7.3 Stem Cells Flashcards
define totipotent
has the potential to form all 216 different cell types needed for a human
is a zygote totipotent, pluripotent or multipotent
totipotent
is a blastocyst totipotent, pluripotent or multipotent
pluripotent
how many days after fertilisation is a blastocyst formed
4 days
define pluripotent
some of the genes are switched off but lots are still switched on so can form all cell types needed in future
what are the 3 types of natural stem cells
totipotent
multipotent
pluripotent
define multipotent
can differentiate when needed to form some specialised cells but not all
what is another name for adult stem cells
somatic stem cells
what kind of cells can adult bone marrow stem cells differentiate
blood cells
where are umbilical cord stem cells found
in blood that drains from the placenta and umbilical cord is rich in pluripotent stem cells
what kind of animals were tested on to test hypothesis for cell determination
frogs and fruit flies
what did the early embryo in the cell determination experiment consist of
cells that are determined to produce skin cells as well as cells that are determined to produce brain cells
what was the hypothesis of the cell determination experiment
cell determination occurs irreversibly early after fertilisation
describe experiment one of the cell determination experiment
in the early embryo, the potential skin cells are taken and mixed with potential brain cells
the donor skin cells turned into brain cells
describe experiment two of the cell determination experiment
in an older embryo, the potential skin cells are taken and mixed with potential brain cells
this time, the donor skin cells remain as skin cells
do the experiments conducted in the cell determination experiment approve or disprove the hypothesis
the experiments disprove the hypothesis
what do cell determination and specialisation occur due to
the control of gene expression e.g transcription factors, epigenetics
as development of organism progresses, what happened to the genes
more genes are silenced
what is the structure of human haemoglobin
contains 2 alpha and 2 beta polypeptide chains
what is the structure of human fetal haemoglobin
contains 2 alpha and 2 gamma polypeptide chains so it has a higher affinity to oxygen
describe how a globin gene is turned into a globin polypeptide
globin gene is transcribed into mRNA and then translated into a globin polypeptide
what does epigenetics do
they change the proteins that the cell makes
what are the three methods of using stem cells
stemm cell therapy
therapeutic cloning
induced pluripotent stem cells
what can we use stem cells to do
produce cells
replace damaged or non-functional cells
describe the process of stem cell therapy
bone marrow cells from donor are given to a recipient with blood cancer
the stem cells then differentiate to produce normal blood cells
give some disadvantages of stem cell therapy
- difficult to control differentiation
- can cure patient but may develop cancer
- ethical issues
- risk of rejection
give some advantages of stem cell therapy
- used to make new body parts
- no rejection as cells come from own body
- research about replacing damaged heart cells after heart attack
what is therapeutic cloning
using stem cells to produce a large quantity of a specific tissue
describe the process of therapeutic cloning
- take out nucleus from cell of a male person with illness and fuse with egg from healthy female
- this produces pre-embryonic cell containing ill person’s DNA that will divide to give multiple cells
- the stem cells are removed and made to differentiate into required tissue type
4 in a person with type 1 diabetes, stem cells develop into beta cells of islet of Langerhans of pancreas, which produce insulin
what hormone converts glucose to glycogen
insulin
what hormone converts glycogen to glucose
glucagon
what happens in pancreas when blood concentration is too low
the alpha cells secrete glucagon
what happens in pancreas when blood concentration is too high
beta cells secrete insulin
what is damaged in type 1 diabetes
beta cells are damaged so they secrete little to no insulin
what are iPS cells
induced pluripotent stem cells
summarise how pluripotent stem cells can be formed
adult differentiated cell, eg skin cells, can genetically engineered into pluripotent cells using viruses
describe fully how pluripotent stem cells can be formed
- virus infects adult differentiated cell
- virus carries genes that code for transcription factors e.g Oct 3, Oct 4, Socks family
- genes are transcribed and translated to produce transcription factors
- transcription factors activate or inactivate genes in cell making it pluripotent
give an advantage of iPS cells
removes ethical issues
give disadvantages of iPS cells
- difficult to carry out
- leads to cancer development
- not identical to human embryonic stem cells
