stem cells

Question 1

what are stem cells

Answer 1

undifferentiated cells that continually divide to become specialised.

Question 2

what is the process by which cells become specialised

Answer 2

differentiation

Question 3

totipotent stem cells

Answer 3

can differentiate into any type of cell
occur for a limited time in the mammalian embryo

Question 4

pluripotent stem cells

Answer 4

differentiate into almost any type of cell and can differentiate in unlimited numbers used to treat human disorders

Question 5

multipotent stem cells

Answer 5

found in mature adult body cells
divide to form a limited number of cells

Question 6

unipotent stem cells

Answer 6

found in mature adult body cells
divide to form one type of cell
used to make cardiomyocytes

Question 7

induced pluripotent stem cells (iPS)

Answer 7

produced from adult body cells
switch genes on and off to control transcription of genes
can be used to generate transplants without risk of immune rejection
an adult/somatic cell that has been treated with transcription factors to acquire pluripotent properties and the ability to differentiate into many cell types

Question 8

how do transcription factors work

Answer 8

proteins that enter the nucleus from the cytoplasm via nuclear pores
transcription factors are activated via a signalling pathway which usually starts from outside of the cell.
some transcription factors bind to a promoter region of a gene
this binding will allow or prevent the transcription of a gene from taking place

Question 9

how do transcription factors interact with RNA polymerase

Answer 9

assisting RNA polymerase binding to gene to stimulate gene expression or by preventing it from binding so inhibiting gene expression
therefore the presence of a transcription factor will either increase or decrease the rate of transcription of a gene.

Question 10

use of embryonic stem cells

Answer 10

• banned for use in research in many countries because they are considered unethical because the embryo cannot consent to use
• in some countries they can be used but only totipotent and pluripotent if used within 5 days of fertillisation- embryos used are specifically donated for research and fertillised in vitro

Question 11

multipotent adult stem cells use

Answer 11

only able to produce limited range of cell types
found in certain tissues in body such as bone marrow used to form blood cells and brain
research is being carried out on stem cell therapy which uses adult stem cells to treat diseases by introducing it to damaged tissue