The ability of cells to develop into various cell types
4 Different levels of potential (i.e. types of stem cells)?
Totipotent: can make all tissues and cell types AND extraembryonic tissues (zygote, blastomere in 4-cell embryo)
Pluripotent: can make all cell types BUT NOT extraembryonic tissue (ICM, emb. stem cells, iPS)
Multipotent: can make several cell types
Unipotent: can make only one cell type
Specification vs. determination? Which is reversible?
Specification: cell acquires bias towards a particular fate from neutral environment (reversible)
Determination: cell fate cannot be reversed from non-neutral environment
2 general mechanisms of fate specification?
: cell fate depends on determinants inherited from cell divisions (non-regulative)
- Conditional specification: neighbor decide your fate (regulative, i.e. early during development the embryo can replace missing cells)
Which type of fate specification is mammalian development?
When differentiating, genes are NOT lost...only the ones you need are expressed
5 mechanisms to regulate gene expression?
- 1. transcription
- 2. splicing
- 3. export of processed mRNA
- 4. translation/mRNA half-life
- 5. post-translational modifications
Patterns of gene expression in vivo?
Spatial patterns (every cell type, tissue-specific, organ-specific, cell-type)
Tempeoral patterns (constitutive, and modulated [i.e. inducible, repressible, rhythmic, circadian])
What is context-dependent gene expression?
a gene that is re-expressed at a different time may have a similar, different, or opposite function form when it was initially expressed
Definition of epigenetics?
heritable states of gene expression without underlying alterations in DNA seq.
4 epigenetic mechanisms?
imprinting - genes where only one allele is expressed and the other has been methylated (silenced)
gene silenceing - repression of gene
reprogramming- removing of epigenetic marks
X-chromosome inactivation - regulation of X chromosome during dosage compensation
Because girls have two X chromosomes...one is inactivated (dosage compensation). However 25% of the inactivated X chromosome is transcriptionally active.