Gene Regulation and Protein Synthesis

Question 1

Central Dogma

Answer 1

Flow of genetic information from DNA towards protein

Question 2

Location of Gene expression in Prokaryotes and Eukaryotes

Answer 2

Prokaryotes - within cytoplasm
Eukaryotes - from nucleus to cytoplasm

Question 3

Codon-Anticodon Base Pairing

Answer 3

tRNA anticodons form base pairs with mRNA codons
3 nucleotides - triplet

Question 4

Reading frames

Answer 4

How a nucleotide sequence is divided up.
Can be read in different ways, hence giving different amino acids
Depends on translation start site

Question 5

Translation Components (7)

Answer 5

Amino acids
tRNAs
Aminoacyl-tRNA-synthetases
Protein factors
Energy source - ATP/GTP
Ribosome (large and small subunits)
mRNA

Question 6

Aminoacyl-tRNA synthetases

Answer 6

Bind amino acids to specific tRNA using ATP

Question 7

Ribosomes - Subunits, Binding sites

Answer 7

4 rRNA molecules and protein components
3 binding sites (EPA)

Question 8

Initiation - Translation

Answer 8

Requires initiation factors
GTP hydrolysed
Small ribosomal subunit binds to 5’ mRNA end
Start codon - methionine
Large subunit joins assembly and initiator tRNA is located in P site

Question 9

Elongation - Translation

Answer 9

Elongation factor (EF-1a) brings next aminoacyl-tRNA to the A site
GTP hydrolysed, EF released from tRNA
Second elongation factor regenerates EF-1a

Question 10

Termination - Translation

Answer 10

Stop codon (UAA, UAG, UGA
No aminoacyl-tRNA base pairs with stop codon
Release factor binds stop codon
FInished protein cleaved off tRNA
Dissociation of RNA molecules (3)

Question 11

Peptide bond formation and translocation

Answer 11

Peptidyl transferase catalyses peptide bond formation between amino acids in P and A sites
EF-2 moves ribosome along mRNA
Empty tRNA moves to E site
tRNA with growing peptide moves from A to P site
A site is free

Question 12

Polysome

Answer 12

Multiple regions of translation

Question 13

Types of Mutations (5)

Answer 13

Point mutation - change single base

Missense mutation - change in amino acid sequence, change function

Nonsense mutation - new termination codon, change protein length

Silent mutation - no change in amino acid sequence, due to degeneracy, no effect on function

Frameshift mutation - addition/deletion of single base, change reading frame

Question 14

Chromosomal Mutations (4)

Answer 14

Deletions
Duplications
Inversions
Translocations

Question 15

What happens with the finished protein? (3)

Answer 15

Targeting
Modification
Degradation

Question 16

Free and Bound Ribosomes

Answer 16

Free Ribosome - cytosol, proteins destined for cytosol, nucleus, mitochondria, translocated post-transitionally

Bound RIbosomes - rough ER, proteins destined for membrane, ER, Golgi, secretion, translocated co-translationally

Question 17

Post-Translational Modifications

Answer 17

Phosphorylation
Acetylation
Methylation
Glycosylation
Disulphide bridges
Ubiquitinylation

Question 18

BREAK

Question 19

RNA

Answer 19

Single stranded
Stem loops sometimes
3 classes - rRNA, tRNA, mRNA

Question 20

tRNA

Answer 20

Adapters between nucleic acid code and amino acid code
Anticodon
Attach to 3’ end
Cloverleaf structure

Question 21

mRNA

Question 22

tRNA

Question 23

Transcription

Answer 23

RNA polymerase binding
DNA chain separation
Transcription initiation
Elongation
Termination

Question 24

Promoters

Answer 24

RNA Polymerase II specific promoter
Transcription = +1
TATA box = -25

Question 25

TATA box binding protein

Answer 25

Recognises TATA box Complex with TFIID (general TF) Introduces kink into DNA - determines transcriptional start and direction

Question 26

Initiation - Transcription

Answer 26

Additional general TFs Ordered - TFIID/TBP --> TFIIB --> TFIIF + RNA Pol I --> TFIIE + TFIIH RNA Pol II & TFIIF extend transcript on their own TFIID remains at pronoter

Question 27

Elongation - Transcription

Answer 27

Transcription bubble - one direction DNA unwound and rewound behind RNA Pol II 5' to 3' Complementary to template

Question 28

Termination - Transcription

Answer 28

Newly synthesised RNA makes stem-loop structure - followed by Us RNA cleavage

Question 29

Specific Regulation of Transcription

Answer 29

Specific TFs --> DNA-binding proteins (2 functional domains) Enhancers & Silencers - long stretches of DNA between binding site and transcription complex

Question 30

Coordinated Gene Expression

Answer 30

Specific stimuli Regulatory protein Bind to Response elements of multiple genes Produce different proteins

Question 31

Steroid Receptors

Answer 31

Family of TFs Domains - DNA-binding and ligand-binding Ligand binding --> Move to nucleus --> Bind to SREs

Question 32

Glucocorticoid Receptor

Answer 32

Steroids transported in blood Free steroids bind to steroid receptor --> Receptor translocates to nucleus --> Binds to response elements --> Coordination regulation

Question 33

Exons and Introns

Answer 33

Exons = Coding Regions Introns = Non-coding Regions Transcribed together Introns removed (splicing)

Question 34

Ends of mRNAs

Answer 34

5'cap Poly(A) tail