3C Flashcards
What is a stem cell?
An unspecialised cell with ability to differentiate to become specialised
What is meant by totipotent stem cells?
Totipotent = can develop into any cell type including the placenta and embryonic cells.
What is meant by pluripotent stem cells?
Pluripotent = can develop into any cell type excluding the placental cells.
Through what process do stem cells become specialised?
Differential genne expression
Outline differential gene expression
Chemical stimuli activate certain genes and others are inactivated; the activated genes are transcribed and mRNA is formed; the mRNA is translated into proteins and those proteins alter the structure and function of a cell
What is a transcription factor?
A protein that can control the expression of genes
How does an activator work?
Binds to a site just before the gene. Helps RNA polymerase to bind and transcription occur.
How does a repressor work?
Binds to a site just before a gene. Prevents RNA polymerase from binding.
What is an operon made up of?
Structural genes, control elements and regulatory gene
What are the structural genes in an operon?
Genes that code for useful proteins (e.g. enzymes)
What are the control elements in an operon?
Include a promoter that RNA polymerase binds to and an operator that transcription factors bind to.
What is the regulatory genen in an operon?
Enzymes that repire lactose
What do the structural genes in the lac operon code for?
Regulatory gene produces lac repressor that binds to operator, RNA polymerase prevented from binding, lacZ, lacY and lacA not transcribed
Outline the function of the lac operon when glucose is present
Lactose binds to repressor changing its shape so that it can no longer bind to the operator, RNA polymerase can bind, lacZ, lacY and lacA transcribed and enzymes needed to respire lactose are produced
Outline the function of the lac operon when glucose is not present but lactose is
Give some uses of stem cells.
“● Treat diseases, such as Parkinson’s and multiple sclerosis.
● Replace damaged tissues, such as spinal cords.”
Why is use of stem cells controversial?
“● Involves killing embryos.
● There is a risk of infection after transplant due to immunosupressants.”
Define continuous variation
When individuals within a population vary within a range
Give two examples of continuous variation
Height and weight
Define discontinuous variation
Variation that falls into two or more distinct categories
Give an example of discontinuous variation
Blood type
Define phenotype.
The expression of an organism’s genes, combined with its interaction with the environment.
Define monogenic
A characteristic that is controlled by one gene at one locus, tend to display discontinuous variation
Define polygenic
A characteristic that is controlled by many genes at different loci, tend to display continuous variation
