Cytogenetics Flashcards
mitosis vs interphase
what happens?
visible?
time?
mitosis - cell divides into 2 daughter cells
visible with microscope
lasts for short period
interphase - period between two divisions
not visible with microscope
lasts long time
describe Gap 1 phase
time?
what is required for duplication?
8 hours
nucleus contains 46 chromosome -> cell grows in size and stores ATP -> cells become specialized
RNA and protein synthesis are required
G1 time varies on
depending on rate of cell division and specialization
more specialized -> more time
S phase time and description
8 hours
- duplication of DNA do each cell = 46 d chromosome
- duplication of centrioles
Gap 2 time and description
4 hours
- synthesis of RNA and proteins
- store energy for mitosis
- formation of tubulin (for microtubules)
- error in DNA is corrected
G0 phase and types
cells that left cell cycle after specialization
- non renewing cells - permanent exit
ex: heart muscles and nerve cells - potential renewable cells - can return to continue cycle (transient exit)
ex: liver cells - continuously renewing cells - cannot divide, replaced from stem cells
ex: blood cells and sperm
types of stem cells and ex
pluripotential/multipotential stem cell - can make more than one type of specialized cells
ex: blood cells and cells lining GIT
unipotential stem cell - can only produce one type of specialized cell
ex: male germ cells
cell death type and results from?
necrosis - results from anoxia, mechanical injury or exposure to toxins
apoptosis - active programmed cell death which is normal after life spam of cell.
apoptosis can be
pathological or physiological
what happens in cells of necrosis and apoptosis
necrosis - cells and organelles swell and burst, releasing their content into extra cellular space
apoptosis - do not swell, they shrink and and decrease in size
nuclei changes in necrosis and apoptosis
pyknosis - nuclei become small, dark, and condensed chromatin
karyorrhexis - nuclei and chromatin are broken into pieces by endonuclease enzyme
karyolysis - nuclei dissolves and disappear
fate of necrosis and apoptosis
necrosis - cells degenerate and eaten by macrophages
apoptosis - cells break into large pieces and are eaten by macrophages
mitosis
division to produce 2 daughter cells
mitosis - prophase
what happens to chromosome?
what disappears?
what 2 other things occur?
chromosome become shorter, thicker, darker nucleoli disappear nuclear envelope disappear centrioles move to opposite poles microtubules form spindle
mitosis - metaphase
chromosome line in middle -metaphase plate
kinetochore develops for attachment of microtubules
microtubules arising from MTOC are:
cytoplasmic: continuous for elongation of cell
chromosomal: non continuous and attached to kinetochores in equatorial plane
astral: star like around centrioles
mitosis - anaphase
each d chromosome splits forming 2 sister chromatid due to pulling of microtubules and migrate to opposite sides
mitosis - telophase
cleavage furrow develops in middle and grows until cells are divided.
46 chromosome length and nuclear envelope and nucleoli come back.
meiosis
what phase does it lack?
diploid cells undergo 2 divisions to produce haploid germ cells
no S phase in between divisions
prophase 1 of meiosis
time
males - lasts 22 days
females - 12-45 years to complete
-chromosomes are 23 pairs (bivalents)
-bivalents become shorter and thicker and appear like tetrads (4 chromatids)
- crossing over occurs
- begin to seperate
- nucleolus and nuclear envelope dissapear
metaphase 1 of meiosis
the 23 bivalent align as pairs in middle and attach to microtubules of mitotic spindle
anaphase 1 of meosis
bivalent chromosomes separate and go to opposite sides of cell
telophase 1 of meosis
two daughter cells are formed and each daughter cell has 23d chromosomes
second meiotic division is similar to… and has a short
mitosis , interphase
prophase 2 of meiosis
chromosomes becomes shorter and thicker and mitotic spindle appears
metaphase 2 of meiosis
23 d chromosome aligned at middle (equatorial plate)
anaphase 2 of meiosis
each d chromosome splits at centromere into 2 chromatids which move to opposite poles of cells
telophase 2 of meiosis
separation and result is cells with haploid number
mitosis vs meiosis
site and number of divisions
mitosis - somatic cells & single division
meiosis - germ cells & 2 divisions w/o S phase
mitosis vs meiosis
crossing over
mitosis- no crossing over
meiosis - crossing over
mitosis vs meiosis
seperation
mitosis - divides into 2 chromatids
meiosis - divides into bivalents in first
mitosis vs meiosis
daughter cells
mitosis - 2 somatic cells with diploid # of identical chromosomes
meiosis - 4 germ cells with different haploid number
s-chromosome / chromatid
at G1 stage of interphase and single thread
d chromosome
at S stage and double thread
during late prophase and metaphase
each chromosome is formed of 2 chromatids
centromere
connects 2 chromatids to make chromosome and divides d chromosome into short arm (p) and long arm (q)
kinetochords
2 proteins located at centromere to which spindle fibers are attached during cell division
each chromatid is coiled around
histone and non histone proteins
karyotyping
study of number and type of chromosome according to length and position of centromere
karyotyping technique
whats best to use?
how are the cells prepared?
how are they organized and studied?
use leucocytes (white blood cells)
cells are divided and stopped at metaphase
they are then photographed and matched to pairs and arranged by length.
they are studied using software programs
karyotyping banding technique
can differentiate chromosomes by staining genes with different colors
classification of chromosome - according to gene content
autosomes - 22 identical pairs (somatic)
sex- one pair
classification of chromosome - position of centromere
metacentric - centromere @ middle p=q submetacentric - between centre and end acrocentric - centromere very close to end telocentric - terminal @ end
satellites
small masses of chromatin attached to short arm by narrow stalk
classification of chromosome - according to length
how are X & Y grouped?
chromosomes are numbered 1-22 then grouped into descending order of length by A,B,C,D,E,F,G
X and Y are either alone or X in group C and Y in group G
barr body
tests on?
test on neutrophil and leucocytes (white blood cells)
represents inactive coiled dark stained X chromosome present in female while the active X is not shown
clinical importance of barr body or chromosomal examination
- diagnosis of sex in cases of hermaphroditism
- identical of foetal sex
- diagnosis of sex chromosome abnormalities
- diagnosis of structural abnormalities
- diagnosis of numerical abnormalities
- medico- in forensic medicine
