Chapter 5: Mitotic Cell Cycle (SEE DIAGRAMS OF PHASES IN NOTES AS WELL) Flashcards
what is a chromosome
rod-shaped, deeply stained body that is visible in the nucleus at mitosis and meiosis,, each is made up of 2 sister chromatids
what are sister chromatids
- 2 sister chromatids make up 1 chromosome
- each sister chromatid consists of 1 very long DNA that wraps around histone proteins
what is a nucleosome
a repeating unit in eukaryotic chromatin, made up of DNA wrapped around 8 histone proteins,, they are linked by linker DNA
what is chromatin
- loosely coiled, thread-like nucleoprotein, found in the nucleus, which shortened, thickened and condensed into chromosomes during mitosis and meiosis
- during interphase, chromosomes exist as chromatins (euchromatin and heterochromatin)
what does cell division involve
cell division = mitosis(nuclear division) + cytokinesis (cyto division)
what are the functions/uses of cell divisions
- growth of multicellular organisms
- repair/replacement
- asexual reproduction
what does growth of multicellular organisms involve
- cell division to increase cell number
- cell enlargement to increase cell size
- these both involve cell differentiation
what does repair/replacement involve
- repair tissues by cell replacement
- replacement of damaged cells (skins/RBC)
- regenerate lost parts of the body in certain organisms
what does asexual reproduction involve
- binary fission (e.g. amoeba)
- budding (e.g. yeast)
- asexual spore (e.g. fungus)
- vegetative propagation
- fragmentation
what is cell maturation
a process whereby cells specialized in structure and functions (e.g. epidermal cells, xylem element and sieve tube element)
what are the zones of cell maturation
- zone of differentiation
- zone of elongation
- zone of cell division
what is growth
permanent increase in dry mass of living matter (cells and cellular content of living cells in the body exceept H2O)
what is living matter
cells and cellular content of living cells in the body (except H2O)
how does mitosis aid in repair and replacement
injured tissue is being repaired by:
- replacing the damaged and/or dead cells by cell division
- sometimes scar tissue is formed
examples of animals that can regenerate large body parts by cell division
- flatworm (any part)
- sea star (limbs and whole body if centre is intact)
- axolotl (limbs and spine)
- frog (tadpoles only can for limbs)
types of asexual reproduction involving mitosis
- binary fission
- budding
- asexual spore
- vegetative propagation
- fragmentation
what is binary fission
divides into 2
what is budding
- an outgrowth/bud is produced from parental body by cell divisions
- the bud may detach from parental body and become a seperate organism
what is asexual spore
from fungus
what is vegetative propagation
- new plants grows from vegetative (non flower) part of the plant by cell division
- grows from stem, root, leaf, bud or tuber
what is fragmentation
-when the body is cut into a few parts, each part can grow into a new organism by cell division
what is the role/function of mitosis for organisms
- growth
- repair, replacement and regeneration
- asexual reproduction
importance of mitosis
- to produce daughter cells that are genetically identical among themselves and with the parent cell (same number and type of chromosomes)
- maintain genetic stability of cells
what happens if cells do not undergo mitosis
- mutated
- rejected
- removed by immune system
what is the cell cycle
period from the formation of a cell to its division into 2 daughter cells
what are the 3 main stages of the cell cycle
- interphase (80%)
- mitosis(15%)
- cytokinesis (5%)
what is gap 1 phase
- growth phase of cell
- RNA and protein synthesis
- metabolic activities
what is gap 2 phase
- growth phase continues
- centrioles replication
- organelles replication
what is synthesis phase
- DNA replication
- histone protein synthesis
what is cytokinesis
cytoplasmic division (mitosis is nuclear division)
what are the 4 consecutive phases of mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
what happens in prophase
-chromatins shorten and thicken to become chromosomes
-in animals, centrosomes (centrioles surrounded by a large number of proteins)
move to opposite poles
-asters are formed
-nucleolus disappeared
-nuclear envelop disintegrates into small vesicles
-spindle fibres (made of microtubules) are formed from centrosome (the microtubule organising center MTOC)
What happens in metaphase
- chromosomes line up at equator of spindle fibres
- spindle fibres attach to kinetochore, the protein surrounding centomere
- each chromosome has 2 kinetochores at its centromere, one on each chromatid
what is the role of the centrosome
- attaches the 2 sister chromatids together
- for the spindle fibres to attach to
what is the role of the centrosome
- attaches the 2 sister chromatids together
- for the spindle fibres to attach to
what happens in anaphase
- shortest stage: difficult to see and least cells are seen at this stage
- centromeres divide into 2
- spindle fibres pull the sister chromatids apart to opposite poles
- by shortening of the microtubules from both ends (i.e. pole end and kinetochore end)
- sister chromatid becomes āVā shape
- centromeres leading towards the poles
what happens in telophase
- chromosomes arrive at the opposite poles
- chromosomes uncoil and elongate to become chromatids
- spindle fibres disintegrate
- nuclear envelope reforms at each pole
- nucleoli reappear
- 2 daughter nuclei which are genetically identical (same number and type of chromosomes) are formed
what happens in cytokinesis in animal cells
- by furrowing (narrowing of the cell surface membrane at the equator until it cuts the cell into 2)
- due to constriction of belt of microfilaments beneath the cell surface membrane
- organelles are evenly distributes to the 2 daughter cells
what happens in cytokinesis in plant cells
- cannot furrow due to rigid cell walls
- cell plate is formed at the equator from small fluid-filled vesicles from Golgi apparatus
- cellulose in vesicles form the new cellulose cell wall
- pectin in vesicles form the middle lamella
- membrane of the vesicles form the new cell surface membrane
what is a tumor
an irregular, solid mass of cells resulting from uncontrolled cell division
what are the 2 types of tumours
- benign tumor
- malignant tumor (cancer)
what are the 5 steps in cancer formation
- mutation
- uncontrolled cell division
- tumor division
- invasion of blood vessels and lymph vessels
- metasis
what is mutation
change in the base sequences of DNA/change chromosome number and structures in genes that control cell division
what mutation in genes control cell division
- proto-oncogenes
- tumor suppressor genes
- oncogenes
what are proto-oncogenes
before cancer is formed, this gene controls cell division and prevents cancer
what are tumor suppressor genes
-slows down cell division, repairs DNA , apoptosis (programmed cell death)
what are oncogenes
- divide indefinitely
- immortal (no apoptosis)
- lost contact inhibition
- does not differentiate (only divide)
what is a carcinogen
an ionising radiation (x-ray, UV), carcinogenic chemical (tar in tobacco, osbestos) or viral infection that leads to the formation of cancer cells
what are the causes of cancer
- carcinogen
- genetic heredity
- aging
stages of lung cancer formation
- cancer cells are not differentiated
- no cilia
- no mucus
- block bronchi
- invade blood vessels
what is a telomere
- a region of repetitive nucleotide (monomer of DNA) sequence at each end of a chromosome which protects the end of a chromosome from deterioration
- they contain a unique DNA of sequence (DNA + histone protein) which is repeated several times (base sequence)
what is the function of telomere
to protect the chromosomes from damage and ensure that when DNA is replicated, the ends of the molecules are included in the replication and not left out
what are stem cells
a relatively unspecialized cell that can divide an unlimited number of times by mitosis and has the potential to become a speicalised cell
- they are in embryo or adult
- each new cell has the potential to remain a stem cell or differentiate into one or several different cell types
what is potency
- the ability of a stem cell to produce different cell types
- it is variable
what are the 3 potencies
- totipotent
- pluripotent
- multipotent
what is totipotent
completely undifferentiated stem cell that can produce any type of cell (e.g. zygote forming placenta and embryo)
what is pluripotent
descendants of totipotent cells (mostly undifferentiated) and can differentiate into nearly all cells
what is multipotent
stem cell that can differentiate into a number of cell types, but only those of a closely related family of cells
what is stem cell therapy
introduction of new adult stem cell into damaged tissue to treat disease or injury
-e.g bone marrow transplantation to treat leukemia, growing of new tissues and organs
what is cell differentiation
a process whereby similar cells become dissimilar and specialized to take up different structure and function by switching on different genes at different place and time
what is asexual reproduction
the production of new individuals (offsprings) by one parent, whereby the offsprings are genetically identical among themselves and with the parent
relationship between SA:V and exchange of materials
-a cell cannot increase in size indefinetly as the SA:V limits its size for efficient exchange of material between external and internal environment of the cell
what are microfilaments role in cell division
microfilaments are involved in cytoplasmic movements, for example, during cytoplasmic streaming and cell movement, and the cytoplasmic constriction at cell division in animal cells
