Variation Checkpoint
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- Somatic and Gametic cells
SOMATIC CELLS -body cells
- -contain the DIPLOID [2n] chromosome number.
- -produced through MITOSIS.
- -examples: muscle cell, nerve cell, stomach cell.
GAMETES -sex cells
- -contain the HAPLOID [n] chromosome number.
- -produced through MEIOSIS.
- -examples: sperm cell and egg cell
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Phases of the Cell Cycle
The cell cycle consists of
- Mitotic (M) phase (mitosis and cytokinesis)
- Interphase (cell growth and copying of chromosomes in preparation for cell division)
CELL DIVISION
- INTER PHASE
- MITOSIS
- CYTOKINESIS
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Interphase (about 90% of the cell cycle) can be divided into subphases:
G₁ phase ("first gap") or ("growth")
S phase ("DNA synthesis")
G₂ phase ("second gap") or ("growth")
• The cell grows during all three phases, but chromosomes are duplicated only during the S phase
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- Mitosis is conventionally divided into five phases:
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis is well underway by late telophase
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It is because of the meristematic cells that are situated in the tip of the roots that render the most
desirable and suitable raw material to study the different stages of mitosis. Onion is a monocot
plant. Monocotyledonous plants possess large chromosomes that are clearly visible. Hence, their
root tips are used. The period of time taken for mitosis varies as it is dependent on the cell type and
type of species
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تجربة الانقسام المايتوزي في البصل
Procedure Of The Experiment
1. Place an onion on a tile
2. With the help of a sharp blade, carefully snip the dry roots of
the onion
3. Place the bulbs in a beaker containing water to grow the root
tips
It may take around 4 to 6 days for the new roots to grow and
appear
4. Trim around 3 cm of the newly grown roots and place them in a
watch glass
5. With the help of forceps, shift it to a vial holding freshly
prepared aceto-alcohol i.e., a mixture of glacial acetic acid and
ethanol in the ratio 1:3.
6. Allow the root tips to remain the vial for one complete day
7. With the help of forceps, pick one root and set in on a new
glass slide
8. With the help of a dropper, allow one drop of N/10 HCl to come
in contact with the tip of the root. Additionally, add around 2 to
3 drops of the acetocarmine stain.
.
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9 Heat is lightly on the burner in such a way that the stain does not dry up.
.
10 Excessive stain can be carefully treated using filter paper
.
The more stained part of the root tip can be trimmed with the 11 help of a blade.
.
Discard the lesser stained part while retaining the more 12
stained section. Then
Add a droplet of water to it
13.With the help of a needle, a coverslip can be mounted on it
14.Gently tap the coverslip with an unsharpened end of a needle in order for the
meristematic tissue of the root tip present under the coverslip to be squashed
properly and to be straightened out as a fine cell layer
The onion root tip cells’ slide is now prepared and ready to be examined for
different stages of mitosis
Observe and study mitosis by placing the slide under the compound microscope.
Focus as desired to obtain a distinct and clear image
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تجربة الانقسام المايتوسي بختصار
1- Cut fresh Onion roots and keep in water
2- hydrolysis : take some roots in watchglass
3- take 10% HCl in a test tube and gently warm using spirit lamp
4- pour warm HCl in a watchglass and wait for 10 mins
5- after 10 mins : wash room tips with water 3-4 times
6- staining : take one root on slide
7- take only milky white portion of tip then discard remining part
8- put a drop (2-3 ) of acetocarmine on portion of tip
9- wait until mike whitw tip turns red
10 - place a coverslipe on sample
11 - observe under microscope
12 - mitosis Observe and study mitosis by placing the slide under the compound microscope
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