Topic 11: Mitosis

Question 1

what is mitosis

Answer 1

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)

Question 2

what is M phase made up of

Answer 2

nuclear division (mitosis)
cellular division (cytokinesis)

Question 3

how many rounds of mitosis are there during early development

Answer 3

50

Question 4

why is mitotic growth necessary

Answer 4

for tissues such as epidermis, mucosae, bone marrow, spermatogonia

Question 5

what stages are within the cell cycle

Answer 5

G0, G1, S, G2, M

Question 6

where is general outline of mitosis

Answer 6

loosely coiled
become visible in mitosis
nuclear membrane disintegrates
chromosomes line up
chromatids separate
form new cells during cytokinesis

Question 7

what are the phases of mitosis

Answer 7

prophase
prometaphase
metaphase
anaphase
telophase

Question 8

what phases are involved in interphase

Answer 8

G1, S, G2

Question 9

what would the cell look like under a fluorescent microscope in interphase

Answer 9

nucleus, DNA - blue
microtubules within cytoplasm - green
centrosomes - yellow dots

Question 10

what is the purpose of centrosomes

Answer 10

forming spindles in cell division

Question 11

what happens during prophase

Answer 11

• 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)

Question 12

what happens during prometaphase

Answer 12

• 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

Question 13

what happens during metaphase

Answer 13

• the condensed chromosomes are lining up within centre of cell(equator) = at metaphase plate
• spindle fibres are at poles

Question 14

what happens during anaphase

Answer 14

• each sister chromatids are separated and are now called daughter chromosomes and pulled to polars

Question 15

what happens during telophase

Answer 15

• nuclear envelope develops around each set of chromosomes
• chromosomes decondense
• cleavage so cell is forming two daughter cells
• spindle fibres disappear

Question 16

what happens in cytokinesis

Answer 16

cytoplasm divided into two by a contractile ring pof actin and myosin filament to form two daughter cells form

Question 17

what happens if things go wrong during mitosis, what is this called

Answer 17

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)

Question 18

when does mitotic nondisjunction occur

Answer 18

during very first post-zygotic division

or later post-zygotic divisoon

Question 19

what happens during mitotic nondisjunction in first post zygotic division

Answer 19

one of the daughter cells will have an extra copy (47 chromosomes) and one will have a copy less (45 chromosomes)

Question 20

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

Answer 20

monosomy

the cell line will then die unless if its X chromosomes then it is viable

Question 21

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

Answer 21

undergo mitosis and develop into foetus
leads to a non-mosaic phenotype
this extra copy = downs syndrome (if its chromosome 21)

Question 22

what happens if mitotic nondisjunction occurs in later post-zygotic division and what is the result of this

Answer 22

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)

Question 23

What are metaphase spreads

Answer 23

The phase where chromosomes are attached at their centromeres to spindles connected to both poles of the cell