Cell Division and Stem Cells Flashcards
What is a gene?
A section of DNA on a chromosome that codes for the production of a specific protein
How many chromosomes does a typical human body cell have?
46 chromosomes (23 pairs)
How does the 23rd pair of chromosomes differ in males and females?
- Females have two X chromosomes, ‘XX’
- Males have one X and one Y chromosome, ‘XY’
When do cells divide by mitosis?
- When an organism grows
- When an organism becomes damaged and needs to produce new cells
Give the 6 steps to the cell cycle.
- Cell growth
- DNA synthesis - chromosomes become double-stranded
- Further growth, and DNA checked for errors
- Mitosis (cell division)
- Cytoplasm separates - two cells are formed
- Resting period - cell stops dividing
Give the 5 steps to cell division by mitosis.
- The cell begins to divide.
- The DNA replicates to form 2 copies of each chromosome.
- The nuclear membrane breaks down, and the chromosomes line up in the centre of the cell.
- One set of chromosomes is pulled to each end of the cell, and the nucleus divides.
- The cytoplasm and cell membrane divide to form two identical cells.
How many daughter cells are produced in mitosis?
Two
What is a stem cell?
An unspecialised cell which has not yet undergone differentiation (and can differentiate into many cell types)
Where can adult stem cells be found in the body?
- brain
- eyes
- blood
- heart
- liver
- bone marrow
- skin
- muscle
What do stem cells in the bone marrow differentiate into?
Blood cells
Where does cell division occur in plants?
In meristems, a region in plant roots and shoots
When can plant cells in the meristems differentiate?
At any point during the life of the plant
What is the name given to a fertilised egg cell?
Zygote
Cells from plant meristems can be cloned.
Give the four steps to clone a cell from a plant meristem.
- Tissue sample is scraped from a parent plant.
- Tissue sample is placed in a Agar growth medium, which contains nutrients and plant hormones to stimulate growth.
- Sample develops into tiny plantlets.
- Plantlets are planted into compost to allow further growth.
What is an advantage and disadvantage of using embryonic stem cells?
ADVANTAGE - Can differentiate into a wider range of cell types
DISADVANTAGE - Difficult to obtain, and their use raises ethical challenges
What are advantages of using adult stem cell transplants?
Use the patient’s own stem cells. so will not be rejected by the patient’s immune system.
What is therapeutic cloning used for?
To produce stem cells with the same genetic make-up as the patient
Describe the steps to therapeutic cloning.
- Nucleus is removed from the egg of a human donor.
- Nucleus is removed from patient’s cell and transferred into donor’s egg cell.
- Cell is stimulated to divide, and develops into an embryo.
- After 4-5 days, stem cells are removed for therapeutic use.
Which kind of cell division is used in the production of gametes (sex cells)?
Meiosis
Human gametes are haploid. What does haploid mean
Half the number of chromosomes than a normal body cell has (23 single chromosomes)
Human gametes are haploid. What does haploid mean?
Their nucleus only contains a single set of 23 unpaired chromosomes
How many daughter cells are produced in meiosis?
Four
In mitosis, are daughters cells genetically identical or genetically different to their parent cells?
Genetically identical
In meiosis, are daughters cells genetically identical or genetically different to their parent cells?
Genetically different
Give the 5 steps to meiosis.
- Chromosomes make identical copies of themselves.
- Similar chromosomes pair up.
- Sections of DNA get swapped between chromosomes.
- Pairs of chromosomes divide.
- Chromosomes divide again.
