Understanding:
• Specialised tissues can develop by cell differentiation in multicellular organisms
• Differentiation involves the expression of some genes and not others in a cell’s genome
Differentiation
Differentiation is the process during development whereby newly formed cells become more specialised and distinct from one another as they mature
All cells of an organism share an identical genome – each cell contains the entire set of genetic instructions for that organism
The activation of different instructions (genes) within a given cell by chemical signals will cause it to differentiate
Cell Specialisation via Differential Gene Expression
Gene Packaging
Within the nucleus of a eukaryotic cell, DNA is packaged with proteins to form chromatin
- Active genes are usually packaged in an expanded form called euchromatin that is accessible to transcriptional machinery
- Inactive genes are typically packaged in a more condensed form called heterochromatin (saves space, not transcribed)
Differentiated cells will have different regions of DNA packaged as euchromatin and heterochromatin according to their specific function
Euchromatin versus Heterochromatin
