Differentiation 2 - Regulation of Gene Transcription

Question 1

what are the 2 aspects of cell differentiation?

Answer 1

• cell specialisation - what makes a cell different
• cell behaviours during development - how cells become different

Question 2

What is TFIID?

Answer 2

Transcription factor II D

• recruits polymerase

Question 3

What is the role of the enhancer?

Answer 3

• it is signal sequences next to genes
• they are recognised by TFs - can be cell type specific
• can activate or repress RNA polymerase

Question 4

What is if a gene is transcribed dependent on?

Answer 4

• what binding sites are in its DNA enhancer sequences AND
• cheater appropriate TFs are present in the cell

Question 5

How do TFs activate transcription?

Answer 5

• recruit RNA polymerse directly to the TATA box or indirectly by:
  
  • histone acetyle transferase (HAT)
    
    • acetylation loosens DNA around histones, more accessible
  • chromatin-remodelling complex
    
    • making DNA more or less accessible

Question 6

Which germ layer forms the muscles?

Answer 6

mesoderm

Question 7

what are myoblasts?

Answer 7

precursors to muscle cells but are committed to becoming them

Question 8

How to myoblasts differentiate into muscle cells?

Answer 8

• they are not differentiated as they need to be in a large enough group
• they are secreting growth factor, keeping them proliferating
• eventually they stop producing growth factor
• they then leave the cell cycle and differentiate

Question 9

When do muscle specific proteins appear?

Answer 9

during cell fusion

Question 10

What is the role of MoyD?

Answer 10

• a TF
• homodimer
• basic-helix-loop-helix -> basic amino acids for DNA contact
• binds to the E box in the enhancer
• activates the expression of myosin II and evert muscle-specific gene
• represses some genes

Question 11

What is the effect of mutation MyoD?

Answer 11

cells have stalled development and do not differentiate

Question 12

can other cell precursors be forced to be muscles?

Answer 12

yes, if the expression of MyoD is introduced

Question 13

what are 3 methods for genetic analysis of TF function?

Answer 13

• expression function - where does it function?
• loss of function
• gain of function

Question 15

What does a Glabara 1 mutation do?

Answer 15

affects the gene coding for a TF for trichomes in arabidopsis

Question 16

how do TFs recognise their binding sites?

Answer 16

• there is a region in the protein that inserts itself into the major groove and contacts the bases

Question 17

do TFs work alone?

Answer 17

no, they work together
- it may be one or the other
- or both may be required

Question 18

How can TFs be repressors?

Answer 18

• prevent binding of activators
• recruit proteins that tighten chromatin, making the gene less accessible

Question 19

Where does the GATA 1 TF bind?

Answer 19

(A/T) GATA (A/G)

Question 20

What can mutations in GATA 1 lead to?

Answer 20

anemia due to death of erythroid precursor cells

Question 21

What are 4 target genes of GATA1?

Answer 21

• alpha and beta global
• erythropoietin receptor
• Haem biosynthesis enzymes
• spectrin

Question 22

explain the 5’ enhancers of the beta-globin gene

Answer 22

• gene will be activated if GATA1, CP1 and NF1 are all bound

Question 23

Why is more than GATA1 needed for transcription of beta-globing?

Answer 23

• GATA1 expressed in several blood lineages
• it only activates global genes in erythroblasts because of this combination