Topic 2a - Cell Division and Stem Cells Flashcards
What do you call body cells that have two copies of each cell?
Diploid cells
What is a chromosome?
Long lengths of a molecule called DNA. The DNA is coiled up to form the arms of the chromosome.
What is the cell cycle?
The cell cycle starts when a cell has been produced by cell division and ends with the cell dividing to produce two identical diploid cells.
What is the stage of the cell cycle where the cell divides, called?
Mitosis
What is mitosis?
Mitosis is when a cell reproduces itself by splitting in two to form two genetically identical offspring.
It usually refers to the division of the nucleus rather than the whole cell.
What happens during interphase, during the cell cycle?
1) In a cell that’s not dividing, the DNA is all spread out in long strings
2) Before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
3) It then duplicates its DNA- so there’s one copy of each chromosome for each new cell. The DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other. Each ‘arm’ is called a chromatid.
What happens during mitosis, during the cell cycle?
1) Prophase: the chromosomes condense, getting shorter and fatter. The membrane
around the nucleus breaks down and the chromosomes lie free in the cytoplasm.
2) Metaphase: the chromosomes line up at the centre of the cell.
3) Anaphase: spindle fibres pull the chromosomes apart. The two arms of each chromosome (chromatids) are pulled to opposite ends of the cell.
4) Telophase: membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells — the nucleus has been divided.
Before telophase ends, the cytoplasm and cell membrane divide to form two separate cells — this process is called cytokinesis.
What happens after mitosis, in the cell cycle?
At the end of mitosis, the cell has produced two new daughter cells. Each daughter cell contains exactly the same set of chromosomes in its nucleus - the two cells are genetically identical. They’re also genetically identical to the diploid parent cell. This makes the daughter cells diploid too.
What are the uses of mitosis?
- By multicellular organisms to grow
- By multicellular organisms to replace cells that have been damaged
- By some organisms to reproduce by asexual reproduction
How do you calculate the number of cells there are after multiple division of cell by mitosis?
2^n (n = the number of divisions by mitosis)
To what processes do animal cells grow and develop?
- Cell division: happens by mitosis
- Cell differentiation: the process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently because different cell types can carry out different functions.
To what processes do plant cells grow and develop?
- Cell division: happens by mitosis
- Cell differentiation: the process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently because different cell types can carry out different functions.
- Cell elongation: the plant cell expands, making the cell bigger, so making the plant grow
When do animal cells grow?
Animal cells tend to grow at a faster rate when they’re younger, than when they’re older
When do plant cells grow?
Cell division usually happens at the tips of roots and shoots (in areas called meristems). Plants grow continuously, at all ages.
What is the rate at which the cells divide by mitosis controlled by?
chemical genes in an organism’s DNA