B2- Cell division Flashcards
What do we find in the nucleus ?
-In the nucleus we find chromosomes , which are made of hte molecule DNA .
How many chromosomes in a human ?
-Body cells contain two of each chromosome , they ar paired .
-Human body cells contain 23 pirs of chromosomes .
Chromosomes carry a large number of genes -determine our featrues .
Cells have to e able to divide - process known as ?
Cell Cyle
Mitosis division
What is the first stage of mitosis ?
Cell grows in size and mass and chromsoomes are replicated . (s1) INTERPHASE
-The nuclear membrane breaks down .9(s2) ALL MITOSIS
-Chromosomomes align acoss cenrer os cell .(s2)
One copy of each chromsome moves to opposite end of cell (s2)
nuclear ememrabne forms . (s2)
cell memrbane and cytoplasm divide (S3) CYTOKENSIS
What is the second stage of mitosis ?
-One set of chromosomes is pulled to ehch end of the cell .
The nucleus also divides .
What is the final stage of mitosis ?
-The cytoplasm and cell membrane divide to form tw identical cells .
What is one function of mitosis ?
-Mitosis is essentia for growth and development of multicelluar orgaisms (plants and animlas ).
What is the second function of mitosis ?
-Mmitosis takes place when an organism repairs itself (broken bone healing) .
What is the third function of mitosis ?
Mitosis happens during asexual reporduction .
Where can you specialise cells into anything in humans ?
When sperm and egg fuse during ferrtilisation , vum undergoes mitosis until ball of cells known as EMBRYO forms . Overtime , these cells undergo mitois and egin to form specialsied cells like nerve cells .
What is differentiation?
when cells specialise .
Early stage embryo ;
Have not differentaited . Any cell is capable oof differentating into ny tpe of body cell . Scientists call these EMBRYONIC STEM CELLS .
What is a stem cell
A stem cell is an undfferentiateed cell which can give rise to more cells of the same type and cn differentaie to form other type of cells .
Where can stem cells be found in an adult organism ?
Bone marrow , stem cells can differentaite to form cells found in our blood .
Differrence between adult and embryonic sem cells ?
Unlike embryonic stem cells , adult cells can’t differentate into any other type of cell .
Example of stem cells use in medicine .
- Bone marrow transport
- Leukaemia is a cancer o the bone marrow .
FIrst stage of bone marrow Transplant -for Leukaemia
-To treat Leukaemia , the patients existing bone marow is destroyed using radiation .
Second stage of bone marrow transplant
-The patiennt then receives a transplant of bone marrow from a doctor .
Third stage of a bone marrow transplant .
-Stem cells in the bone marrow now divide to form new bone marrow . They can also differerntiate and form blood cells .
Problem with bone marrow Transplants (1) .
-The donor has to be compatible with the patient . Otherwise white blood cells produced by the donte bone marrow could attack the pateints body .
Problem with bone marrow transpalnts (2)
-There is a risk that viruses can be apssed from the donor to the pateint .
Another way , stem cells can be used in medicne .
Therapeutic Cloning :
-Ane mebryo is produced with the same geens as the patient .
Stage one of therapeutic cloning ;
-Stem cells from the embryo can be transplanted into a patient without being rejected by the patient’s immune sytem .
Stage two of therapeutic cloning :
Once isnide the patient , the stem cells can differentiate , to replcase cells which have stopped working correctly .
This techinique can be used for diabaates or paralysis .
-However , some have ehtical and religious obections to this process .
Use of stem cells in plants ?
-Roots and buds contain meristemtissue . These stem cells can differnetaite into any type of plant tissue at any point in the life of a plant .
What can we use meristem tissue for ?
- To clone a rare plnt to stop it going extinct , or we could produce a cloned crop plant for farmers e,g disease resistant plants .
- RThis is quick and cheap
problem with embryonic stem cells .
- come from aborted embryos , spare embros , donated as they not toehrwise be used . Some say the use of potentail human beign a source orf cells or cure to others ?
- As embryo cannot give permsssion , using ir is a violation of human rights .
therapies mebryo problem
-expensive
diffiicult hard ot control .
Only been working for past 20 , difficult to persuade embryonic stem cells to differentiate into clels needed to reat pateints .
-viruses use bone marro stuff .
-money wasted on it , lot of investemnt can be used for other things .
