Intro To Molecular Biology 4

Question 1

Where does mRNA exit through from nucleus into membrane?

Answer 1

Nuclear pore

Question 2

Structure of nuclear pore:

Answer 2

Have proteins (disordered plug) to prevent other substances accidentally getting through

Cytosolic and nuclear fibril

Question 3

What does a cap-binding protein do?

Answer 3

Leads mRNA through pore

Question 4

What does an exon-junction-complex do?

Answer 4

Ensure full length protein is translated

Question 5

Tyopes of mutations:

Answer 5

Deletion

Insertion

Substitution

Question 6

What is deletion?

Answer 6

Base pair deleted

Leads to frameshift and nonsense (changes amino acid to stop)c

Question 7

What’s insertion?

Answer 7

Base pair inserted

Leads to frameshift and nonsense (changes amino acid to stop)

Question 8

What’s substitution?

Answer 8

Base pair substituted/replaced with different base pair

Leads to missence mutation (amino acid changed)

Question 9

What is a silent mutation?

Answer 9

Doesn’t change amino acid

Question 10

What defines the starting point at which to read codons on mRNA?

Answer 10

Initiation codon

AUG = methionine

Question 11

What’s the 5’ non-coding region?

Answer 11

Guide for machinery to start translation at AUG

Question 12

What defines the ending point at which codons are read on mRNA?

Answer 12

Stop codon

Question 13

What is the adapter between the codon and specific amino acid?

Answer 13

Transfer RNA

TRNA

Question 14

How does tRNA bind to mRNA?

Answer 14

Anti-codon loop on tRNA base-pairs with codon on mRNA

Question 15

How does the right amino acid get added to the right tRNA?

Answer 15

Aminoacyl-tRNA synthetases

Question 16

Describe structure of tRNA:

Answer 16

Clover-leaf

Attached amino acid on 3’ end

Anticodon in anticodon loop

Question 17

How does Aminoacyl-tRNA synthetase work?

Answer 17

Activates amino acid and ATP

Amino-acyl is added to tRNA

Question 18

Activation of amino acid:

Answer 18

Enzyme + amino acid + ATP —-> enzyme + PPi

Question 19

Transfer of amino-acyl group to tRNA:

Answer 19

tRNA + enzyme —-> amino-acyl-tRNA + enzyme

Question 20

What does the acceptor stem do on tRNA?

Answer 20

Site where amino acid is added

Question 21

What does editing site do on aminoacyl-tRNA synthetase?

Answer 21

Verifies tRNA charged with right amino acid

Question 22

Large subunit on ribosome:

Answer 22

23s rRNA

50 proteins

Catalytic

Question 23

Small subunit on ribosomes:

Answer 23

18s rRNA

30 proteins

Binds tRNAs

Question 24

How many binding sites do ribosomes have?

Answer 24

One for mRNA

Three for tRNA

Question 25

Three phases of translation:

Answer 25

Initiation

Elongation

Termination

Question 26

What happens in initiation?

Answer 26

5’ cap structure of mRNA recognised

Ribosomes scan through 5’ non-coding region until initiation codon found

Question 27

What’s required for initialisation?

Answer 27

Initiation factors

Question 28

What happens in elongation?

Answer 28

Correct tRNAs bind

Peptide binds made between amino acids

Question 29

What happens in termination?

Answer 29

Termination codon reached

Bond between protein and last tRNA is broken

Whole complex disassociates

Question 30

What is required in termination?

Answer 30

Release factors

Question 31

What’s polymorphism?

Answer 31

Minor change in sequence

Main cause of genetic variation

Question 32

What happens after translation?

Answer 32

Translocation to relevant part of cell

Protein folding

Post-translational modification

Question 33

Effects of mutations:

Answer 33

No transcription

Protein incorrectly processed

Inappropriately regulated

Inappropriate function

Unstable protein