Cell division by Mitosis + Stem Cells Flashcards
What is found in the nucleus
Chromosomes are found in the nucleus
What are chromosomes made up of
Chromosomes are made up of a molecule called DNA.
What do body cells contain
Body cells contain two of each chromosome. They are paired
How many pairs of chromosomes do Human body cells contain
Human body cells contain 23 pairs of chromosomes
What types of cells in have chromosomes that are not paired
Gametes have chromosomes which are not paired (human gametes have 23 single chromosomes)
How many chromosomes do human gametes have
human gametes have 23 single chromosomes
What do chromosomes carry
Chromosomes carry a large number of genes which determine many of our features
Rank from biggest to smallest
cell, chromosome, gene, dna, nucleus
Cell, nucleus, chromosomes, DNA, Gene
What is a chromosome
A chromosome is a long molecule of DNA found in the nucleus.
What is DNA
DNA is the molecule in cells that stores genetic information
What is a gene
A gene is a short section of DNA, found on a chromosome, which contains the instructions needed to make a protein
What is a gamete
A sex cell e.g. an egg cell or a sperm cell in animals
Describe the process of mitosis
In the first stage of the cell cycle, the DNA replicates to form two copies of each chromosome
The cell also grows and copies its sub-cellular structures such as mitochondria and ribosomes
In the second stage of the cell cycle, mitosis takes place.
One set of chromosomes is pulled to each end of the cell. The nucleus also divides
In the final stage of the cell cycle, the cytoplasm and the cell membrane divide to form identical cells.
Which stage of the cell cycle takes the longest
Replication of DNA to form copies of each chromosome and synthesis of new sub-cellular structures.
Functions of mitosis/Importance of mitosis
- Mitosis is essential for growth and development of multicellular organisms (e.g. plants and animals)
- Mitosis takes place when an organism repairs itself (e.g. when a broken bone heals)
- Mitosis happens during asexual reproduction
What is a stem cell
A stem cell is an undifferentiated cell which can give rise to more cells of the same type and can differentiate to form other types of cells
What is an embryonic stem cell
Embryonic stem cells are stem cells from an early embryo that can differentiate to form the specialised cells of the body
What are adult stem cells
Adult stem cells are stem cells that are found in adults that can differentiate and form a limited number of cells
Describe why differentiation is important in living organisms
All cells in an early animal or plant embryo are unspecialised (stem
cells).
Differentiation fulfils organisms’ requirements for different cells to carry
out different roles (e.g., muscle cells, sperm cells, gut lining cells).
Describe where stem cells are found in animals and plants
In animals
Embryonic stem cells are found on the inside layer of an embryo
Adult stem cells are found in bone marrow, skin, eyes, brain
Describe the process of differentiation
A sperm cells joins with an ovum (egg cell) to form a zygote, a single new cell. This is called fertilisation.
The fertilised ovum now undergoes mitosis and forms a ball of cells called an embryo. The inner cells of this ball are the embryonic stem cells that differentiate to form all of the specialised cells of your body.
Overtime these cells continue to undergo mitosis. They also change and begin to form specialised cells such as nerve cells and muscle cells.
This process is called differentiation
Order the steps of differentiation
Ovum + sperm cell
Embryo
Fertilised ovum
Nerve cells + muscle cells
Ovum + sperm cell
Fertilised ovum
Embryo
↓ differentiation
nerve cells + muscle cells
Adult stem cells are only found in _____
Adult stem cells are only found in certain places
Describe the function of stem cells in embryo’s
Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
Describe the function of stem cells in adult animals
Stem cells from adult bone marrow differentiate to form cells found in our blood such as: red blood cells, white blood cell and platelets
Adult stem cells ______ differentiate into any other ______of cell
Adult stem cells cannot differentiate into any other type of cell
State some ways that stem cells are useful in medicine
Bone marrow transplants
Therapeutic cloning
Explain how stem cells are used in bone marrow transplants
Leukaemia is a cancer of the bone marrow.
To treat this, the patient’s existing bone marrow is destroyed using radiation
The patient then receives a transplant of bone marrow from a donor
The stem cells in the bone marrow divide and form new bone marrow. They also differentiate and form blood cells.
Problems with bone marrow transplants
The donor has to be compatible with the patient. Otherwise the white blood cells produced by the donated bone marrow could attack the patient’s body.
There is a risk that viruses can be passed from the donor to the patient.
Explain how stem cells are used in therapeutic cloning
In therapeutic cloning, an embryo is produced with the same genes as the patient
This means that stem cells from the embryo can be transplanted into the patient without being rejected by the patient’s immune system.
Once inside the patient, the stem cells can then differentiate to replace cells which have stopped working correctly
This technique could be useful for a range of medical conditions such as diabetes or paralysis
Evaluate the use of embryonic stem cells and adult stem cells
The advantages of using embryonic stem cells is that many embryos can be created. It is a painless technique. Embryonic stem cells can also become any type of cell therefore treating many diseases
The disadvantages of using embryonic stem cells is that there is a possibility of harm or death to the embryo. The embryo cannot consent to the use of it’s cells. Also using embryonic stem cells is a unreliable technique that may not work
The advantages of using adult stem cells is that there are no ethical issues as patients can give permission. The adults stem cells can treat some diseases, the procedure is relatively sae and does not kill the donor. Patients recover quickly from the procedure and it is a reliable procedure.
The disadvantages of using adult stem cells is risk of infection from the procedure, it can only treat a few diseases and the procedure can be painful.
Both procedures advantage
Can treat the disease/problem
Both procedures disadvantages
risk of transfer of viral infection
Some stem cells can grow out of control and may become cancerous
In conclusion, even though the procedure when using adult stem cells is both ethical and reliable, the embryonic stem cell procedure is much more useful as it can treat many diseases.
What do roots and buds contain
Roots and buds contain meristem tissue
Describe the function of meristem cells in plants
Meristem tissue in plants can differentiate into any type of plant cell,
at any point in the life of the plant
State the advantages of using meristem cells
A rare plant could be cloned to stop it from going extinct.
Cloned crop plants could be produced for farmer
- Crop plants with special features such as disease resistance can be
cloned to produce large numbers of identical plants for farmers.
