stem cells and totipotency Flashcards
define cell differentiation
the process by which cells develop into specialised cells
why does cell differentiation occur
no one cell can provide the best conditions for all functions. More efficient if they are adapted to their function
what role does cell differentiation have in gene expression
all cells derived from mitotic division of zygotes
contain all genes, therefore capable of making all proteins. Only certain genes are expressed (switched on) in any one cell at one time. Some genes are permanently expressed in all cells (like those that produce enzymes for respiration). Some genes permanently switched off in certain cells
once specialised can stem cells develop into other types of cells
most specialised cells can no longer develop into any type of cell
what is a stem cell
the only type of cells that can differentiate
self renewal - stem cells’ ability to divide and form an identical copy
define self renewal
stem cells’ ability to divide and form an identical copy
what are the 4 sources of stem cells in humans
embryonic stem cells
umbilical cord stem cells
placental stem cells
adult stem cells
what is an embryonic stem cell
from early stage of embryo development, can become any type of cell
what is an umbilical cord stem cell
from umbilical cord, similar to adult stem cells
what is an placental stem cell
in placenta, develop into specific types of cell
what is an adult stem cell
found in body tissues of all ages. Specific to particular tissue/organ and produce cells to maintain and repair tissue
what are totipotent cells
totipotent cells can develop into all types of cell
in early embryo (zygote) can develop into any type of cell
develops into a pluripotent cell
how do totipotent cells become specialised
during specialisation only some genes are expressed so the cell only makes the proteins it needs to carry out its specialised function. A variety of stimuli ensure that the genes that are not needed stay switched off.
how are genes prevented from being expressed in totipotent cells
prevent transcription and therefore production of mRNA
prevent translation
list the 4 types of stem cells
totipotent
pluripotent
multipotent
unipotent
describe what pluripotent cells are
in embryos
become almost any type of cell
e.g: embryonic and foetal stem cells
give 2 examples of pluripotent cells
embryonic and foetal stem cells
describe what multipotent cells are
in adults
differentiate into a limited number of specialised cells
e.g: bone marrow stem cells make blood cells, adult stem cells, umbilical cord stem cells
give 3 examples of multipotent cells
e.g: bone marrow stem cells make blood cells, adult stem cells, umbilical cord stem cells
describe what unipotent cells are
differentiate into a single type of cell
derived from multipotent cells and found in adult tissue
where are unipotent cells found
in adult tissue
explain the importance of iPS
type of pluripotent cell produced from unipotent cell (which could almost be any body cell). Body cell altered in lab to give it characteristics of an embryonic stem cell. Causes genes and transcriptional factors in the cell to be expressed that are normally switched off (shows the genes are still there just inactive). Same as embryonic in form and function, express same genes but not exact duplicates. Can self renew so limitless supply ideal for medical research and treatment and avoid ethical issues from use of embryonic stem cells
what are the uses of iPS
- disease pathophysiology
- identifying novel drug targets
- drug screening
describe some evidence that all cells contain all genes but they are “switched off” in some cells
ips - unipotent cells can be altered to act like pluripotent cells and produce the proteins of an embryonic stem cell
give examples of how pluripotent cells can be used in treating human disorders
- cells can be used to regrow tissues that have been damaged
- skin grafts for burns
- heart muscle cells for heart damage
- nerve cells for MS
- blood cells for leukaemia
- bone cells for osteoporosis
