Topic 3- stem cells Flashcards
stem cells
undifferentiated cells
keep dividing to give rise to other cell types
multipotent
give rise to many types of cell
pluripotent
give rise to many types of specialised cells- not placental
totipotent
give rise to all/ any types of specialised cells (incl placental)
ethical issues
embryonic- embryos killed in process
destroying potential life
risk of infection during implantation of stem cells- could become cancerous
differential gene expression
allows cells to become specialised
occurrance of differential gene expression
stimulus on unspecialised cells
activator and repressor molecules bind to promotor regions
active genes transcribed to produce RNA
mRNA translated on ribosomes used to produce protein
protein able to change structure and function of cells
phenotype
characteristics of an organism
result from interaction of genes of the organism with the environment
continuous variation
variation within a range
includes mass and height
discontinuous
can only take particular values
like gender and shoe size
monogenic
characteristics influenced by one gene only
polygenic inheritence
when several genes at different loci are involved in determining a characteristic
often gives rise to continuous variation
epigenetic modifications
modifications to DNA which do not change base sequence
modify the activation of certain genes
DNA methylation
process by which methyl groups are added to DNA
modifies function of DNA
usually suppresses gene transcription
change is permanent
histone modification
Acetylation- addition of acetyl group
activates chromatin
allows transcription
Methylation- addition of a methyl group- can cause activation/inactivation of chromatin
