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Genes and Heredity > Translation > Flashcards

Translation Flashcards

1
Q

How many possible codons are there?

A

64

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2
Q

What is a triplet binding assay?

A

A test which proves synthetic trinucleotides can promote binding of specific tRNAs to ribosomes.

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3
Q

How many sense codons are there?

A

61

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4
Q

Where is the code not universal?

A

In mitochondria

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5
Q

What is tRNA?

A

The adaptor between codons and amino acids.

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6
Q

How does the tRNA link to its amino acid?

A

Through covalent bonding.

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7
Q

What part of the tRNA recognises the codon?

A

The anticodon

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8
Q

What defines the cloverleaf structure of tRNA?

A

4 stems and 4 loops

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9
Q

What do the hydrogen bonds between paired bases of the tRNA result in?

A

Its 3D structure

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10
Q

What is the open reading frame?

A

The protein coding sequence in a gene.

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11
Q

What is meant by the genetic code being degenerate?

A

Most amino acids have more that one codon.

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12
Q

What happens to the tRNA when it binds the amino acid?

A

It becomes charged

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13
Q

How does the tRNA associate with the mRNA molecule?

A

Through the anticodon loop

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14
Q

What is the function of aminoacyl-tRNA synthetase?

A

It catalyses the covalent linkage between the 3’ end of the tRNA and its cognate amino acid.

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15
Q

Which tRNAs does aminoacyl-tRNA synthetase recognise?

A

All isoaccepting tRNAs

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16
Q

How many aminoacyl-tRNA synthetases are there?

A

One per amino acid

17
Q

What did Seymour Benzer discover?

A

That protein synthesis machinery recognises the anticodon not the amino acid associated with the tRNA.

18
Q

What led Seymour Benzer to their discovery?

A

A cysteine charged tRNA was chemically changed to become an alanine charged tRNA. Alanine was then incorporated into the polypeptide chain instead of cysteine.

19
Q

What parts of translation are subject to proofreading?

A

Amino acid selection and tRNA selection.

20
Q

What is the process of kinetic proofreading?

A

If the wrong amino acid is selected the forward reaction is disfavoured and so slows.

21
Q

What is the process of chemical proofreading?

A

If the wrong amino acid is selected the catalytic reaction is reversed.

22
Q

What does proofreading avoid?

A

The need for absolute accuracy.

23
Q

What do sticky mutations result in in mice?

A

A neurodegenerative disease

24
Q

At what loci were sticky mutations found?

A

In the AlaRs gene encoding alanyl-tRNA synthetase.

25
Q

What can a defect in proofreading lead to?

A

A higher level of ser-tRNA ala synthesis (mis charging with serine)

26
Q

How many tRNA molecules are there?

A

Around 30

27
Q

What allows one tRNA to decode more than one codon?

A

Wobble and modified bases.

28
Q

What is the wobble hypothesis?

A

Watson-Crick base pairing rules between anticodon position one and codon position three are relaxed due to flexibility and modifications of the anticodon loop.

29
Q

What is the structure of ribosomes?

A

It consists of two subunits. The larger subunit has three rRNA molecules and 49 different proteins in a precise pattern.
The smaller subunit has one rRNA and 33 proteins.

30
Q

How are ribosomal subunits held together?

A

By ionic and hydrophobic forces.

31
Q

What forms the bulk of RNA structure in bacteria?

A

The 50s crystal

32
Q

What fills the gaps between rRNA?

A

Proteins

33
Q

What catalyses peptide bond formation?

A

The 23s rRNA (ribozyme)

34
Q

How many tRNA binding sites are there on the largest ribosome subunit?

A

Three

35
Q

Where do codon-anticodon interactions between tRNA and mRNA occur?

A

At the P and A sites

36
Q

What is the function of the A (aminoacyl tRNA/entry) site?

A

It binds the anticodon to the charged tRNA.

37
Q

What is the function of the P (peptidyl tRNA/donor) site?

A

It is where the tRNA adds the amino acid to the growing peptide chain.

38
Q

What is the function of the E (exit) site?

A

It is where the tRNA sits before being released from the ribosome.

39
Q

What are the stages of translation?

A

Initiation, elongation and termination

Genes and Heredity (6 decks)

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