3C Differentiation and variation Flashcards
What is a stem cell
An undifferentiated cell that is able to specialise
Totipotent- differentiate into any cell in an organism
pluripotent- produce most specialised cells in an organism
Transcription factors
Proteins that bind to DNA and activate or deactivate genes by increasing or decreasing rate of transcription.
They bind to the start of genes in eukaryotes and to operons in prokaryotes
What is an operon
a section of DNA containing a cluster of structural genes that are transcribed together
Lac operon
When lactose is not present: regulatory gene produces the repressor which binds to the operator region, blocking RNA polymerase from binding to promotor region
When lactose is present: lactose binds to the repressor, changing its shape so it cannot bind to the operator site. RNA polymerase can bind to the promotor region and transcribe the genes to produce enzymes
Stem cell uses
medicine: replace damaged tissue including nerve tissue for paralysis or cardiac tissue for heart disease
Improves quality of life
Save lives by growing organs for transplant
Adult vs embryonic stem cells
Adult: body tissues eg bone marrow
little risk
already differentiated- limited range of cells
using their own stem cells means less risk of rejection
embryonic: early embryos created using IVF
can develop into all types of specialised cells
can be rejected by the body
Ethical issues of embryonic stem cells
Destruction of a viable embryo viewed as having a right to life
less issues with stem cells artificially stimulated to divide as they couldn’t survive past a few days
Regulations in stem cell research/use
Licensing and training research centres to ensure fully trained staff understand research implications and embryos aren’t wasted
Producing guidelines to ensure scientists use acceptable sources of stem cells and controlled extraction methods
authorities look at research proposals to ensure research is not unnecessarily repeated/ is carried out with good reason
continuous vs discontinuous variation
continuous- vary in a range, no distinct categories
discontinuous- distinct categories where an individual will only fall into one category
Epigenetic factors
Histone modification: removal of acetyl groups means chromatin becomes highly condensed and genes in the DNA cant be transcribed as RNA polymerase cannot bind, repressing the gene.
