Topic 11: Mitosis Flashcards
what is mitosis
the cell division of somatic cells
the chromosome number stays the same as one round of replication and one round of division
from one cell to two identical daughter cells with same chromosome content as parental cell (diploid 2n)
what is M phase made up of
nuclear division (mitosis) cellular division (cytokinesis)
how many rounds of mitosis are there during early development
50
why is mitotic growth necessary
for tissues such as epidermis, mucosae, bone marrow, spermatogonia
what stages are within the cell cycle
G0, G1, S, G2, M
where is general outline of mitosis
loosely coiled become visible in mitosis nuclear membrane disintegrates chromosomes line up chromatids separate form new cells during cytokinesis
what are the phases of mitosis
prophase prometaphase metaphase anaphase telophase
what phases are involved in interphase
G1, S, G2
what would the cell look like under a fluorescent microscope in interphase
nucleus, DNA - blue
microtubules within cytoplasm - green
centrosomes - yellow dots
what is the purpose of centrosomes
forming spindles in cell division
what happens during prophase
- the chromosomes condense
- the centrosomes, in form of a pair of centrioles are separating, and spindle fibres are formed
- the nuclear membrane is disintegrating
- a kinetochore forms (complex of proteins that binds to centromere)
what happens during prometaphase
- nuclear envelope breaks down and absorbed by endoplasmic reticulum
- chromosomes condense even more
- chromosomes are connected to microtubules by kinetochores, so chromosomes connected to spindle fibres by kinetochores
- centrosomes moved to poles of cell
- each chromosomes is being captured on centrosome
what happens during metaphase
- the condensed chromosomes are lining up within centre of cell(equator) = at metaphase plate
- spindle fibres are at poles
what happens during anaphase
- each sister chromatids are separated and are now called daughter chromosomes and pulled to polars
what happens during telophase
- nuclear envelope develops around each set of chromosomes
- chromosomes decondense
- cleavage so cell is forming two daughter cells
- spindle fibres disappear
what happens in cytokinesis
cytoplasm divided into two by a contractile ring pof actin and myosin filament to form two daughter cells form
what happens if things go wrong during mitosis, what is this called
nondisjunction = missegregation of chromosomes proper disjunction(good), during anaphase, sister chromatids to separate but in nondisjunction, whole of chromosome goes to one end, so two daughter chromosomes in one cell, other end gets nothing = aneuploidy, an usual amount of chromosomes (2n+ 1) and (2n-1)
when does mitotic nondisjunction occur
during very first post-zygotic division
or later post-zygotic divisoon
what happens during mitotic nondisjunction in first post zygotic division
one of the daughter cells will have an extra copy (47 chromosomes) and one will have a copy less (45 chromosomes)
what is it called when one chromosome is not transferred to a daughter cells and what happens to the cell in first post zygotic division
monosomy
the cell line will then die unless if its X chromosomes then it is viable
what is it called when an extra chromosome is added and continue to develop and what is the result of this in first post zygotic division
undergo mitosis and develop into foetus
leads to a non-mosaic phenotype
this extra copy = downs syndrome (if its chromosome 21)
what happens if mitotic nondisjunction occurs in later post-zygotic division and what is the result of this
first couple of divisions occur normally
the cells that have been dividing normally = 46 chromosomes, and normal phenotypes
so one cell will have 47 chromosomes and the other 45. monosomy occur - cell line usually lost if 45, and if 47 leads to mosaicism, presence of two or more cell lines in an individual(could be throughout body or tissue specific)
What are metaphase spreads
The phase where chromosomes are attached at their centromeres to spindles connected to both poles of the cell
