mitosis Flashcards
asexual reproduction
production of genetically identical offspring from a single parent cell or organism growth both result of miotoic cell division
sexual reproduction
dependent on mitosis needs two parents genetically vary
what happens in mitosis
chromosomes of cell duplicated and genetic information equally shared out between two daughter cells that result
whats a chromosome
made up of a mass of coiled threads of dna and proteins
chromosomes of cell thats not actively dividing
chromosomes translucent to light and electrons so cant see them clearly
chromosomes of cells that are actively dividing
they condense become shorter and denser. they take up stain better and can see individual chromosomes
histones
positive charged basic protein
role of histones
help dna molecules condense to be packed closely and well
nucleosomes
when dna winds around histones to form dense cluster
what do nucleosomes do
interact to make more coiling and supercoiling to form dense chromosomes
feature of supercoiled part of chromosomes
genes not available to be copied to make proteins
karyotype
image showing all chromosomes in a cell
cell cycle
regulated process of stages in which cells divide into two genetically identical daughter cells
interphase
period of non division when cells increase in mass and size and carry out normal cellular activities and replicate dna ready for cell division
order of cell cycle
G1
S
G2
mitosis
cytokinesis
G1 first stage of interphase
time between end of previous mitosis and start of chromosome duplication
in active cells G1 very short but can be longer in other cells
S stage 2 of interphase
stage when chromosomes replicate and become double stranded chromatids ready for next cell division
G2 third stage of interphase
time when organelles and other materials needed for cell division are synthesised before cell can divide
M
mitosis when cells are actively dividing
C
cytokinesis final stage when cells can become new separate cells
how is cell cycle controlled
number of chemical signals made in response to different genes
cyclins
small proteins that are control chemicals that control the cell cycle
what do cyclins attach to
cyclin dependent kinase enzymes
role of cyclin dependent kinases
formed phosphorylates changes shape of proteins to bring them to different stage of cell cycle
phosphorylation of chromatin
results in chromosomes becoming denser and phosphorykation of some proteins in nuclear membrane which leads to breaks down of nuclear membrane during cell division
examples of permenant cells
nerve cells
light sensitive cells of retina
cardiac cells
ATP in interphase
production of ATP stepped up to provide more energy needed as cells divide
order of cell cycle steps
interphase
prophase
metaphase
anaphase
telophase
cytokinesis
steps in prophase
chromosomes coil up
take up stain and visible
each chromosome has two daughter chromatids and attached to each from centromere
nucleolus breaks down and centrioles begin to pull apart to form spindle
centromere
point at which daughter chromatids join
process of metaphase
-nuclear membrane broken
-centrioles moved to opposite sides of centre
-forms set of microtubules = spindle
-chromatids jost on metaphase plate of spindle
-line up along plate
-each centromere with microtubule
anaphase step
-centromeres split then chromatids separate
-chromatids from different pairs to opposite side of cell
-spindles move chromatids using ATP
structure of spindles
made up of overlapping microtubules that have contractile fibres
contraction of overlapping fibres causes movement of chromatids
telophase of cell
-spindle fibres break down
-nuclear envelopes form around two sets of chromosomes
-nucleoli and centrioles re formed
-chromosomes unravel
-less dense and harder to see
cytokinesis in animal cells
-ring of contractile fibres tighten around center of cell
-continue to contract until two cells separated
cytokinesis in plant cells
-cellulose cell wall building form inside cell outwards
-two identical daughter cells formed
enter interphase for next cycle
clones
genetically identical organisms
advantages of asexual reproduction
doesnt rely on finding mate
-large number of offspring rapidly
-
disadvantages of asexual reproduction
offspring genetically same- problem when living conditions change if virus comes
sporulation
production of asexual spores capable of growing into new individuals
where is sporulation most common in
fungi
mosses
ferns
features of asexual spores
can survive adverse conditions and can easily spread over large distances
regeneration
when organism replaces part of lost body part
fragmentation
when organisms reproduce themselves from fragments of their body
examples of asexual reproduction
fragmentation
sporulation
regeneration
budding
outgrowth from parent that produces smaller but identical individual produced purely by mitotic cell division
what happens to bud from budding
detached from parent organism and has own existence
vegetative reproduction
version of reproductive budding in flowering plants
process of vegetative propagation
plants forms structure that develops into fully differentiated new plant identical to parent plant
what happens to new plant in vegetative propagation
propagated into stem leaf or root of parent only by mitotic division
perennating organs
vegetative propogation involves perennating organs that contain food store for photosynthesis and remain dormant in soil to survive adverse conditions
how farmers increase plant numbers cheaply
removing new seeds from runners
cutting bulbs of plants
cutting up rhizomes
how farmers induce fragmentation artificially
take small piece of plant part of shoot often and plant it to grow and develop by mitosis into new plant
parthenogenesis
process by which unfertilised egg develops into new indivudual
3 parts of growth
cell division
assimilation
cell expansion
define growth
permenant increase in cell number or size or mass or all three
dry mass
mass of body of organism with all water removed from it
meristem
region of mitosis and growth in plant shoot or root
