cell divison by mitosis Flashcards
What are chromosomes made up of?
Chromosomes consist of DNA molecules combined with proteins, containing genes which provide the instructions for protein synthesis.
What is a gene?
A section of DNA which codes for a protein.
How many chromosomes are found in the nucleus of human body cells?
46
How many chromosomes are found in the nucleus of gametes?
23
How are chromosomes arranged in the nucleus of a body cell?
Arranged in pairs - 46 chromosomes form 23 pairs.
What are the three main stages of the cell cycle?
- Replication of DNA and synthesis of organelles
- Mitosis
- Division of cell
Why is mitosis important?
● Produces identical cells which all have the same genetic information.
● Produces additional cells for growth and repair.
Describe the first stage of the cell cycle
Longest stage
- cells grow and increase in mass
- replicate DNA
- synthesise more organelles (eg. mitochondria, ribosomes).
Describe the second stage of the cell cycle
Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.
Describe the third stage of the cell cycle
The cytoplasm and cell membrane divide - two identical daughter cells are produced.
What are the functions of mitosis?
1- essential for growth n development of multicellular organisms
2- when an organism repairs itself
3- asexual reproduction
What is a stem cell?
An unspecialised cell which is capable of differentiating into other cell types and of self-renewal.
What is the function of stem cells in embryos?
- Embryonic stem cells can replicate themselves and differentiate into many other types of cells.
- may be able to treat conditions such as paralysis and diabetes by dividing to replace damaged cells.
What is the function of stem cells in adult bone marrow?
- Adult stem cells can differentiate into several cell types to replace dead or damaged tissues.
- bone marrow stem cells can form many different types of blood cell.
What is the function of stem cells in plant meristems?
Meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifespan
- they can differentiate into any cell which is required by the plant.