Cell Division Flashcards
What does the nucleus of a cell contain?
Chromosomes made of DNA molecules
How many chromosomes does a human body cell contain?
46
23 pairs
What are gametes?
Sex cells. Male gametes are sperm and female gametes are eggs.
In what way are gametes different from body cells?
They only have a single set of chromosomes in their nucleus - half the genetic complement
Define haploid
A cell that has a nucleus with only one set of chromosomes; a sex cell
Define diploid
A cell that has a nucleus with two sets of chromosomes; body cells
What is a zygote?
Usually a diploid cell resulting from the fusion of a sperm and an egg (two haploid cells)
When do cells divide by mitosis?
When:
- An organism grows
- Organisms need to replace worn-out cells
- Organisms need to repair damaged tissue
What is the end produce of mitosis?
Two genetically identical daughter cells (diploid)
Describe the process of mitosis
- Chromosomes copy themselves, two strands are joined together
- The nucleus disintegrates. A spindle forms. Chromosomes line up on the spindle
- Spindle fibres contract and pull the two chromosome strands apart
- Nuclear membrane reforms in the 2 new cells
What is the fusion of gametes in meiosis called?
Fertilisation
What are gametes in flowering plants?
Pollen and eggs
What happens in meiosis?
- Copies of the genetic information are made
- The cell divides twice to form four gametes
- All gametes are genetically different - they show VARIATION
What does meiosis produce?
Gametes
What is the nuclear membrane?
The membrane that surrounds genetic material
What regulates the speed of the cycle of cell division?
Proteins withing the cell
What is cancer?
A group of diseases where changes in cells lead to uncontrolled growth and division of cells
What are the two types of tumour?
Malignant
Benign
What are malignant tumours?
Tumours that can invade neighbouring tissues and spread throughout the body in the blood, leading to the creation of more secondary tumours
What are benign tumours?
Tumours that stay in a specific part of the body, often within a membrane.
How do other tumours form from a malignant tumour?
A cell breaks off and invades other tissues
What problem can tumours cause?
Cutting off blood supply to healthy tissues
How do malignant tumours spread throughout the body?
Through the blood
What factors can increase likelihood of developing a cancerous tumour?
- Unhealthy diet
- Smoking
- Excessive alcohol intake
- Too much UV exposure
How can doctors treat cancerous tumours?
- Surgery to remove tissue
- Radiotherapy
- Chemotherapy
What are unspecialised cells called?
Stem cells/undifferentiated cells
How does differentiation happen?
Organisms start as one cell, then divide to form embryos that differentiate (specialise) to perform a bodily function
Where can plant stem cells be found?
In meristem tissue
When can a plant differentiate?
Its entire life
Where can adult stem cells be found?
*** Bone marrow *** Brain Eyes Blood Heart Liver Skin Muscle
Why are adult stem cells less useful than embryonic stem cells?
They can only differentiate into related cell types
e.g. bone marrow cells can only differentiate into blood cells and cells of the immune system
What can stem cells be used for medically?
To be transplanted into patients to treat medical conditions and disease where cells have been destroyed and need replacing
What can stem cells be used to treat?
- Type 1 diabetes
- Multiple sclerosis
- Spinal cord or brain injury
When are bone marrow transplants carried out?
- In cases of blood cell cancer e.g. leukaemia and lymphoma
- When blood cells have been destroyed e.g. during cancer treatment
What are the benefits of using one’s own stem cells in a transplant?
- No rejection
- No need to fin a donor
- No need for tissue matching
What can plant stem cells be used for?
- To quickly and cheaply clone plants
- Protect rare species of plant from extinction
- Create large populations of plants with special features e.g. disease resistance
What are the clinical issues around stem cell treatments?
- No guarantee of how successful the procedure will be
- Difficulty finding suitable stem cell donors
- Difficulty obtaining and storing a patient’s embryonic stem cells
- Mutated stem cells behave like cancer cells
- Cultured stem cells could be contaminated with a virus
What are the ethical issues around stem cell treatment?
- Source of embryonic stem cells is in vitro fertilisation
- It is right to create embryos for therapy and destroy them in the process?
- At what stage of development should an embryo be regarded as, and treated as, a person?
What are the social issues around stem cell treatment?
- Educating the public about what stem cells can and cannot do
- Whether the benefits can outweigh the risks
- Patients could be exploited by paying for expensive treatments and being given false hope of a cure as stem cell therapies are only in their developmental stages
Where are plant meristems found?
At root and shoot tips
