Gene Expression Flashcards

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1
Q

Where does transcription occur?

A

In the nucleus

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2
Q

What are the 3 stages of transcription?

A

Initiation, elongation and termination

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3
Q

What is the TATA region?

A

A section of DNA in the promoter region that is recognised by transcription factors which then bind to it

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4
Q

What type of RNA Polymerase is used in transcription?

A

Type 2

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5
Q

What type of bonds are formed to create the sugar phosphate backbone?

A

Phosphodiester bonds

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6
Q

What is mRNA capping?

A

Adding a guanine nucleotide to the mRNA via a 5’ to 5’ triphosphate linkage

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7
Q

What is polyadenylation?

A

The addition of lots of A bases onto the end of the mRNA.

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8
Q

How does polyadenylation occur?

A

A signal (termination) sequence is recognised by an endonuclease enzyme which cleaves the sequence and then the A bases can be added

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9
Q

What is splicing?

A

When peptide bonds are broke to remove the introns from the mRNA

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10
Q

What are introns and exons?

A

Introns are non coding DNA sequences whereas exons are coding DNA sequences.

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11
Q

How is translation initiated?

A

Special methionyl tRNA molecules recognise the 5’ cap and bind to it, allowing the 40s ribosome subunit and other proteins to bind. The complex then moves along until a start sequence is recognised and the 60s subunit binds

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12
Q

What enzyme forms the peptide bonds in translation?

A

Peptidyl transferase

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13
Q

How is translocation terminated?

A

When a stop codon is reached a releasing factor protein bind to the A site of the 60s ribosome and water is used to break the peptide strand from the tRNA

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14
Q

What enzyme synthesises ribosomes?

A

RNA Polymerase 1

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15
Q

What subunits are prokaryotic ribosomes made up of?

A

A 50s and a 30s to give a 70s ribosome

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16
Q

What subunits are eukaryotic ribosomes made up of?

A

60s and 40s to give an 80s subunit

17
Q

What enzyme produces tRNA?

A

RNA Polymerase 3

18
Q

What enzyme attaches the amino acids to the tRNA molecules?

A

Aminoacyl tRNA synthetase

19
Q

What is the advantage of wobble bases?

A

There is an increased efficiency of translation as their is more flexibility of which nucleotides can bind

20
Q

Which base in the codon doesn’t have to be paired correctly in wobble bases?

A

The third

21
Q

Which additional nucleoside is found in tRNA molecules?

A

Inosine

22
Q

What complex carries out splicing?

A

A spliceosome

23
Q

What does tetracycline do?

A

Binds to the 30s subunit of bacterial ribosomes and prevents tRNA binding to the A site

24
Q

What does erythromycin do?

A

Binds to the 50s subunit of ribosomes and prevents translocation

25
Q

What does chloramphenicol do?

A

Binds to the 50s subunit of ribosomes and prevents peptidyl transferase