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