Overview of translation, tRNA and codon-anticodon interaction

Question 1

Using an arrow diagram, what happens when genes are expressed?

Answer 1

DNA -> mRNA -> Protein

Nucleus — || — cytosol

Question 2

What is the process to get mRNA from DNA?

Answer 2

Transcription

Question 3

What is the process to get protein from mRNA?

Answer 3

Translation

Question 4

How are genes in bacteria arranged?

Answer 4

Closely-packed (with only very short gaps between them) and are commonly co-transcribed to generate polycistronic mRNAs

Question 5

What is meant by ‘cistron’?

Answer 5

‘mRNA coding sequence or ‘open reading frame’ (ORF)

Question 6

How are genes in higher eukaryotes such as animals and plants arranged?

Answer 6

‘Miles apart’ and cannot possibly be co-transcribed. Hence, eukaryotic mRNAs are monocistronic

Question 7

How are genes in lower eukaryotes such as yeast arranged?

Answer 7

Almost as close-packed as in bacteria but they are not co-transcribed

Question 8

How many translation start sites are in prokaryotic mRNA (polycistronic)?

Answer 8

Multiple sites

Question 9

How many translation start sites are in eukaryotic mRNA (monocistronic)?

Answer 9

A single site

Question 10

In all cell types, mRNAs are translated concurrently by..

Answer 10

Multiple ribosomes in structures termed ‘polyribosomes’

Question 11

In eukaryotes, where are mRNAs translated?

Answer 11

In the cytosol

Question 12

tRNA contains ‘odd’ bases and nucleosides such as what?

Answer 12

Uracil (U)
Dihydrouracil (UH2 or DHU)
Thymine (5-methyl-uracil)
Uridine
Pseudouridine
Hypoxanthine
Inosine (I)

Question 13

What type of structure is a ‘cloverleaf’?

Answer 13

Secondary structure

Question 14

What type of structure is the co-axial stacking of mini-helices?

Answer 14

Tertiary structure

Question 15

Posttransciptional chemical modification of eukaryotic rRNA mainly involves..

Answer 15

Ribose methylation and pseudouridylation

In contrast, bacterial rRNA is much less heavily modified

Question 16

Chemical modification of tRNA principally involves..

Answer 16

Base methylation including generation of extravagant derivatives (‘hyper modification’)

Question 17

Describe the interaction between a codon and an anticodon

Answer 17

A triplet base pair interaction via antiparallel strands

Question 18

What happens due to ‘Wobble Pairing’?

Answer 18

tRNAs recognise multiple mRNA codons (1, 2 or 3)

mRNA codons can be recognised by multiple tRNAs

Question 19

There is one aaRS per what?

Answer 19

Amino acid

Question 20

What does aaRS stand for?

Answer 20

Aminoacyl-tRNA synthases

Question 21

What are aaRS named specifically after?

Answer 21

The cognate amino acid

e.g. PheRS, AlaRS, LysRS

Question 22

Each E recognises what>

Answer 22

> = 1 x tRNA

Question 23

aaRS has a crucial role in what?

Answer 23

Fidelity of translation

Question 24

tRNA takes what it’s given by..

Answer 24

aaRS