Stem cells and totipotency Flashcards
Totipotent stem cells
-Found in early embryos
-Can differentiate into any cell type
Pluripotent stem cells
-Found in embryos
-Can differentiate into almost any type of cell
Multipotent stem cells
-Found in adults
-Can differentiate into a limited number of cells
Unipotent stem cells
-Made in adult tissue
-Derived from multipotent stem cells
-Can only differentiate into a single type of cell
Induced pluripotent stem cells (iPS cells)
-Can be genetically altered by turning on genes, giving them characteristics of pluripotent stem sells
-Are capable of self-renewal, so can replace embryonic stem cells in medical research and treatment
-Avoiding the ethical issues of using embryos
When iPS cells can be used
-Skin cells-burns & wounds
-Bone cells-osteoporosis
How do transcription factors work
-Each transcription factor has a DNA binding site that is specific to the promoter region of a pareticlar gene
-Where it binds, transcription begins, becuase it helps RNA polymerease to bind
-This produced pre-mRNA which is spliced and translated into a protein
Why genes are not expressed
The genes complementary transcription factor DNA binding site is BLOCKED by an inhibitor molecule
The role of oestrogen in initiating transcription
-Mammalian steroid hormone
-Oestrogen is small and lipid soluble. So can diffuse through the plasma membrane of cells
RNAi
-Gene expression is prevented by breaking down mRNA before it is translated into a protein
-RNAi is a small molecule of double-stranded RNA
Using RNAi to prevent gene expression
-Large double-stranded molecules are cut into RNAi by enzymes
-RNAi splits into single-stranded molecules, of which one, associated with a different enzyme
-RNAI guides this enzyme to a mRNA molecule
-Once the enzyme cuts the mRNA into small sections
-This makes the mRNA useless as translation cant occur
