Cell division Flashcards
What does a nucleus contain?
Chromosomes
How many pairs of chromosomes are in a human nucleus?
23
What does a chromosome contain?
Many genes
What is a gene?
the code to make different proteins and control the development of different characteristics
What are chromosomes made up of?
DNA
What is mitosis?
single cell divides into two identical daughter cells
Examples of some cells that divide by mitosis
- hair and nail cells
- skin cells
- red and white blood cells
what are the steps of Mitosis
1) DNA replicates to form two copies of each chromosome
2) the membrane around the nucleus breaks down, the chromosomes condense and move freely in the cytoplasm
3) the chromosomes line up in the middle of the cell (equator)
4) the cell pulls apart the chromosomes into 2 arms. these are pulled to separated ends of the cell
5) the membrane forms around the sets of chromosomes on either ends of the cell. This forms 2 nuclei
6) the cytoplasm and cell membrane divide. The cell has non-identical 2 new daughter cells
what are the steps of the cell cycle?
1) each cell grows and makes new subcellular structures
2) DNA is copied and new chromosomes are made
3) mitosis
What are stem cells?
Unspecialised cells that can change to different types of cells
Where are stem cells found? - animals
Human embryos and adult bone marrow
the umbilical cord of a newborn baby
What can stem cells be used to treat?
Paralysis and diabetes
- treating conditions where cells are damaged or not working properly
- used to replace damaged cells
Where are stem cells found? - plants
Meristems of plants
Advantages of stem cells?
- They can be taken without hurting
- Will provide vital clues about how tissues develop
- Could treat Parkinson’s, Alzheimer’s, heart disease, strokes, arthritis, burns etc
- replace faulty cells
Disadvantages of stem cells?
- Use of embryos is unethical
- Embryonic stem cell research = murder
- Immune system might recognise stem cells as foreign and be rejected and die
- transfer of viral infections
What are embryonic stem cells?
stem cells from human embryos that can make all types of cells
what is therapeutic cloning?
A cloned embryo of the patient may be made and used as a source of stem cells
Why is therapeutic cloning beneficial?
the stem cells from the cloned embryo will not be rejected by the patient’s body, so they could be very useful in treating the patient.
the importance of meristems
these meristems allow plants to create new cells for growth
the stems cells can be used to produce clones of plants quickly
Advantages of stem cells for plants
- rare species can be cloned to protect them from extinction
- large numbers of identical crop plants with special features such as disease resistance, can be made
concerns about using stem cells
there may be risks, such as the transfer of viral infection
they may have ethical or religous obligations
why is cell division by mitosis important
growth and development of multicellular organisms
repairing damaged tissues
asexual reproduction
potential uses for stem cells
pancreatic islet cells
bone marrow
neurons
blood
heart muscle
what must a cell do before it can divide
before a cell can divide, it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria
