Translation Flashcards by Rebecca Webb

What regions does a gene contain?

5’ end
3’ end
Promoter region
Coding region
Terminator region

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What feature of DNA ensures genes are expressed at the correct time in the correct time?

Upstream enhancers

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What do upstream enhancers allow?

Activators to bind

- Attachment of transcription factors to the promoter sequence

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What is the promoter region?

An area on the 5’ end upstream of the gene. It acts as a control point for transcription

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Where do transcription factors bind?

Specific motifs within the promoter region

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What is sometimes present within the promoter region

TATAA box consisting of the nucleobases T and A

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What does the TATAA box allow?

Allows RNA polymerase and transcription factors to recognise the sequence to be transcribed

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What do genes without a TATA box rely on?

The binding of transcription factors to specific motifs in the promoter region 5’ of the coding region

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What is the role of insulators on a gene?

Protect the inner sequence to ensure expression

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What sequences does pre-mRNA contain?

Leader, Introns, Exons and Trailers

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What sequences in pre-mRNA are spliced?

Introns

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What sequences in pre-mRNA form the mature mRNA?

Leader, Exons and Trailer

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What sequences in mRNA are translated?

Exons

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What can the leader and trailer sequences in mRNA be referred to as?

UTR

-Un Translated Regions

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What is the Reading frame?

Sequence between the leader and trailer sequences (exons)

Sequence that is transcribed

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What does mRNA length rely on?

Length of transcribed gene

Why will mRNA sequences differ?

Different reading frames

- Different leader and trailor regions

What is present in the final mRNA sequence in the cytoplasm?

5’ cap
Exons
3’ poly-a-tail

What determines the nature and shape of the polypeptide chain?

Combination of amino acids which determines the different bonds and interactions e.g. hydrophobic and hydrophilic interactions

Size of a ribosome

80s

What occurs at a ribosome?

Translation

Where are translational ribosomes located?

Rough endoplasmic reticulum

What is the ribosome made up of?

2 subunits

When do both subunits of the ribosome combine?

When methylamine is present in the A-site of the 40s unit

What are the two binding sites within a ribosome and what bins?

P site and A site - Peptidyl and aminocetyl - Charged tRNA's

What is the role of tRNA?

Brings amino acids to the ribosomes during translation to be assembled into polypeptide chains

What codes for tRNA?

tRNA genes

Where does the amino acid bind to the tRNA?

CCA at the 3' end

What is the role of aminoacyl - tRNA synthase?

Adds the correct amino acid to its specific tRNA in the process of aminoacylation One for every amino acid (20)

What is the process of charging tRNA?

- Uncharged tRNA is identified by its synthetase by a small number of bases - Amino acid associated with the enzyme binds to the active binding site - ATP binds to enzyme - 2 phosphate groups are released - Amino acid and ATP bind to form the aa-AMP enzyme and 2 phosphate groups - Enzyme changes shape - uncharged tRNA sits in a lower active binding site displacing the AMP - aa-tRNA is released - Covalent bonds form between carboxyl group of the amino acid and the hydroxyl group of the pentose sugar of the tRNA - Enzyme changes shape and changes back ready to charge the next tRNA

When does the ribosome form?

- 40s and 60s sub units are separate | - Ribosome does not form until the methylamine has bound to the 40s sub units

How does a polypeptide form?

- Charged tRNA comes to the A site - Peptide bond forms between amino on the P site and the A site - Once the peptide bond has formed the uncharged tRNA is ejected - Stop codon causes release factor 1 to bind - Ribosomal complex splits - RNA transcript is free to be translated again - Ribosomes can be recycled - More than one ribosome can translate a mRNA at one time simultaneously producing many polypeptides from a single mRNA - Important genes are highly active so a lot of transcripts so a lot of translation

What are the different mutations?

Substitution, insertion and deletion

What is a silent mutation

Same protein is syntheisised or mutation occurs outside of the transcribed sequence

What is a nonsense mutation?

Stop codon introduced too early and peptide is too small

What is a missence mutation?

Small change in peptide sequence which could have a large or small impact

What is a frameshift?

Bases are added (addition or insertion) or removed (deletion) changing the open reading frame introducing extensive missense or nonsense. If 3 bases are added or removed there will be no frameshift