+2+3
Where does translation occur?
Ribosomes in the cytoplasm
Explain the steps of translation in the ribosome.
- The mRNA strand starts going through the ribosome. Once it reads an AUG, tRNAs come along and deposits corresponding codons (UAC etc).
- As the mRNA strand moves through the ribosome, the APE conveyer belt releases the E rRNA (no longer useful) and the P and A tRNAs start making a growing polypeptide.
- This will continue until a stop codon is reached.
What is an anticodon?
3 nucleotides located on a tRNA
The sock thingy
What is the tRNA anticodon that would bind to the sequence GUU on an mRNA molecule?
CAA
If a tRNA anticodon is complementary to the mRNA codon GGG, what amino acid would you expect it to carry?
The amino acid on the chart that corresponds to GGG
NOT CCC!
If the questions asks for an amino acid, use the mRNA codon, not the tRNA anticodon.
When do you use the anticodon to read the chart?
Only when she asks for it.
What is a point mutation?
When one letter changes in the sequence
What is insertion and deletion mutation?
Addition of deletion of single or grouped nucleotides
What is a silent point mutation?
There’s a mutation but it does not affect the amino acid chosen from the table
(No change seen)
What is a missense point mutation?
The letter changed caused the table to give a different amino acid.
(Noticeable change)
What is a nonsense point mutation?
This is when a letter change causes a stop codon in the sequence.
(Noticeable change because the protein stops)
What is a wild type?
Normal allele at the locus
Which is more important, the first position or third position of a single codon?
1st
