1.6 cell cycle and cell division Flashcards
state the function of mitosis
to create 2 daughter cells with genetically identical nuclei as the parent cell
processes which involve mitosis
growth and repair
asexual reproduction
embryonic development
replacement of cells that die naturally
state the 4 phases of mitosis
Prophase, Metaphase, Anaphase, Telophase
what happens during prophase?
nuclear membrane breaks down making the nucleolus disappear. chromosome condense making them thicker and shorter. sister chromatids are then visible. centrioles move to opposite poles and spindle fibre forms for microtubules. nuclear envelope disintegrates
what happens during metaphase?
spindle fibre is fulled forms and replicated chromosomes align at the cells equator. spindle fibres attached themselves to centromere of the chromosomes as they align
what happens during anaphase?
a rapid stage where the centromere divided and the spindle fibre shortens which pull the sister chromatids to opposite pole of the cell
what happens during telophase?
chromatids have reached the opposite poles and have became distant. chromosomes uncoil and lengthen. spindle fibres breaks down, nuclear envelope reforms and nucleolus appears.
why must chromosomes condense during mitosis?
to ‘condense’ means to make the DNA denser or more tightly packed. DNA condenses during mitosis so it can easily be moved to the poles without getting tangled and/or broken
state the function of meiosis
produces cells which are haploid for sexual reproduction ( gametes )
how many cell divisions in meiosis
- the first is different from the phases in mitosis but 2nd is exactly the same
how many cell divisions in meiosis?
- first is different to the phases in mitosis however 2nd is completely the same
what happens during prophase 1?
chromatids condense and chromosomes form bivalents which are homologous pairs. chromatids may cross over forming chiasmata then the nuclear membrane disintegrates
what happens during metaphase 1?
homologous chromosomes align themselves in pairs along the equator. here independent assortment occurs when the homologous chromosomes from parent 1 and 2 align randomly along the spindle facing each pole.
what happens during anaphase 1?
the chromosome bivalents separate as each chromosome is pulled by its centromere (doesn’t split ) towards opposite poles
what happens during telophase 1?
chromosomes reach opposite poles of the cell which are now haploid due to chromosome pairs being separated; nuclear envelope reforms around the chromosomes
