Cell division Flashcards
What are the two main forms of cell division and what are they?
Mitosis - A cell diving to for two genetically identical diploid daughter cells
Meiosis - A cell dividing (twice) to form 4 genetically different haploid daughter cells
What happens in a cell’s interphase?
Cell spends most of it’s life in interphase.
Split into:
Growth Phase 1 - Proteins and mRNA are synthesised
Synthesis - DNA replicates
Growth phase 2 - Energy is stored and organelles divide for cell division
What are the stages of mitosis and what happens in them?
Prophase - Chromosomes condense and become visible, and the nuclear membrane disintegrates
Metaphase - Chromosomes line up along the cell’s equator
Anaphase - The chromatids are pulled to opposite poles by spindle fibres
Telophase - The nuclear envelope reforms around the chromatids
Cytokinesis - The cytoplasm divides
Where are the checkpoints and what do they do?
After G1, G2 and metaphase. They ensure that cells with damaged or incorrectly separated chromatids do not continue to divide.
What are the steps of meiosis?
P1 M1 A1 T1 Small interphase P2 M2 A2 T2
What does the first stage of meiosis involve?
The homologous pairs of chromosomes splitting
What is a homologous pair?
A pair of chromosomes with the same genes but different alleles that are similar in length, gene position and centromere location.
What does the second stage of meiosis involve?
The division of sister chromatids
What factors of meiosis cause genetic variation?
- Crossing over - During Prophase 1, the homologous pairs of chromosomes cross over with each other and exchange segments. This means that the genes from the parents intermix.
- Reduction to haploid - It is equally likely for a given chromosome to be distributed to either of the two daughter cells.
- Random chromatid assortment - Sister chromatids separate randomly into daughter cells.
How are genetic diseases caused?
Errors in segregation during meiosis
