Cytogenetics

Question 1

mitosis vs interphase
what happens?
visible?
time?

Answer 1

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

Question 2

describe Gap 1 phase
time?
what is required for duplication?

Answer 2

8 hours
nucleus contains 46 chromosome -> cell grows in size and stores ATP -> cells become specialized
RNA and protein synthesis are required

Question 3

G1 time varies on

Answer 3

depending on rate of cell division and specialization

more specialized -> more time

Question 4

S phase time and description

Answer 4

8 hours

1. duplication of DNA do each cell = 46 d chromosome
2. duplication of centrioles

Question 5

Gap 2 time and description

Answer 5

4 hours

1. synthesis of RNA and proteins
2. store energy for mitosis
3. formation of tubulin (for microtubules)
4. error in DNA is corrected

Question 6

G0 phase and types

Answer 6

cells that left cell cycle after specialization

1. non renewing cells - permanent exit
   ex: heart muscles and nerve cells
2. potential renewable cells - can return to continue cycle (transient exit)
   ex: liver cells
3. continuously renewing cells - cannot divide, replaced from stem cells
   ex: blood cells and sperm

Question 7

types of stem cells and ex

Answer 7

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

Question 8

cell death type and results from?

Answer 8

necrosis - results from anoxia, mechanical injury or exposure to toxins
apoptosis - active programmed cell death which is normal after life spam of cell.

Question 9

apoptosis can be

Answer 9

pathological or physiological

Question 10

what happens in cells of necrosis and apoptosis

Answer 10

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

Question 11

nuclei changes in necrosis and apoptosis

Answer 11

pyknosis - nuclei become small, dark, and condensed chromatin
karyorrhexis - nuclei and chromatin are broken into pieces by endonuclease enzyme
karyolysis - nuclei dissolves and disappear

Question 12

fate of necrosis and apoptosis

Answer 12

necrosis - cells degenerate and eaten by macrophages

apoptosis - cells break into large pieces and are eaten by macrophages

Question 13

mitosis

Answer 13

division to produce 2 daughter cells

Question 14

mitosis - prophase
what happens to chromosome?
what disappears?
what 2 other things occur?

Answer 14

chromosome become shorter, thicker, darker
nucleoli disappear
nuclear envelope disappear
centrioles move to opposite poles
microtubules form spindle

Question 15

mitosis - metaphase

Answer 15

chromosome line in middle -metaphase plate

kinetochore develops for attachment of microtubules

Question 16

microtubules arising from MTOC are:

Answer 16

cytoplasmic: continuous for elongation of cell
chromosomal: non continuous and attached to kinetochores in equatorial plane
astral: star like around centrioles

Question 17

mitosis - anaphase

Answer 17

each d chromosome splits forming 2 sister chromatid due to pulling of microtubules and migrate to opposite sides

Question 18

mitosis - telophase

Answer 18

cleavage furrow develops in middle and grows until cells are divided.
46 chromosome length and nuclear envelope and nucleoli come back.

Question 19

meiosis

what phase does it lack?

Answer 19

diploid cells undergo 2 divisions to produce haploid germ cells
no S phase in between divisions

Question 20

prophase 1 of meiosis

time

Answer 20

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

Question 21

metaphase 1 of meiosis

Answer 21

the 23 bivalent align as pairs in middle and attach to microtubules of mitotic spindle

Question 22

anaphase 1 of meosis

Answer 22

bivalent chromosomes separate and go to opposite sides of cell

Question 23

telophase 1 of meosis

Answer 23

two daughter cells are formed and each daughter cell has 23d chromosomes

Question 24

second meiotic division is similar to… and has a short

Answer 24

mitosis , interphase

Question 25

prophase 2 of meiosis

Answer 25

chromosomes becomes shorter and thicker and mitotic spindle appears

Question 26

metaphase 2 of meiosis

Answer 26

23 d chromosome aligned at middle (equatorial plate)

Question 27

anaphase 2 of meiosis

Answer 27

each d chromosome splits at centromere into 2 chromatids which move to opposite poles of cells

Question 28

telophase 2 of meiosis

Answer 28

separation and result is cells with haploid number

Question 29

mitosis vs meiosis

site and number of divisions

Answer 29

mitosis - somatic cells & single division

meiosis - germ cells & 2 divisions w/o S phase

Question 30

mitosis vs meiosis

crossing over

Answer 30

mitosis- no crossing over

meiosis - crossing over

Question 31

mitosis vs meiosis

seperation

Answer 31

mitosis - divides into 2 chromatids

meiosis - divides into bivalents in first

Question 32

mitosis vs meiosis

daughter cells

Answer 32

mitosis - 2 somatic cells with diploid # of identical chromosomes
meiosis - 4 germ cells with different haploid number

Question 33

s-chromosome / chromatid

Answer 33

at G1 stage of interphase and single thread

Question 34

d chromosome

Answer 34

at S stage and double thread

Question 35

during late prophase and metaphase

Answer 35

each chromosome is formed of 2 chromatids

Question 36

centromere

Answer 36

connects 2 chromatids to make chromosome and divides d chromosome into short arm (p) and long arm (q)

Question 37

kinetochords

Answer 37

2 proteins located at centromere to which spindle fibers are attached during cell division

Question 38

each chromatid is coiled around

Answer 38

histone and non histone proteins

Question 39

karyotyping

Answer 39

study of number and type of chromosome according to length and position of centromere

Question 40

karyotyping technique
whats best to use?
how are the cells prepared?
how are they organized and studied?

Answer 40

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

Question 41

karyotyping banding technique

Answer 41

can differentiate chromosomes by staining genes with different colors

Question 42

classification of chromosome - according to gene content

Answer 42

autosomes - 22 identical pairs (somatic)

sex- one pair

Question 43

classification of chromosome - position of centromere

Answer 43

metacentric - centromere @ middle 
p=q
submetacentric - between centre and end 
acrocentric - centromere very close to end 
telocentric - terminal @ end

Question 44

satellites

Answer 44

small masses of chromatin attached to short arm by narrow stalk

Question 45

classification of chromosome - according to length

how are X & Y grouped?

Answer 45

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

Question 46

barr body

tests on?

Answer 46

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

Question 47

clinical importance of barr body or chromosomal examination

Answer 47

1. diagnosis of sex in cases of hermaphroditism
2. identical of foetal sex
3. diagnosis of sex chromosome abnormalities
4. diagnosis of structural abnormalities
5. diagnosis of numerical abnormalities
6. medico- in forensic medicine