2.1.6: cell division Flashcards
what is the cell cycle?
a highly ordered sequence of events, resulting in the division of cells and the formation of 2 genetically identical daughter cells
what happens during the mitotic phase and the interphase?
- mitotic = mitosis
- interphase = g1, synthesis and g2
what happens at the growth one phase of the cell cycle?
proteins from which the organelles are synthesised are produced and organelles replicate. the cell increases in size
what happens during the synthesis phase of the cell cycle?
dna is replicated in the nucleus
what happens during the growth two phase of the cell cycle?
the cell continues to increase in size, energy stores are increased and the duplicated dna is checked for errors
what is the g0 phase?
given to the phase when the cell leaves the cycle either temporarily or permanently, due to damages cells and many sensecent cells that could cause damage/harm to the body
where is the g1 checkpoint and what does it check for?
- at the end of the g1 phase before entering synthesis
- cell size, nutrients, growth factors and dna damage
where is the g2 checkpoint and what does it check for?
- at the end of the growth two phase before the start of the mitotic phase
- checks for any errors in the dna and if it is the correct size
where is the metaphase checkpoint and what does it check?
- point in mitosis where all the chromosomes should be attached to the spindle and have aligned
- that the chromosomes are assembled correctly
what are the 4 stages of mitosis?
prophase, metaphase, anaphase and telophase
what happens during mitosis?
1) prophase - chromosomes condense and become visible in the nucleus. nucleolus disappears and the nuclear membrane begins to break down. a pair of centrioles move to either side of the cell. spindle fibres move chromosomes toward the centre of the cell
2) metaphase - spindle apparatus are completely formed and chromosomes are lined up in the centre
3) anaphase - centromeres divide into two and spindle fires begin to shorten. this pulls the sister chromatids towards the opposite poles
4) telophase - nuclear membrane reforms. chromosomes uncoil back to their chromatin state and the nucleolus reappears in each nucleus
what are homologous chromosomes?
chromosome pairs that are the same length, have the same centromere position and have the same genes
what are the 8 stages of meiosis?
prophase one, metaphase one, anaphase one, telophase one, prophase two, metaphase two, anaphase two, telophase two and cytokinesis
what happens during meiosis?
1) prophase 1 - chromosomes condense and thicken to become visible. homologous chromosomes pair up and crossing can occur (swapping genetic information)
2) metaphase 1 - homologous chromosomes line up on the equator of the spindle fibres (independent assortment of homologous chromosomes - pairs are randomly lined up at the equator)
3) anaphase 1 - spindle fibres contract and chromosome pairs are separated
4) telophase 1 - chromosomes arrive at the opposite poles of the cell to form 2 daughter cells
5) prophase 2 - chromosomes in each daughter cell prepare to migrate to spindle fibres
6) metaphase 2 - the chromosomes at each pole of the cell line up along the spindle fibres (chromatids are randomly moving)
7) anaphase 2 - spindle fibres contract and sister chromatids are pulled towards the opposite poles
8) telophase 2 - chromatids arrive at opposite poles to form 4 daughter cells
why does mitosis occur?
the development of embryos and replacing damaged cells
what is meant by a differentiated cell?
it is specialised to carry out a very specific function
what is an erythocyte and how is it specialised?
> red blood cells that transport oxygen around the body
- biconcave shape gives a higher surface area to volume ratio
- there is no nucleus so there is more space
- it is flexible so it can fit through capillaries
what is a neutrophilis and how is it adapted?
> type of white blood cell in the immune systems
- multi-lobed nucleus which allows it to squeeze through small gaps
- many lysosomes that contain enzymes to attack pathogens
what are sperm cells and how is it adapted?
> male gametes that deliver genetic information to the female gamete
- has a tail for movement
- a lot of mitochondria for energy to swim
- digestive enzymes are released to digest the layers of the ovum
what is a palisade cell and how is it adapted?
> where photosynthesis takes place
- has a lot of chloroplasts to absorb a lot of light
- it is rectangular so it is closely packed
- has large vacuoles to maintain turgor pressure
- chloroplasts move to make sure more light is absorbed
what is a root hair cell and how is it adapted?
> on the surfaces of roots to take up water and - minerals from the soil to the plant
have long extensions to increase the surface area
- increases the amount of water and minerals absorbed
what is a guard cell and how is it adapted?
> control the size of the stomata to prevent water loss and intake carbon dioxide
- the cell walls are thicker on one side so it doesn’t change shape symmetrically as its volume changes
what is squamous epithelium tissue and how is it adapted?
> allows diffusion of oxygen into the blood from the lungs
- one cell thick, meaning faster and easier diffusion
what is the ciliated epithelium tissue and how is it adapted?
> lines the trachea to prevent particles and pathogens into the respiratory
- hair-like structures means they move in a rhythmic pattern
