Gene expression in cell differentiation

Question 1

what are the major regulators of gene expression?

Answer 1

• transcription factors

Question 2

how is it clear that the expression of developmental genes is under tight control?

Answer 2

• the intricate coordination of various genetic, epigenetic, and signalling mechanisms

Question 3

what is the promoter region of a gene? (3)

Answer 3

• a stretch of DNA very close to the transcription start site
• facilitates the initation of transcription
• contains binding site for RNA polymerase, the enzyme responsible for transcribing the gene
  *

Question 4

what is the eve gene in drosophila? (2)

Answer 4

• refers to the well-known homeobox gene in drosophila
• plays a crucial role in early embryonic development, particuarly the segmented body plan

Question 5

what is the importance of the eve gene in gene expression?

Answer 5

• illustrates how genes can be swithed on and off near neighbours

Question 6

how many activator and repressor proteins work in the eve stripe?

Answer 6

• two of each
• combinations of TFs allow the prodution of very specific spatial and temporal outputs

Question 7

what is a cis-regulatory DNA sequence?

Answer 7

• an ‘umbrella term’ for all the bits of DNA that sit around genes to control their expression

Question 8

what are the small set of conserved signalling pathways that are used to control development? (5)

Answer 8

• notch
• Wnt
• Hedgehog
• TGF beta family
• RTK family

Question 9

what is the Y-secretase complex responsible for in the notch signalling pathway?

Answer 9

• cleaving the intracellular domain of the notch receptor, releasing it from the cell membrane

Question 10

what is the role of MAML proteins in the notch signalling pathway?

Answer 10

• helps promote transcription of target genes

Question 11

what is contact dependent signalling also known as?

Answer 11

• juxtacrine signalling

Question 12

what is the Wnt signalling pathway also known as?

Answer 12

• the canonical Beta Catenin pathway

Question 13

what pathway is the RTK signalling pathway very similar to and why?

Answer 13

• the TGf beta-family
• they both involve lots of phosphorylations

Question 14

what is a kinase cascade? (3)

Answer 14

• one protein phosphorylates another, which phosphorylates another etc
• phosphorylations occur until the last one does something else
• the last one is clalled the map kinase cascade

Question 15

how is the pattern of Hox gene expression set up?

Answer 15

• by transient signals

Question 16

polycomb vs trithorax proteins

Answer 16

polycomb - group of proteins that repress hox gene expression
trithorax - group of proteins that maintain expression of hox genes

Question 17

what is a nucleosome? (2)

Answer 17

• a segment of DNA wound around a histone protein core
• essentially tightly packed DNA

Question 18

how many histones are required for the assembly of the nucleosome in order for the DNA to fit into the nucleus of a cell?

Answer 18

• 8

Question 18

what is epigenetic inheritance? (2)

Answer 18

• heritable alteration in phenotype
• that does not come fom a change in DNA sequence

Question 19

what percentage of proteins in chromatin are histone proteins

Answer 19

50 %

Question 19

how the histone and DNA are connected? (3)

Answer 19

extensive interface between them involving:
* hydrogen bonds
* hydrophobic interactions
* salt linakges

Question 19

do TFs and chromatin structure ever meet, interlink in terms of gene expression

Answer 19

yes - TFs often direct local alterations in chromatin structure