Genome expression

Question 1

Cellular differentation

Answer 1

The process by which a cell changes from one type to another. This is a permanent change ( in mamals)
bijv. stem cell to neuron

Question 2

External stimuli

Answer 2

Can alter gene expression
bijv. growth factor or hormones
1. directly enter the cell
2. Interact with surface receptor

Question 3

Direct cell permeation

Answer 3

Lipophilic / hydrophobic compounds -> steroid hormones
- Freely diffuse through cell membrane
- Bind to cytosolic receptor in cell and migrate to nucleus
- The hormone-receptor complex acts as TF, binding to DNA hormone response element

Question 4

Kinase receptors

Answer 4

Transduction of signal is mediated by phosphorylation of cytoplasmic protein
3 main types:
1. tyrosine kinase receptors
2. serine-threonine kinase receptors
3. Kinase-associated receptors

Question 5

Tyrosine kinase receptors

Answer 5

• Phosphorylate a Tyr residue on the target protein
• Dimers of 2 identical subunits
• Extracellular domain for ligand binding
• Intracellular domain with kinase activity
• Dimers are dissociated -> interaction with the ligand promotes dimerization -> activating kinase activity.

Question 6

MAP kinase pathway

Answer 6

• an inactive G-protein (Ras bound to GDP) anchored to protein close to mitogen receptor
• Mitogen receptor dimerizes in response to mitogen binding
• Dimerization induces self-phosphorylation of the receptor and recruitment of GEF.
• GEF promotes exchange of GDP to GTP -> activitng the G-protein (Ras)
• Ras-GTP is now able to phosphorylate Raf
• Phosphorylated Raf phosphorylates Mek
• Mek now does the same to MAPK
• MAPK translocates to nucleus activating a series of TF (by phosphorylation)

Question 7

JAK/STAT pathway

Answer 7

• Receptor is associated with the Janus kinase (JAK)
• Interaction of the receptor with a ligand (usually cytokine) stimulates dimerization.
• 2 JAK kinase subunits are brought in close to each other by the receptor dimerization and phosphorylate each other.
• JAK is now active and can phosphorylate STATs
• STATs will now dimerize, allowing translocation to nucleus
• STAT dimer binds to DNA and activates transcription of a specific set of genes.

Question 8

Blastocyst

Answer 8

1. Trophoblast
2. Inner cell mass (ICM)

Question 9

Types of promoters of ESCs

Answer 9

1. H3K4me3
2. H3K27me3

Question 10

H3K4me3

Answer 10

Marks active promoters of genes that need to be actively transcribed by the cell

Question 11

H3K27me3

Answer 11

Marks repressed promoters of genes that must not be transcribed

Question 12

Bivalency

Answer 12

• present both marks (H3K4me3 and H3K27me3)
• Present in promoters of developmental genes in ESCs
• are not active, nor stably repressed.
• allows ESCs to rapidly activate/deactivate developmental genes as soon as they receive a differentiation stimulus