Cell Differentiation and Epigenetics

Question 1

Define;
Induction
Competence
Specification
Morphogen

Answer 1

Induction: Process by which one group of cells influences the fate of another group through signals.

Competence: The ability of a cell to respond to inductive signals.

Specification: The initial stage of cell fate determination, reversible.

Morphogen: A signaling molecule that regulates cell fate in a concentration-dependent manner.

Question 2

What are the different classes of morphogens ?

Answer 2

Growth Factors (e.g., BMPs, Wnts, Hedgehog, FGF)
Cytokines
Steroid Hormones
Small Molecule Signals (e.g., retinoic acid)

Question 3

Describe epigenetic programming:

Answer 3

Chemical basis;
DNA Methylation: Addition of methyl groups (via DNMT enzymes) to CpG islands, silencing genes.

Histone modification;
Methylation: Can activate or repress transcription based on the site (e.g., H3K4me vs. H3K27me).
Acetylation: Generally associated with active chromatin and transcription.
Phosphorylation and Ubiquitination: Additional regulatory modifications

Question 4

What are the mechanisms of cell fate and determination ?

Answer 4

Epigenetic marks are heritable through cell divisions.
Chromatin structure and associated protein complexes maintain transcriptional states.
Positive feedback loops reinforce specific gene expression patterns.

Question 5

Describe gene silencing:

Answer 5

DNA Methylation: Methylation of promoter regions prevents transcription factor binding and recruits silencing complexes.
Histone Modification:
Methylation of histones (e.g., H3K9me, H3K27me) leads to chromatin compaction.
Works synergistically with DNA methylation to enforce gene silencing.