Cell biology - Cell division Flashcards
what are chromosomes
- they are coiled up lengths of DNA molecules
- carry large number of genes
what are genes
parts of chromosomes that control the development of different characteristics such as hair colour
how many pairs of chromosomes are in a single cell
23, there are 46 all together
why is the cell cycle beneficial
- allows for the growth, repair and asexual reproduction of cells
what is the stage of the cell cycle where the cell divides
mitosis
what do multicellular organisms use mitosis for
to grow or replace damaged cells
what does the end of the cell cycle result inn
- two new cells which are identical to the original cell, with the same number of chromosomes
describe the initial growth stage
- the cell grows and increases the amount of subcellular structures such as mitochondria and ribosomes
- chromosomes double and line up in the middle of the cel; both “arms” of the chromosome are identical
summarise mitosis
- Cell grows and increases number of subcellular structures such as mitochondria and ribosomes
- cell duplicates it’s DNA. The DNA is copied and forms X shaped chromosomes
3. The chromosomes line up at the centre and get pulled apart by cell fibres, Each arm of the chromosome go to opposite ends of the cell
5. Cytoplasm and cell membrane divide
6. Cell had now produced two new identical daughter cells
what is mitosis
a type of cell division which produces daughter cells identical to the parent
Length of time in phase
observed number of cells at the stage / total number of cells observed x total length of time cycle
what is binary fission
how prokaryotic cells divide into two / replicate
describe the steps of binary fission
1- the circular DNA and plasmids replicate
2 - the cell gets bigger and the DNA strands move to opposite ends of the cell
3- cytoplasm begins to divide, new cell walls begin to form
4- cytoplasm divides and two daughter cells are produced, each having one copy of the circular DNA, but having a variable number of copies of the plasmids
what are stem cells
undifferentiated cells which can divide and differentiate into different kinds of cells, depending on what instruction they are given
where are stem cells found ( humans )
- in early human embryos, have potential to turn into any kind of cell at all
- also in adults, only certain places though like bone marrow,and unlike embryonic cells, cannot turn into any type of cell, only certain ones like blood cells
stem cell uses
- therapeutic cloning, where embryo could be made to have the same genetic info as the patient
- curing things such as diabetes, spinal injuries,
where are stem cells found in plants
in the meristems ( where growth occurs )
whats the difference between adult human stem cells and adult plant stem cells
unlike a human adult stem cell, throughout a plants entire life, cells in the meristem can differentiate into any type of plant cell, not restricted
risks of stem cell
- difficult to find suitable stem cell donors
- stem cells grown in a lab could be contaminated with a virus which could passed on to patient and make them sick
- the donor has to be compatible with the patients or else WBC produced by the donated bone marrow could attack the patients body
- no guarantee how successful these therapies will be
ethical issues with stem cell
- human embryos being used for experiments goes against many religious beliefs ( sanctity of life )
- does the embryo have rights?
- For therapeutic cloning is it right to create embryos for therapy, and destroy them in the process?
social issues with stem cell
educating the public about what stem cells can, and can’t do, is important
- talk about whether the benefits outweigh the risks
advantages of stem cells
- embryonic stem cells can be used to replace faulty cells in sick people, e.g you could make insulin producing cells for people with diabetes
- therepeutic cloning, an embryo is made with the same genetic info as patient, meaning the body won’t reject it
what is the importance of mitosis in unicellular organisms
for asexual reproduction
how can stem cells be used for bone marrow transplants
- leukaemia is a cancer if the bone marrow
- to treat it, the patients existing bone marrow is destroyed using radiation
- patient then receives a transplant of bone marrow from a donor
- the stem cells in the bone marrow now divide and form new bone marrow. they also differentiate and form blood cells
why might we clone a plant?
- to stop it going extinct
- to increase yield for farmers
- cheap
