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Histology > Cell division > Flashcards

Cell division Flashcards

1
Q

Differences between mitosis and meiosis

A
  • In mitosis the daughter cell has same or full number of chromosomes 46 .
  • in meiosis the daughter cell contains half the chromosomes 23 .
  • in mitosis each chromosome splits into two chromatids and each one moves towards each pole of the dividing cell
  • while in meiotic cell division “ meiosis “ the chromosomes arrange themselves in pairs and half of their number 23 moves towards each pole of the dividing cell .
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2
Q

The cell cycle

A
  • Are the changes which occur in the cell during its division ( mitosis ) and during its rest ( interphase ) .
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3
Q

Parts of cell division

A
  • mitosis part

- interphase part

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4
Q

The mitotic part of the cell cycle

A

Is the period of cell division in which each cell divides by mitosis to give two daughter cells

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5
Q

The interphase part of the cell cycle

A

Is the period of cell rest in which the cell is in a resting condition before starting another cell division

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6
Q

The interphase period is divided into

A

G1-phase
S-stage
G2-stage

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7
Q

Gap one stage

A
  • in this stage , the nucleus of each daughter cell has 46 chromatids which are called interphase chromosomes
  • the period of gap one happens between the end of mitosis and the beginning of the next S-Stage
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8
Q

Synthesis stage

A

In this stage - DNA is duplicated through the process of synthesis and replication of DNA molecules
- so that we have 46 identical pairs of chromatids

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9
Q

Gap two stage

A
  • very short period of time lies between the S-Stage and the beginning of mitosis
  • the two chromatin threads of each pair become shorter and thicker —> each pair of the identical chromatids becomes joined together at the centromere to form the chromosomes of the next cell division “ mitosis “ —> the two centrioles are also duplicated into two pairs in this “ gap two stage “ —> now the cell contains 46 pairs of identical chromatids and four centrioles .
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10
Q

Cells of type one according to their cell cycle

A
  • can not divide —> remain outside the cell cycle —> their number is kept constant —> the die cell is rarely replaced by new ones .
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11
Q

The cell of type two according to their cell cycle

A
  • unable to divide —> when they die they are replaced by daughter cells —> arising from stem cells of the same family —> this stem cells are present in the same region
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12
Q

The cell of type three according to their cell cycle

A
  • normally are not divide —> but at a time of need —> they can divide and renew their kind of cells
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13
Q

Give example about type one cells

A

The nerve cells

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14
Q

Give example about type two cells

A

The absorbing and secretory cells of the intestine

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15
Q

Give example about type three cells

A

Liver cells and hormone secreting cells of the endocrine glands

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16
Q

Give the exception from cell division

A

The nerve cells and cardiac cells are exception from cell division

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17
Q

Types of cell division

A
  • Amitosis “ direct cell division “
  • mitosis “ indirect cell division “
  • meiosis “ reduction cell division “
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18
Q

Tell me about Amitosis cell division

A
  • it is a simple division of the nucleus and cytoplasm
  • it occurs in lower animals like amoeba and certain cells of the placenta and embryo
  • it is a process of Asexual reproduction of cells
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19
Q

Tell me about mitosis cell division

A
  • it occurs in the general cells of the body “ somatic cells “
  • the term mitosis —> mitos = thread , osis = process .
  • Example —> process in which threads of chromosomes appear during the stages of mitosis
  • it gives each daughter cells full number of chromosomes
  • the daughter cells will have the same amount of genetic material as the mother cells
20
Q

Tell me about meiosis cell division

A
  • it occurs in germ cells —> which present in the testis and ovary during formation of gametes .
  • it gives each daughter cells the half number of chromosomes “ haploid number “
21
Q

When the cell begins to divide by mitosis certain changes occur in its cytoplasm what they are ?

A
  • a spindle - shaped structure is fused by the microtubules which originate from the cytoplasm —> this spindle plays an important role in bringing the chromosomes at the middle of the dividing cell —> it is also important in the movements of chromosomes towards each end of the elongated dividing cell
22
Q

When the cell begins to divide by mitosis certain changes occur in its nucleus what they are ?

A
  • the chromatin granules change into 46 chromosomes . Each chromosomes is formed of two chromatids which separate from each other during cell division —> each chromosome divides normally in a longitudinal manner into 2 chromatids .
  • the half number of these chromatids moves towards each pole of the dividing cell
  • in each new daughter cell and during its interphase , each chromatid changes into a chromosome , thus 46 chromatids form again the full number of chromosomes which are 46 chromosomes .
23
Q

The period of mitosis

A

The whole process takes from one to two and half hours according to the cell type

24
Q

The prophase period compared to otger phases in mitosis

A

It takes the linger time than any phase —> takes about one and half hours

25
Q

Early prophase in mitosis

A
  • Each pair of centrioles move to one pole of the dividing cell
  • chromosomes formed of two similar elements nts which very closes to each other and called chromatids
  • if the centrioles does not divide in previous gap two stage —> the centrioles duplicate
  • the cytoplasm surrounding each centriole to form ASTRAL RAYS
  • the cytoplasm between the two centrioles also modifies to form SPINDLE FIBERS
  • the nucleoli and nuclear envelop —> disappear
26
Q

Metaphase of mitosis

A
  • the mitotic spindle is well formed and its cytoplasmic microtubules are attached to the centrioles
  • each chromosome in formed of two chromatids which are connected with each other at a point called centromere —> at this centromere there are two rounded bodies called kinetochores —> which form another type of microtubules called chromosomal microtubules
  • the chromosomal microtubules and cytoplasmic microtubules both are forming the mitotic spindle .
  • cytoplasmic microtubules —> arise from cytoplasm —> attached to the centrioles
  • chromosomal microtubules —> arise from kinetochores of chromosomes —> attached to chromosomes .
27
Q

Anaphase of mitosis

A
  • each chromosome ( two chromatids ) split at the centromere by normal longitudinal division —> now we have 92 chromatids
  • half of 92 chromatids move to one pole of the cell and the other 46 to the other pole
28
Q

Telophase of mitosis

A
  • construction begins to develop at mid point of the elongated cell
  • the chromatids “ know as chromosomes “ reach pole of the cell
  • chromosomes become thinner , more elongated and faintly stained
  • nuclear membrane will develop around each set of chromosomes
  • two daughter nuclei are formed
  • process accompanied by cytokinesis or division of cytoplasm
29
Q

The characteristics of meiosis

A
  • occur only in germ cells of the testis and ovary
  • each mother cell give rise to four cells —> each one have haploid number of chromosomes “ 23 “
  • in males , the 4 daughter cells are all viable spermatozoa
  • in females only one of the 4 daughter cells is a viable egg cell , and the other 3 fail to envelop and are known as polar bodies
  • consists of two nuclear divisions
30
Q

meiosis consist essentially of two nuclear division which follow each other tell me about them .

A
  • The first one —> involves the separation of chromosomes leading to the formation of two haploid nuclei ( each one contains 23 chromosomes )
    The second one —> involve the longitudinal separation of chromatids in each one of the previous two haploid nuclei —> leading to the formation of four haploid nuclei ( each nucleus contains 23 chromatids which will be transformed into chromosomes )
31
Q

The prophase of first meiosis

A
  • leptotene phase —> the 46 chromosomes appear as thin threads and long filaments
  • zygotene phase —> 46 chromosomes arranged in 23 pairs of homologous chromosomes called Bivalents, one number is from the father and the other one is from the mother
  • pachytene phase —> chromosomes becomes shorter and thicker —> nucleus appear at this stage
  • diplotene phase —> each chromosomes of each bivalent start to separate from each other —> separation not yet complete —> every two chromosomes remain in contact with on another for some time and touching at certain points known chiasmata —> number of chiasmata generally reduced —> chromosomes continue their separation
  • diakinesis —> in which the nuclear membrane and nucleolus disappear and a mitotic spindle is formed
32
Q

Metaphase of first meiosis

A

The mitotic spindle is well developed across the cell —> the 23 bivalent homologous chromosomes become arranged in the equatorial plane

33
Q

The anaphase of first meiosis

A
  • the bivalent chromosomes separate from one another —> 23 chromosomes move towards the corresponding poles of the dividing cell
34
Q

The telophase of first meiosis

A
  • at each pole of the dividing cell , the 23 chromosomes become surrounded by a nuclear membrane to form the nucleus of the daughter cell
35
Q

Give the exception from cell division

A

The nerve cells and cardiac cells are exception from cell division

36
Q

Types of cell division

A
  • Amitosis “ direct cell division “
  • mitosis “ indirect cell division “
  • meiosis “ reduction cell division “
37
Q

Tell me about Amitosis cell division

A
  • it is a simple division of the nucleus and cytoplasm
  • it occurs in lower animals like amoeba and certain cells of the placenta and embryo
  • it is a process of Asexual reproduction of cells
38
Q

Tell me about mitosis cell division

A
  • it occurs in the general cells of the body “ somatic cells “
  • the term mitosis —> mitos = thread , osis = process .
  • Example —> process in which threads of chromosomes appear during the stages of mitosis
  • it gives each daughter cells full number of chromosomes
  • the daughter cells will have the same amount of genetic material as the mother cells
39
Q

Tell me about meiosis cell division

A
  • it occurs in germ cells —> which present in the testis and ovary during formation of gametes .
  • it gives each daughter cells the half number of chromosomes “ haploid number “
40
Q

When the cell begins to divide by mitosis certain changes occur in its cytoplasm what they are ?

A
  • a spindle - shaped structure is fused by the microtubules which originate from the cytoplasm —> this spindle plays an important role in bringing the chromosomes at the middle of the dividing cell —> it is also important in the movements of chromosomes towards each end of the elongated dividing cell
41
Q

When the cell begins to divide by mitosis certain changes occur in its nucleus what they are ?

A
  • the chromatin granules change into 46 chromosomes . Each chromosomes is formed of two chromatids which separate from each other during cell division —> each chromosome divides normally in a longitudinal manner into 2 chromatids .
  • the half number of these chromatids moves towards each pole of the dividing cell
  • in each new daughter cell and during its interphase , each chromatid changes into a chromosome , thus 46 chromatids form again the full number of chromosomes which are 46 chromosomes .
42
Q

The period of mitosis

A

The whole process takes from one to two and half hours according to the cell type

43
Q

The prophase period compared to otger phases in mitosis

A

It takes the longer time than any phase —> takes about one and half hours

44
Q

Early prophase in mitosis

A
  • Each pair of centrioles move to one pole of the dividing cell
  • chromosomes formed of two similar elements nts which very closes to each other and called chromatids
  • if the centrioles does not divide in previous gap two stage —> the centrioles duplicate
  • the cytoplasm surrounding each centriole to form ASTRAL RAYS
  • the cytoplasm between the two centrioles also modifies to form SPINDLE FIBERS
  • the nucleoli and nuclear envelop —> disappear
45
Q

Metaphase of mitosis

A
  • the mitotic spindle is well formed and its cytoplasmic microtubules are attached to the centrioles
  • each chromosome in formed of two chromatids which are connected with each other at a point called centromere —> at this centromere there are two rounded bodies called kinetochores —> which form another type of microtubules called chromosomal microtubules
  • the chromosomal microtubules and cytoplasmic microtubules both are forming the mitotic spindle .
  • cytoplasmic microtubules —> arise from cytoplasm —> attached to the centrioles
  • chromosomal microtubules —> arise from kinetochores of chromosomes —> attached to chromosomes .
46
Q

Anaphase of mitosis

A
  • each chromosome ( two chromatids ) split at the centromere by normal longitudinal division —> now we have 92 chromatids
  • half of 92 chromatids move to one pole of the cell and the other 46 to the other pole

Histology (5 decks)

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