OCR A-level Biology- Cell division

what are the 3 stages of the cell cycle

Growth/G , synthesis/S and mitosis/M

what occurs in the G1 stage

organelle replication/cell increases in size/protein synthesis/respiration

what happens at the G1 checkpoint

the cell size is checked and the DNA is checked for damage

what occurs in the S stage

DNA replication

what occurs in the G2 stage

same as G1 but increasing cell size and cellular respiration is emphasised

what occurs at the G2 checkpoint

the DNA is checked for errors during replication

what are the stages of mitosis

prophase, metaphase, anaphase and telophase

what happens at the M checkpoint

the spindle fibres are checked to ensure that they have attached correctly

what happens if the cell fails any checkpoints

it enters G0 and leaves the cell cycle

what is a senscent cell

a cell that has reached the maximum number of divisions

what are proto-oncogenes

normal genes that code for proteins regulating cell growth and differentiation

what can proto-oncogenes mutate into

oncogenes

why do proto-oncogene mutations occur

because of carcinogens e.g. UV/X-Rays/smoking

what is the first stage of mitosis and what happens

during prophase 2 sister chromatids condense/nuclear envelope dissolves/spindle fibres form

what is the second stage of mitosis and what happens

during metaphase the chromatids line up along the metaphase plate

what is the third stage of mitosis and what happens

during anaphase the spindle fibres contract pulling the chromatids apart to opposite poles of the cell/centromeres divide

what is the fourth stage of mitosis and what happens

during telophase the nuclear envelope reforms/chromosomes decondense/nucleoli reform

what is the final stage of mitosis and what happens

during cytokinesis the cells separate/cytoplasm divides

what is produced in mitosis

2 diploid, identical daughter cells

what type of cells reproduce by mitosis

bodily cells

how does cytokinesis occur in animals

an actin ring forms at a cleavage furrow

how does cytokinesis occur in plants

2 vesicles fused with the cell surface membrane and then new sections of the cell wall develop at the cell plate

what occurs in stage 1 of meoisis 1 and what is it called

in prophase 1 bivalents form from two homologous chromosomes, crossing over occurs

what occurs in stage 2 of meiosis 1 and what’s it called

independent assortment of the homologous chromosomes at the metaphase plate

what occurs in stage 3 of meiosis 1 and what’s it called

in anaphase 1 the homologous chromosomes split at the centromere forming sister chromatids

what occurs during stage 4 of meiosis 1 and what’s it called

in telophase 1 the cells split apart ready for meiosis II

what occurs in meoisis II

meiosis II follows the same process as mitosis

what is a loci

the position of a gene on a chromosome

what are specialisations of a sperm cell

they have a haploid nucleus/have many mitochondria/have a flaggelum

what is an allele

different forms of the same gene

what are chromosomes that haven’t exchanged genetic material called

recombinant chromosomes

what are specialisation of erythrocytes

bioconcave shape/no nuclei/flexible

what are the specialisations of a neutrophil

they have a multi-lobed nucleus/granular cytoplasm (contains many lysozymes)

what are specialisations of squamous epithelium

contains squamous epithelial cells

what are specialisations of ciliated epithelium

they contain cilia/goblet cells

what is a tissue

contains multiple cells working together for a common purpose/goal/function

what are the specialisations of a palisade cell

contains chloroplast/shaped like rectangular boxes/large vacuole/chloroplast can move

what are some specialisations of guard cells

they can swell and shrink/the cell wall is thicker on one side

what are some specialisations of a root hair cell

have root hairs

what is a totipotent stem cell

a cell that can differentiate into any body cell or extra embryonic tissue

where are totipotent stem cell found

they are found for a limited period of time in zygotes

what is a pluripotent stem cell

a stem cell that can differentiate into any type of bodily cell

what is a multipotent stem cell

a stem cell capable of differentiating into any cell within a specific organ/tissue

what is a unipotent stem cell

a stem cell that can only differentiate into the same type of cell

what is an ips

induced pluipotent cells are cells removed from adult somatic cells and certain genes are activated allowing it to behave as a blastocyst