M5: Cell division Flashcards
How do unicellular organisms go through cell division?
cell division occurs by asexual binary fusion, therefore one organism becomes two without the use of sex cells and/or gametes
How do multicellular organisms go through cell division?
cell division occurs via mitosis and meiosis
What is mitosis used for? and what does it do?
for somatic cells, leads to the formation of two new identical cells that contribute to the growth, repair, and genetic stability of the organism
What is meiosis’ function?
gives rise to gametes and transmits genetic information from one generation to the next via reproduction.
Why does DNA replicate exactly?
so that all cells making up the body contain the same genetic code so they can function in a controlled and coordinated ability, as well as maintaining genetic stability
What is the main role and importance of meiosis?
- formation of gametes for vechiles of inhertience as they carry genes
- ensures chromosomes are not doubled up
- introduces genetic diversity
What happens in meiosis I (not stages, just basic summary)
diploid cells divide into haploid cells, and the chromosome number is halved
What happens in Meiosis II (not stages, just basic summary)
two cells divide again, resulting in 4 haploid 4 daughter cells. Each daughter cell has half the original number of chromosomes that the parent cell had, resulting in the creation of gametes.
stages of mitosis?
interphase, prophase, metaphase, anaphase, telophase, cytokinesis
What is interphase?
- DNA replicates via DNA synthesis
- DNA spreads out and is called chromatin
What happens during prophase?
- chromatin shortens and thickens and coils into chromosomes
- Each chromosome contains two copies of DNA
- Nuclear membrane begins to break down
- spindle fibres extend across cells
What happens during metaphase?
- chromosomes line up across the cell centre
- Each chromosome consists of 2 identical sister chromatids
What happens during anaphase?
- proteins in the centromere are cleaved, separating the sister chromatids
- each chromatid becomes a chromosome
- spindle fibres pull chromosomes apart to opposite ends of the cell
- now called daughter chromosomes
what happens during Telophase?
- Daughter cell chromosomes gather at opposite ends of a cell
- spindle fibres break down and nucleolus reappears, with it surrounding around the two
- mitosis/meiosis I is complete with two identical chromosomes to itself and the parent cell
What happens during cytokinesis?
- division of cytoplasm
- daughter nuclei separate
- pinches off (animals) or cell plate divides (plants)
What are telomeres?
DNA proteins on the end of a chromosome that prevent them from sticking together
