cell division, cell diversity and cell differentiation

Question 1

what are the main stages of mitosis

Answer 1

prophase
metaphase
anaphase
telophase

Question 2

how is the cell cycle regulated

Answer 2

g1/s checkpoint and g2/M checkpoints are the main ones. they prevent uncontrolled division which would lead to tumours and cancer
they repair damage to DNA for example from UV light

they also ensure the cycle cannot be reversed
and the DNA is only duplicated once during each cell cycle

Question 3

description of prophase

Answer 3

chromosomes replicated now shorten and thicken as the DNA supercoils nuclear envelope breaks down/ centriole in animal cells divides and move to opposite poles. cytoskeleton protein threads form spindle between these centrioles,

Question 4

descripton of metaphase

Answer 4

pairs of chromatids attach to the spindle threads at the equator region
they attach by their centromeres

Question 5

description of anaphase

Answer 5

the centromere of each pair of chromatids splits
motor proteins walking along the tubilin threads pull each sister chromatid of a pair in opposite directions, towards opposite poles
because their centromere goes first the chromatid, now called chromosome, assume a V shape

Question 6

description of telophase

Answer 6

the separated chromosomes reach the poles. a new nuclear envelope forms around each set of chromosomes.
the cell now contains 2 nuclei each genetically identical to each other

Question 7

stages of cell cycle

Answer 7

M phase-cell- a checkpoint which triggers condensation of chromatin, halfway through the cycle the metaphase checkpoint ensures that the cell is ready to complete mitosis.

g0 phase a resting phase cells may undergo apoptosis cell differentiation or senescence. some types of cells remain in this phase for a very long time or indefinitely

g1 phase- cells grow and increase in size, transcription of genes to make rna occurs. organellses duplicate biosynthesis,

s synthesis phase of interphase- once cell has entered this phase it is committed to completing the cell cycle. DNA replicates. when all chromosomes have been duplicated each one consists of a pair of identical sister chromatids.

g2- special chemicals ensure that the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of the spindle. cells grow

Question 8

what is the function of mitosis

Answer 8

growth, cell replacement and asexual reproduction.