B2.1 Supplying the Cell - Cell cycle & Mitosis Flashcards
Mitosis, differentiation, stem cells.
Define Mitosis
A type of nuclear cell division that is used by cells for growth, repair, and healing and asexual reproduction. A stage within the cell cycle.
What is the cell cycle?
- The process of cell growth and division for growth and repair of body cells
- It has three main stages interphase, mitosis and cytokinesis,
- Results in two identical daughter cells.
Why is interphase important?
- It it the stage of growth (G1) and replication (S)
- Before a cell can divide it needs to grow and duplicate all of its cellular contents
What are homologous chromosomes?
- A pair of chromosomes, one from the mother, and one from the father, which are very similar to one another and have the same size and shape.
- Most importantly, they carry the same type of genetic information: that is, they have the same genes in the same locations
What do the terms ‘diploid’ and ‘haploid’ mean?
- Diploid = full set of chromosomes, 23 pairs/46 strands in humans
- Haploid = half of the full set of chromosomes, 23 strands in humans
What is the name given to the two identical copies of each chromosome?
Sister chromatids
What is the name of the attatchment between sister chromatids?
Centromere.
What is the name given to the way in which DNA replicates?
Semi-conservative
What is meant by semi-conservative replication?
After replication each strand has one original strand, and one new ‘complementary’ strand
List the key stages in DNA replication.
- Double helix untwists
- Hydrogen bonds between bases broken, DNA ‘unzips’
- Bases exposed on each of the two strands
- Free nucleotides form hydrogen bonds with the exposed base (A-T, C-G)
- Covalent bonds form between nucleotides to form ‘backbone’
What happens during the cell cycle after DNA replication but before mitosis?
The replicated DNA is checked for errors and corrections made to avoid mutations being pass on to new cells
Explain what happens in each of the key stages of mitosis
- Prophase - Chromosomes align in the middle of the cell
- Metaphase - Spindle fibres pull the arms of each chromosome to opposite ends of the cell.
- Anaphase - Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells – the nucleus has divided.
- Telophase - Cytoplasm and cell membrane divide to produce two identical daughter cells, each containing the same chromosomes.
What is cytokinesis?
The formation of the two new nuclear membrane, and pinching in of the cell membrane to separate and enclose the two new nuclei, to separate the two new cells.
Explain why the chromosome number must stay the same when cells divide by mitosis?
The chromosome number must stay the same when cells divide by mitosis to ensure the cells produced are normal body cells, identical to their parent cell.
When do the sister chromatids condense>
During prophase the sister chromatids condense to form x-shaped chromosomes linked by a centromere.