B2 Cell division Flashcards
What happens before a cell divides?
It makes a copy of every chromosome’s DNA
What happens to the nuclear membrane?
It breaks down
What happens to the chromosomes during mitosis?
- They join up in the centre of the cell
- They then separate to opposite sides of the cell
- New nuclear membranes form and the cell begins to divide
What is special about the two cells produced during mitosis?
They are genetically identical
What is a gene?
A short section of DNA that codes for a protein/controls a characteristic
What are chromosomes?
Thread-like structures in the nucleus that carry genes
What is DNA?
Deoxyribonucleic acid, the material of inheritance
What is mitosis?
Cell division that produces two genetically identical daughter cells
How many pairs of chromosomes are there in most human cells?
23
Why is mitosis important?
- Needed to produce cells that are needed for organisms to grow
- Needed to replace cells that have become worn out and repair damaged tissue
- Asexual reproduction
How many chromosomes are in one human body cell?
46
What is a stem cell?
Undifferentiated cell with the potential to become specialised
What are adult stem cells?
Stem cells that can only differentiate into a specific type of cell
Describe stage one of the cell cycle
Replication of DNA to form two copies of each chromosome and synthesis of new sub-cellular structures
Describe stage two of the cell cycle
Mitosis: one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides
Describe stage three of the cell cycle
The cytoplasm and the cell membranes also divide to form two genetically identical daughter cells
Where does differentiation occur in plants?
Meristems found in the shoot and root tips
Define cloning
Production of identical offspring by asexual reproduction/mitosis
How does cell differentiation varies in animals and plants?
- Many types of plant cells retain the ability to differentiate throughout life
- Most types of animal cell differentiate at an early stage of development
What are embryonic stem cells?
Stem cells from an early embryo that can differentiate into all cell types
Diseases that may be treated with stem cell treatment
- Paralysis
- Diabetes
- Blindness
How can we use stem cells to treat someone with type 1 diabetes?
Induce embryonic stem cells to produce healthy pancreas cells to make enough insulin
Why is the ability to clone plants quickly a benefit?
Produce large numbers of rare plants reliably and safely to stop their extinction and for research, agriculture advances
Problems with embryonic stem cells
- Some people feel that, as the embryo cannot giver permission, using it is a violation of its human rights
- Progress in developing therapies using embryonic stem cells has been relatively slow, difficult, expensive, and hard to control
- It is proving difficult to persuade embryonic stem cells to differentiate into the type of cells needed to treat patients
- Embryonic stem cells divide and grow rapidly, so they might cause cancer if they are used to treat people
Problems with adult stem cells
- There is a risk that adult stem cells might be infected with viruses, and so could transfer the infections to patients
- If stem cells from an adult are used to treat another unrelated person, they may trigger an immune response. The patient may need to take immunosuppressant drugs to stop their body rejecting their new cells
- adult stem cells can only differentiate into specific types of cells so there are a limited number of diseases that they can be used to treat
Therapeutic cloning
A cloned early embryo is produced, using cells from an adult, with the same genes as the patient so the stem cells produced are not rejected and may be used for medical treatment
Zygote
The single new cell formed right after fusion of gametes
Where do you get adult stem cells in animals?
Bone marrow
What is binary fission?
A type of cell division process by which prokaryotic organisms, like bacteria, divide and reproduce
what is differentiation?
the process where cells become specialised for a particular function
why is differentiation important in living organisms?
- all cells in an early animal or plant embryo are unspecialised
- differentiation fulfils organisms’ requirements for different cells to carry out different roles e.g. muscle cells, blood cells etc
explain how a transplant of bone marrow cells can help to treat medical conditions
- bone marrow cells are unspecialised and can differentiate into many different types of cells
- so will cure diseases where new cells are needed
what is one section of genetic material on a chromosome called?
gene
what are the similarities between prokaryotic and eukaryotic cells?
- both have a cytoplasm
- both contain DNA
- both have a cell membrane
- both have ribosomes
what are the differences between prokaryotic and eukaryotic cells?
- eukaryotic cells have a nucleus, prokaryotic cells do not
- prokaryotic cells are smaller than eukaryotic cells
- eukaryotic cells contain mitochondria, prokaryotic cells do not
- prokaryotic cells have plasmids, eukaryotic cells do not
name the cell division that produces genetically identical body cells for growth and repair
mitosis
describe three differences between the processes of mitosis and meiosis
- cells divide once during mitosis, but twice during meiosis
- meiosis produces four cells but mitosis produces two cells
- mitosis produces cells with two of each chromosome, meiosis produces cells with one of each chromosome
describe one similarity between the processes of mitosis and meiosis
- increase in the number of sub-cellular structures
- DNA replicates
why is mitosis important in living organisms?
to repair tissues
