Gene regulation in eukaryotes

Question 1

if cells arent efficient with their energy, what will happen to them?

Answer 1

they will be outcompeteted and will die out

Question 2

why the need for gene regulation?

Answer 2

as with prokaryotes there is a need to be able to respond to cues from the environment – so that efficient use of energy resources, response to stressors and protection from attack can be regulated effectively.

Question 3

many eukaryotes are…

Answer 3

…complex multicellular organisms with highly differentiated cells

Question 4

What must cells go through in order to become differentiated?

Answer 4

complex developmental changes

Question 5

in order to become differentiated cells must go through complex developmental changes.

What do these changes necessitate?

Answer 5

different genes being turned on at the correct times to produce a mature cell which will have a different complement of proteins from its precursor and also from other types of differentiated cell

Question 6

What can a Haematopoietic stem cell differentiate into?

Answer 6

can differentiate into any kind of BLOOD cell. Can become a Common myeloid progenitor cells or common lymphoid progenitor cells.

Question 7

What do Haematopoietic stem cells require?

Answer 7

signals from the body, using receptors. These signals tell them what kind of signals the body needs.

Question 8

What needs to happen to hematopoietic stem cells in order to become different cells?

Answer 8

In order to become these different cells, different genes need to be turned on or turned off, and in the correct order. Without this, there are no differentiated cell types, no cell differentiation.

Question 9

eukaryotic genes are more complex than…

Answer 9

…those of prokaryotes.

Question 10

what is the open reading frame (ORF) composed of?

Answer 10

exons within the gene

Question 11

what is the open reading frame (ORF) split by?

Answer 11

intervening non-coding DNA in the form of introns (not always)

Question 12

what are introns?

Answer 12

intervening non-coding DNA

Question 13

in order to be expressed as a transcript from a eukaryotic, the gene has to be ….

Answer 13

… processed to remove the introns

Question 14

what do most eukaryotic cells have?

Answer 14

Most eukaryotic genes have exons and introns.

Question 15

what are the three types of RNA Polymerase?

Answer 15

RNA Polymerase I
RNA Polymerase II
RNA Polymerase III

Question 16

What does RNA Polymerase I do?

Answer 16

rRNA genes – the functional components of ribosomes

Question 17

What does RNA polymerase II do?

Answer 17

protein coding genes, miRNA, snRNA

Question 18

What does RNA polymerase III do?

Answer 18

tRNA, some rRNA, some snRNA

Question 19

How many types of RNA polymerase in eukaryotes?

Answer 19

3 types of rna polym in eukaryotes.

Question 20

What does transcription depends upon?

Answer 20

The formation of a preinitiation complex (PIC) comprising of basal transcription factors (TF).

Question 21

What do basal transcription factors consist of??

Answer 21

TFIIA, TFIIB, TFIIF, TFIIE, TFIIH, and TFIID.

Question 22

What is TFIID?

Answer 22

TFIID is a complex of different protein subunits including TATA Binding Protein.

Question 23

Where there is a TATA Box in the promoter this protein binds to….

Answer 23

…DNA at that point helping to recruit RNA polymerase II to the transcription start of a gene.

Question 24

the complexity of promoter elements varies…

Answer 24

…hugely in eukaryotes

Question 25

simple single-celled eukaryotes commonly have promoters that are…

Answer 25

…simple and proximal to the gene itself

Question 26

simple single-celled eukaryotes commonly have promoters that are simple and proximal to the gene itself whilst multicellular organisms may …

Answer 26

…have regulatory elements many kilobases away from the gene itself.

Question 27

What does the core promoter enable?

Answer 27

enables the transcription initiation complex to bind to the promoter.

Question 28

What does the core promoter have upstream?

Answer 28

have responsive elements upstream of the core promoter (up to several kilobases).

Question 29

What is the purpose of the responsive elements upstream of the core promoter?

Answer 29

proteins bind to these and either enhance of silence the genes by interacting with proteins in the transcription initiation complex.

Question 30

Cell-specific modules are specific to…

Answer 30

…certain cell types (cell specific).

Question 31

Purpose of Cell-specific modules ?

Answer 31

ensuring that gene expression only takes place in the correct cell.

Question 32

regulation can occur at…

Answer 32

…multiple points.

Question 33

Where does gene regulation occur?

Answer 33

1 - DNA unpacking/alteration (methylation, acetylation etc)

2 - regulation at the level of transcription

3 - regulation at the processing stage

4 - regulation of splicing to form different proteins

5 - post-transcriptional regulation – mRNA stability

6 - regulation of translation

7 - post-translational regulation (e.g. phosphorylation)

8 – protein stability

Question 34

when does elongation occur?

Answer 34

elongation occurs after transcription is initiated and the gene is transcribed by complementary base-paring of ribonucleotides to the template (non-coding) strand

Question 35

When does termination occur?

Answer 35

termination occurs after the polyadenylation signal is transcribed

Question 36

What happens after termination?

Answer 36

RNA polymerase dissociates from the DNA strand and the pre-mRNA

Question 37

unlike in bacterial genes regulation in eukaryotic genes may take place over …

Answer 37

… a large distance.

Question 38

DNA is…

Answer 38

…looped

Question 39

DNA is looped and activators and repressors connect their binding regions (enhancers and silencers) with …

Answer 39

…the transcription initiation complex via mediator proteins

Question 40

What are the binding regions of activators and repressors?

Answer 40

enhancers and silencers

Question 41

What must happen to eukaryotic transcripts before export to cytoplasm and translation?

Answer 41

unlike in prokaryotes – eukaryotic transcripts have to be processed before export to the cytoplasm and translation