Cell differentiation and gene expression Flashcards
What is differentiation?
The production of many cell types within an organism
What type of change is differentiation?
Stable, complex change
what is determination?
The stability of cell differentiation even after the end of any inducing signal
Is determination transmitted?
Determination is transmitted to daughter cells after division
What is cell lineage?
The series of cell types evolving from a zygote to a mature cell type
How does differentiation occur?
Occurs in steps
What occurs in each step in differentiation?
At each step an immature cell type such as a precursor changes into a more mature cell type and this still may be a type of precursor
What do branches represent?
Branches don’t represent cell division, just the possibilities of types of daughter cells that can be formed from precursor cells
What can particular precursors do?(pluripotent)
Particular precursors can divide into more than one daughter cell types
What do different cell types do?
Different cell types express different genes
What does the whole process of gene expression lead to the synthesis of?
• The whole process leading to the synthesis of the final product of the gene:
○ Protein
○ Functional RNAs
○ Include processes like transcription and translation
What is modulation?
Simple reversible change in gene expression, with no change in cell type
What is modulation also known as?
Adaptation
What type of change is modulation?
Temporary simple change
Differentiation vs modulation
Differentiation is stable and is a complex change whereas modulation is temporary and is a simple change
Both involve gene expression
How was dolly the sheep made?
- Differentiated mammary epithelial sheep cell fused into cytoplasm of sheep oocyte
- Fused cell divided many times and proliferated forming an embryo
- Put in the uterus of an ewe
- Embryo had all the genes for a whole sheep
Was dolly the sheep fertile?
Yes
what happens during one stage of lineage?
During one step of lineage, multiple genes that determine cell type are activated during expression while others are repressed
What is the program of differentiation?
Set of expressed genes in a given cell type
At What leverl is the program of differentiation controlled at?
Largely controlled during mRNA transcription
How is differential transcription detected?
Detected by using individual probes by RNA-seq
What does differential transcription reveal?
Reveals the difference in RNA between 2 cell types
What are the two main levels of control?
Chromatin remodeling and methylation
What does folding do in chromatin remodeling?
Folding interferes with transcription, as transcription machinery cannot access DNA
What do different cell types have in chromatin remodelling?
Different cell types have different sections of genome as heterochromatin
How is gene expression affected in different cell types during chromatin remodeling?
in different cell types, different parts of the genome are translated so gene expression varies
What does methylation do?
Increases heterochromatin
How does methylation work?
○ A methyl group binds to a cytosine(in a CpG) becoming methylcytosine
○ This is copied onto the opposite strand by maintenance methyl transferase
Where does methylation occur?
DNA methylation occurs in whole stretches rich in CpG pairs
What does methylation cause?
Methylation causes folding of chromatin
What happens to methylation patterns?
Methylation pattern is remembered in daughter cells
What is de nova methylation
§ CpG pairs are not always methylated
§ Unmethylated pairs can become methylated by a de novo methyltransferase
How are different genes activated?
Different genes are activated by different transcription factors
What do different cell types do?
Different cell types express different ranges of transcription factors
What happens to some genes?
Some genes are transcribed in nearly all cell types
What are master gene regulators?
A transcription factor that regulates transcription of a whole set of lineage specific genes, like a program
What cell divide very rarely to repair DNA damage?
Endothelium and liver cells
What is terminal differentiation?
Cells that cannot divide
What can happen to terminally differentiated cells?
Terminally differentiated cells can be replaced by precursors somatic stem cells
What is cancer not caused by?
Cancer is not caused by faulty differentiation
What is deficient in cancer cells?
Differentiation is deficient in cancer cells
What do tumor cells look like?
Look like precursors
What is aniridia?
Aniridia is the lack of the iris of the eye due to a mutation in the transcription factor PAX6
What is thrombocytopenia?
Thrombocytopenia is a platelet deficiency due to a mutation of GATA-1 which is needed for the differentiation of platelets.
