Cell cycle
Cell cycle – process in multicellular organisms where body cells divide to produce new cells
Cell cycle starts when cell has been produced by cell division and ending with the cell dividing to
form 2 new identical cells
Interphase – stage of cell growth and DNA replication
Mitosis – cell reproduced itself by dividing into 2 to produce 2 genetically identical daughter cells
Cytokinesis – division of the cytoplasm
Interphase – cell growth and increase number of subcellular structures in cell like mitochondria and
ribosomes
DNA is duplicated to form X shaped chromosome, with each arm of the X chromosome/ chromatid
an exact replica of the other
Prophase – chromosomes condense, becoming shorter and fatter, nuclear membrane breaks down
and chromosomes lie free in the cytoplasm
Metaphase – chromosomes line up in the centre of the cell
Anaphase – spindles fibres pull the chromosomes apart, chromatids pulled to opposite poles of the
cell
Telophase - Membranes form around each new set of chromosomes and these become the nuclei of
the two new cells, the nucleus has divided
Cytokinesis – cytoplasm and cell membrane divide to form 2 new cells
Interphase – cell prepares for division, chromosomes replicate themselves to because 2 chromatids
held together at the centromeres
Prophase- chromosomes shorten and thicken and individual chromosomes are now visible,
centrioles move to opposite poles of the cell and the nuclear membrane begins to break down
Metaphase – chromosomes line up along the equator, spindle fibres form and attach to the
chromatids
Anaphase – spindle fibres shorten pulling the chromatids apart, they are now chromosomes
Telophase – chromosomes unravel again, the cell divides into 2 and the nuclear membrane reforms,
2 genetically identical daughter cells have been formed
Mitosis
Mitosis is used for:
By multicellular organisms to grow
By multicellular organisms to repair and replace damaged cells
By some organisms for asexual reproduction
e.g. strawberry plants form runners by mitosis that take root so new plants can grow from them also
by mitosis, the offspring are clones of the parent plant
mitosis formula – 2^n
, comparison:
Mitosis Meiosis
46 chromosomes 23 chromosomes
2 cells formed 4 cells formed
Growth, repair asexual Sexual
2n n
6 stages 10 stages
Nucleus of cell Testes and ovaries
Somatic - any body cell not gamete
Zygote – mitosis
Embryo – begin differentiation
growth and development
growth – increase in size or mass
cell division by mitosis leads to growth
cell differentiation – cell changes to become specialised to perform one specific function
specialised cells allows organisms to function more efficiently because they carry out different
functions
plants also grow by cell elongation – plant cell expands so the cell becomes larger and the plant
grows
in animals growth is mainly by cell division
because animals tend to grow when they are young, mitosis happens at a faster rate when you are
old mitosis is largely for repair so it is slower
also cell differentiation is lost at an earlier age
in plants growth is mainly due to cell elongation
cell division only happens in the roots and shoots (meristems), but because plants grow continuously
plants will continue to differentiate to form new leaves and roots
circulatory – transport substances, defend body, control temperature
excretory – remove watse product and unwanted substances, regulate water content
muscular – movement
nervous – respond to internal and external stimuli and conditions, carry messages so body works
as co-ordinated whole
respiratory – deliver O2 for respiration and remove waste
reproductive – bring about fertilisation to produce new offspring
skeletal – bring about movement, support and protect internal structures, produce blood cells,
store and release Ca
body controls the amount of cell division that happens for growth, so cells normally stop dividing
when enough new cells have been produced
Cell cycle – process in multicellular organisms where body cells divide to produce new cells
Cell cycle starts when cell has been produced by cell division and ending with the cell dividing to
form 2 new identical cells
Interphase – stage of cell growth and DNA replication
Mitosis – cell reproduced itself by dividing into 2 to produce 2 genetically identical daughter cells
Cytokinesis – division of the cytoplasm
Interphase – cell growth and increase number of subcellular structures in cell like mitochondria and
ribosomes
DNA is duplicated to form X shaped chromosome, with each arm of the X chromosome/ chromatid
an exact replica of the other
Prophase – chromosomes condense, becoming shorter and fatter, nuclear membrane breaks down
and chromosomes lie free in the cytoplasm
Metaphase – chromosomes line up in the centre of the cell
Anaphase – spindles fibres pull the chromosomes apart, chromatids pulled to opposite poles of the
cell
Telophase - Membranes form around each new set of chromosomes and these become the nuclei of
the two new cells, the nucleus has divided
Cytokinesis – cytoplasm and cell membrane divide to form 2 new cells
Interphase – cell prepares for division, chromosomes replicate themselves to because 2 chromatids
held together at the centromeres
Prophase- chromosomes shorten and thicken and individual chromosomes are now visible,
centrioles move to opposite poles of the cell and the nuclear membrane begins to break down
Metaphase – chromosomes line up along the equator, spindle fibres form and attach to the
chromatids
Anaphase – spindle fibres shorten pulling the chromatids apart, they are now chromosomes
Telophase – chromosomes unravel again, the cell divides into 2 and the nuclear membrane reforms,
2 genetically identical daughter cells have been formed
Mitosis
Mitosis is used for:
By multicellular organisms to grow
By multicellular organisms to repair and replace damaged cells
By some organisms for asexual reproduction
e.g. strawberry plants form runners by mitosis that take root so new plants can grow from them also
by mitosis, the offspring are clones of the parent plant
mitosis formula – 2^n
, comparison:
Mitosis Meiosis
46 chromosomes 23 chromosomes
2 cells formed 4 cells formed
Growth, repair asexual Sexual
2n n
6 stages 10 stages
Nucleus of cell Testes and ovaries
Somatic - any body cell not gamete
Zygote – mitosis
Embryo – begin differentiation
growth and development
growth – increase in size or mass
cell division by mitosis leads to growth
cell differentiation – cell changes to become specialised to perform one specific function
specialised cells allows organisms to function more efficiently because they carry out different
functions
plants also grow by cell elongation – plant cell expands so the cell becomes larger and the plant
grows
in animals growth is mainly by cell division
because animals tend to grow when they are young, mitosis happens at a faster rate when you are
old mitosis is largely for repair so it is slower
also cell differentiation is lost at an earlier age
in plants growth is mainly due to cell elongation
cell division only happens in the roots and shoots (meristems), but because plants grow continuously
plants will continue to differentiate to form new leaves and roots
circulatory – transport substances, defend body, control temperature
excretory – remove watse product and unwanted substances, regulate water content
muscular – movement
nervous – respond to internal and external stimuli and conditions, carry messages so body works
as co-ordinated whole
respiratory – deliver O2 for respiration and remove waste
reproductive – bring about fertilisation to produce new offspring
skeletal – bring about movement, support and protect internal structures, produce blood cells,
store and release Ca
body controls the amount of cell division that happens for growth, so cells normally stop dividing
when enough new cells have been produced
