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Molecules, Cells and Diseases (MCD) and Epidemiology in Practice (EiP) > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

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Organic Chemistry 101 flashcards
1
Q

What is the first amino acid in a protein translated from mitochondrial mRNA?

A

Formylmethionine (fMet).

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2
Q

What is chromatin?

A

DNA + associated proteins

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3
Q

What are nucleosomes?

A

DNA wrapped around a core of histone proteins - an example of chromatin.

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4
Q

Name the purines

A

Adenine and guanine.

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5
Q

Describe charges in DNA.

A 
Phosphate groups (backbone) negative
Histones positive
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6
Q

What direction is DNA synthesised?

A

5’ to 3’ of new strand. dNTP added to 3’ end of primer.

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7
Q

What is DNA primase?

A

An RNA polymerase which produces an RNA primer.

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8
Q

How is an incorrect nucleotide removed?

A

3’ to 5’ exonuclease activity of DNA polymerase.

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9
Q

Which is the antisense strand?

A

The template strand.

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10
Q

What does RNA polymerase II do?

A

Transcribes encoding mRNA.

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11
Q

What is the promoter gene?

A

The DNA sequence at which the transcription complex assembles.

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12
Q

How do transcription factors facilitate transcription?

A

They remodel chromatin. Hyperacetylation = gene expression. Hypoacetylation = gene repression. (They upregulate or downregulate the basal transcription complex).

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13
Q

For stability, what 2 features are added to the primary transcript (pre-mRNA)?

A

A 5’ cap - a modified nucleotide (7-methylguanosine)

A polyA tail, 11-30 bases downstream of AAUAAA.

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14
Q

What is alternative splicing?

A

Some exons are ignored, e.g. a mutate exon in dystrophin which causes DMD is ignored.

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15
Q

What is a tRNA with an amino acid attached called?

A

Charged

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16
Q

Name the 2 sites of the large ribosomal subunit.

A

The P (peptidyl) site and A (amino acyl) site.

17
Q

What are elongation factors (EFs)?

A

Proteins which promote the movement of ribosomes along mRNA using GTP.

18
Q

Why is GTP used?

A

Increases efficient and accuracy of translation by providing pauses (GPT hydrolysis) allowing incorrect base pairs to dissociate.

19
Q

What happens when a stop codon is recognised?

A

A release factor binds to the A site, causing the dissociation of the release factor and ribosomes.

20
Q

What recognises the signal sequence on a protein destined for the ER?

A

A SRP (signal recognition particle).

21
Q

Which enzyme cleaves the signal sequence of a protein being translated on the surface of the rER?

A

Signal peptidase

22
Q

How are transmembrane proteins held in the membrane?

A

They encode one or more hydrophobic sequences.

23
Q

What does the energy needed to break the H-bonds between DNA bases and hence denature the DNA depend on?

A

Strand length
Base composition (G-C = 3 H-bonds)
Chemical environment: monovalent cations stabilise the DNA duplex. Denaturants destabilise.

24
Q

What is hybridisation stringency?

A

The power to distinguish between related sequences.

25
Q

Which handed double helix is DNA and how many base pairs are there per helical turn?

A

Right-handed double helix. 10bp per helical turn.

26
Q

What are teratogens?

A

Agents which interfere with normal embryonic or foetal development.

27
Q

Roughly how many genes and proteomes are there in the human genome and proteome respectively?

A

25,000 genes: 1,000,000 proteins.

28
Q

Describe the process of RNAi

A

dsRNAs and shRNAs are digested into fragments of 21-25bp by DICER using RNAse III like endonuclease activity, forming siRNAs.
siRNA guided endonuclease activity removes the passenger strand, requiring Argonaute-Piwi proteins.
This forms the RNA-induced splicing complex (RISC) which recognises and cleaves target mRNA molecules.

29
Q

How are tRNAs charged?

A

Amino acid binds to aminoacyl tRNA synthetase, which cleaves pyrophosphate from ATP and binds the AMP to the AA: the AA is adenylated.
The adenylated AA is then attached to the tRNA: AMP and aminoacyl tRNA synthase detach leaving the charged tRNA.

30
Q

What is breaking the hydrogen bonds to separate strands of DNA called? How can it be done?
What is encouraging the bonds to reform called?

A

MELTING.
High temperature of low salt environment.
REANNEALING.

31
Q

How many base pairs wrap around a single histone octamer?

A

150bp.

32
Q

Detail the macrostructure of DNA

A

Double helix: nucleosome: 30nm fibre: chromatin loops: chromosome.

33
Q

What constitutes the gene promoter region?

A

The TATA box/ sequence and the transcription factor binding site.

34
Q

What does TFII D do?

A

Contains TATA binding protein (TBP) and TBP accessory factors (TAFs).
Binds to TATA sequence and partially unwinds the DNA by widening the minor groove.

35
Q

What does TFII F do?

A

Binds to RNA polymerase II which then binds to TFII B.

36
Q

What does the splice donor site always start with and the splice acceptor site always end with?

A

GU

Pyrimidine 15 N C AG

37
Q

What are the start and stop codons?

A

Start: AUG
End: UAA, UGA, UAG

Molecules, Cells and Diseases (MCD) and Epidemiology in Practice (EiP) (9 decks)

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