Gene Expression

Question 1

In which direction is mRNA produced?

Answer 1

In the 5’—->3’ direction

Question 2

In which direction are proteins made?

Answer 2

From the n terminus end to the c terminus end

Question 3

A gene is not a direct code for a protein, part of it is…

Answer 3

Introns (spliced out)

Initiation and termination signals

Question 4

Making a polypeptide/polynucleotide/dna replication follows which 3 stage process?

Answer 4

Initiation
Elongation
Termination

Question 5

How is dna replication initiated?

Answer 5

Recognition of origin of replication

Initiation proteins recruit DNA polymerase

Question 6

In both DNA replication and transcription, what happens in the elongation stages?

Answer 6

There is 5’—>3’ chain growth

Question 7

When is DNA replication terminated?

Answer 7

When replication forks meet

Question 8

How is transcription initiated?

Answer 8

Recognition of the promoter region

Transcription initiation factors recruit rna polymerase

Question 9

How is transcription terminated?

Answer 9

Dependent on the sequence

Question 10

What are the promoter regions?

Answer 10

Signals that tell the transcription where to start

Question 11

What is the transcription unit?

Answer 11

The promoter region + the gene coding for the protein

Question 12

What does every promoter region contain?

Answer 12

A TATAAA box sequence in the 5’—>3’ direction

Question 13

How is transcription initiated?

Answer 13

Binding of transcription initiation factors to TATAAAA box of the promoter region —> recruitment of rna polymerase

Question 14

When does transcription begin?

Answer 14

The +1 point after RNA polymerase binds

Question 15

What does rna polymerase do during the elongation phase of transcription?

Answer 15

Unwinds 2 dna strands, reads template strand in 3’–>5 direction —> produces mRNA in the 5’—>3’ direction

Question 16

What are the two dna strands called in transcription?

Answer 16

Coding strand

Template strand

Question 17

What is the purpose of RNA processing? When does it happen?

Answer 17

To protect the mRNA

Happens immediately while mRNA is being made

Question 18

What are 3 different ways in which mRNA is processed?

Answer 18

Capping
Tailing (polyadenylation)
Splicing

Question 19

What is capping?

Answer 19

Cap created at the 5’ end to prevent against degradation - 5’-5’ linkage is created

Question 20

What is tailing/polyadenylation?

Answer 20

At the 3’ end, a polyA (200+ bases long) tail added to protect against degradation

Question 21

Which enzyme adds the polyA tail to mRNA?

Answer 21

PolyA polymerase

Question 22

What is splicing of an mRNA molecule?

Answer 22

Introns that do not code for the protein are spliced out by endocnucleases

Question 23

Ribosomes which exist freely in the cytoplasm usually form which shape? What is the structure called?

Answer 23

A spiral shape

Polysome

Question 24

What is the length of a prokaryotic ribosome? What type of ribosome exist in prokaryotes?

Answer 24

20nm

70S

Question 25

What is the length of a eukaryotic ribosome? What type of ribosomes exist in eukaryotes?

Answer 25

32nm 80S

Question 26

What does a 70S prokaryotic ribosome consist of?

Answer 26

2 sub units; 50S and 30S 3rRNAs + 56 proteins

Question 27

What does an 80S ribosome consist of?

Answer 27

2 sub units; 60S and 40S 4rRNAs + 82 proteins

Question 28

What are the majority of the proteins found in 70s and 80s ribosomes?

Answer 28

Enzymes for translation

Question 29

What are the three main types of RNA? By which enzyme are each of them produced?

Answer 29

``` Ribosomal RNA (rRNA) - RNA polymerase I Messenger RNA (mRNA) - RNA polymerase II Transfer RNA (tRNA) - RNA polymerase III ```

Question 30

The majority of RNA found in our cells is...

Answer 30

Ribosomal RNA

Question 31

There are around _____ different kinds of tRNA

Answer 31

~100 different kinds

Question 32

The genetic code is degenerate, what does this mean?

Answer 32

There are 20 amino acids and 64 different codons, this means that 1 amino acid can be coded for by more than 1 codon.

Question 33

What is the structure of a tRNA molecule?

Answer 33

Single stranded | Clover model

Question 34

What property of RNA allows tRNA to form this clover shape?

Answer 34

RNA is able to make stem loops, where hydrogen bonds are formed between anti-parallel complementary sequences

Question 35

Where does the amino acid bind to on a tRNA molecule?

Answer 35

At the 3' (-OH) end

Question 36

Proteins always begin with which amino acid?

Answer 36

AUG - methionine

Question 37

Translation is terminated by stop codons, what are the stop codons?

Answer 37

UAG, UGA, UAA

Question 38

Each tRNA contains a __________ anticodon to the amino acid it recruits

Answer 38

Complementary

Question 39

What bases exist at tRNA anticodons to allow the degeneracy/flexibility of the genetic code? What are bases at this position called?

Answer 39

I bases Wobble bases

Question 40

Which bases occupy the wobble base position on the codon and anticodon?

Answer 40

The 5' base of the anticodon | And the 3' base of the codon

Question 41

What happens at initiation during translation?

Answer 41

Methionine connected to tRNA binds to 5' cap of mRNA with the 40S sub unit of the ribosome Sub unit moves along until AUG codon found (energy required) Fully functional ribosome formed (energy required)

Question 42

A ribosome can recognise how many codons at one time? What two sites does a ribosome have?

Answer 42

2 A site and a P site

Question 43

Which enzyme helps with the formation of peptide bonds at ribosomes?

Answer 43

Peptidyl transferase

Question 44

What happens during the elongation stage of translation?

Answer 44

Binding of the complementary amino-acyl tRNA Peptide bond formed at the A site Uncharged tRNA at P site released from ribosome Translocation (using ATP), growing chain at P site, A site empty Process continues....

Question 45

When does termination occur in translation?

Answer 45

When a stop codon appears at A site

Question 46

What happens during termination in translation?

Answer 46

Stop codon appears at A site Bond between peptide and tRNA broken with H2O Leaves uncharged tRNA molecule and peptide Peptide released leaving empty ribosome

Question 47

What is the complex of proteins that splices out the introns in a pre-RNA molecule called?

Answer 47

Spliceosome

Question 48

In any mRNA molecule there are two UTR (untranslatable regions) - where are these found? What is the sequence between these two points called?

Answer 48

Before the initiation codon After the stop codon Open reading frame

Question 49

What are some features of translation in bacteria?

Answer 49

It is coupled with transcription Only one type of rna polymerase No post transcriptional modification

Question 50

Give an example of a drug affecting bacterial translation by affecting prokaryotic ribosomes?

Answer 50

Erythromycin - binds to the 50S ribosomal subunit Prevents translocation