Biology Chapter 10 Cell Cycle And Cell Division

1. First gap phase (G₁ phase) or presynthetic phase.

2. Synthetic phase (S phase)

3. Second gap phase (G₂ phase) or Mitotic phase (M phase)

4. Cell division phase or Mitotic phase (M phase).

The G₁, S and G₂ phases together constitute the Interphase. This phase takes about 95% of the duration of cell cycle. The mitotic or M phase only lasts for about an hour. 

1. G₁ phase. This stage starts from the birth of the daughter cell and ends upto the time when the cell begins to synthesis of DNA. It is the phase of initial growth in which RNA and proteins are synthesised. Its duration varies from 6 to 8 hours.

2. S phase. It is the period of synthesis of DNA. It lasts for 5-6 hours.

Fig. Cell cycle

3. G₂ phase. During this phase the centrioles, mitochondria, golgi bodies and other cytoplasmic organelles are doubled. Proteins are synthesised for the formation of astral rays and spindle and energy is stored for the cell division or M phase. The duration of this stage starts from the end of S phase upto the beginning of M phase. It lasts for 4-8 hours.

4. M phase or mitosis. It is the phase when the cell division takes place and this process gives rise to two daughter cells.  collectively form the cell cycle.

1. It is an equational division. The daughter cells are identical to each other and also to the parent cell in genetic constitution.

2. Mitosis helps in the survival of a species and continuation of its race. It gives a complete set of genetic information to each cell.

3. Mitosis is related to the growth of an individual from zygote to adult stage.

4. It helps in repairing of cells, healing of wounds and regeneration of body cells. 

5. It helps in maintaining a specific nucleocytoplasmic ratio in a cell.

1. The ribonuclease enzyme acts as poison at prophase.

2. Mustard gas causes fragmentation and agglutination of chromosomes.

3. Colchicine inhibits the formation of mitotic spindle. 

1. Prophase II. It occurs immediately after cytokinesis of meiosis I. The nuclear membrane disaapars and chromosomes become compact.

2. Metaphase II. The chromosomes arrange themselves on the equator. Each chromosome is attached to the spindle fibres of opposite poles by its centromeres. The spindle microtubules from the opposite poles attach to the kinetochores of sister chromatids.

3. Anaphase II. The centromere of each chromosome divides into two sister chromatids. Thus two chromatids of each chromosome move towards opposite poles. 

4. Telophase II. The group of young chromosomes at each pole arranges itself into a daughter nucleus. The nuclear membrane is formed. Nucleoli appear and spindles disappear. takes place resulting in the formation of four daughter cells. 

2. Formation of spores. Meiosis produces spores in plants for asexual reproduction.

3. Maintenance of chromosome number. Meiosis reduces the chromosome number in the gametes so that fertilization may restore the original diploid number in the zygote.

4. Introduction of variations. Meiosis provides a chance for the formation of new combinations of alleles and chromosomes. This brings about variations which cause evolution. The new combinations of alleles are produced by crossing-over in prophase-I.

1. The gametic fusion takes place at the time of fertilisation when sperm and ovum fuse to form a diploid zygote.

2. The zygote is divided by mitotic division during its embroynic life and post embryonic life to form a well developed individual.

3. A mature individual produces gametes by gametogensis. Reductional division takes place at this stage and results in the formation of haploid gametes.

Example. If a parent cell has 16 chromosomes then in daughter cells due to meiotic division number of chromosomes is reduced to eight.

Mitosis. It is called equational division because number of chromosomes and amount of DNA in daughter cells remain equal to parent cells.

Example. If a parent cell has 18 chromosomes, then in daughter cells formed by mitosis have each 18 chromosomes. 

Significance.-  At chiasmata crossing over occurs in pachytene stage. The crossing over brings variations which are raw material of evolution.

Mitosis in Animal Cell

2. Bivalent : A pair of homologous chromosomes is called bivalent.

3. Chiasmata : It is point in a tetrad where crossing over occurs.

1. Male bees, wasps and ants are haploid as they are produced from unfertilized eggs. 

2. Synergids and antipodal cells do not divide.

Whereas, the primary oocyte divide to form ootid and polar bodies of unequal size. 

Interphase is the resting stage of the cell cycle. It covers 95% of the total duration of a cell cycle. It involves a series of changes that prepare a cell for division. It is the period during which the cell experiences growth and DNA replication in an orderly manner. Interphase is divided into three phases.

(i) G₁ phase

(ii) S phase

(iii) G₂ phase

G₁ phase - It is the interval between mitosis and initiation of DNA replication. It is the stage during which the cell grows and prepares its DNA for replication. In this phase, the cell is metabolically active but there is no replication of the DNA.

S phase - It is known as the synthesis phase as it is the stage during which DNA synthesis occurs. In this phase, the amount of DNA (per cell) doubles, but the chromosome number remains the same.

G₂ phase - In this phase, the cell continues to grow and prepares itself for the division. The proteins and RNA required for mitosis are synthesised during this stage.

The G₀ or quiescent phase is the inactive stage that some cells enter in the adult animals. the stage is characterised by cells that do not exhibit division or proliferation but are metabolically active. They only proliferate when called on to do so depending on the requirement of the organism. 

Meiosis is the reduction division the reduction in the amount of genetic material.

Significance of meiosis

1. Meiosis maintains the chromosome number from generation to generation. It reduces the chromosome number to half so that the process of fertilisation can restore the original number in the zygote.

2. It has an evolutionary importance as it allows variations to occur. The process of cross-over and the random distribution of homologous chromosomes between daughter cells result in variation in the genetic make-up of the cells. Variations play an important role in evolution.

3. Chromosomal mutations are brought about by the introduction of certain inheritable changes which may be advantageous for an individual.

A.

spindle fibres, centrioles and cilia

Microtubules are structures present in cilia, flagella, centrioles and spindle fibres. They are also the part of fibres found in cytoskeleton. 

A.

polyploidy

Polyploid cells have a chromosome number that is more than double the haploid number.

C.

Synapsis

Synapsis is pairing of homologous chromosomes. It occurs during zygotene stage of meiosis

A.

kinetochore of the chromosome

Spindle fibres attach to kinetochores of chromosomes during cell division. They help the chromosomes to get separated to the two daughter cells, towards opposite poles. 

D.

pachytene

Crossing over takes place in pachytene stage. 

C.

bivalent

Homologous chromosomes pair up. This process is called synapsis. Each pair is called bivalent. Chromosomes line up around the equator of the spindle, attached by their centromeres to the spindle fibres, which are microtubules. The microtubules forming spindles can be of two types, i.e., kinetochore-microtubule and non-kinetochore microtubule.
Axoneme is the central core of a cilium of flagellum consisting of a central pair of filaments surrounded by nine other pairs. The equatorial plate is the plane located midway between the poles of a dividing cell during the metaphase stage of mitosis or meiosis. It is formed from the migration of the chromosome to the centre of the spindle.

A.

Meiocyte

In diploid organisms, specialised cells called meiocytes(gamete mother cell) undergo meiosis. Conidia and gemmules are asexual reproductive structures found in penicillium and sponge respectively. Megaspores are female gametes in plants, which undergo sexual reproduction.

A.

 T- lymphocytes

T - lymphocyte receptors can recognise the only antigen that bound to cell membrane proteins these lymphocytes mediates CMI (cell-mediated immunity). B - lymphocytes are the major effector molecules of humoral immunity. Erythrocytes are red blood cells. Thrombocytes or platelets secrete factors that are involved in the vascular repair.

A.

Telophase is the reserve of prophase. The chromosome that has reached their respective polar decondense and their individually. Late anaphase is characterised by centromeres split and chromatid moves to opposite poles. Cytokinesis is processed in which cell itself is divided two daughter cells.

B.

(b), (a) (c), (d)

The correct sequence of events of meiosis are:
Synapsis in zygotene Crossing over in pachytene Terminalisation of chiasmata in diplotene  Disappearance of nucleolus in diakinesis.

D.

G₂ and M

During the S or synthetic phase, the DNA content double, i,e, from 2C to 4C for all diploid cells. The G₂ phase follows the S-phase and is called second growth phase or pre-mitotic gap phase. In G₂ phase the synthesis of DNA stops, therefore, the DNA level remains 4C if initial was 2C
However, the formation of RNA and protein continues as they are required for the multiplication of cell organelles, spindle formation and cell growth. This amount becomes, half (i.e,) 2C only during anaphase (in mitosis) when chromosomes separate.

B.

fertilization

In human females, meiosis-II is not completed until fertilisation. Secondary oocyte is arrested in metaphase-II stage until sperm cell contacts plasma membrane of the oocyte and completes meiosis II resulting in release of ovum. 

C.

prophase-I

The pachytene stage of prophase I of meiosis I is characterized by the appearance of recombination nodules, the sites at which crossing over occurs between non-sister chromatids of the homologous chromosomes. Crossing over is the exchange of genetic material between two homologous chromosomes. It is also an enzyme-mediated process and the enzyme involved is called recombinase.

A.

amount of DNA dobles in each cell

S-phase is the synthesis phase in which the cell synthesis a replica of its gerome, i.e., DNA replication occurs by DNA polymerase. 
DNA replication along with the synthesis of histone proteins results in the duplication of chromosomal material i.e., amount of DNA doubles in each cell. 
Amount of DNA remains unchanged during G₁ pahse or post mitotic gap and /or G₂ phase pre mitotic phase.

A.

Prophase-I during meiosis

The figure shows zygotine stage of prophase-I of meiosis-I. During this stage, bivalent chromosomes clearly appear as tetrads, Pachytene stage is characterized by the appearance of recombination nodules, the sites at which crossing over (exchange of genetic material) occurs between non-sister chromatids of the homologous chromosomes.

C.

anaphase I

In anaphase - I of meiosis homologous chromosomes separate and pass towards different poles of the spindle creating two haploid sets of chromosomes.
During anaphase-II of meiosis centromere of two chromatids of a chromosome separate. The separated chromatids become independent daughter chromosome.

C.

twice the number of chromosomes and four times the amount of DNA

In general a gamete contains 'n' number of chromosomes (haploid) and 'x' amount of DNA. In comparison to the gamete, an (diploid) somatic cell usually have 2n number of chromosomes and 2x amount of DNA. But, after the cell enters and complete the 'S'-phase of its cell cycle, the DNA content of the cell becomes double (due to its duplication). However, the number of chromosomes remains the same. Hence, the somatic cell that has undergone and completed its 'S' phase of cell cycle will have twice the number of chromosomes and four times the DNA content.
                         

A.

63

The outermost cell layer of the endosperm (3n) of seed is called aleurone layer. Since the cells of aleurone layer are triploid, the number of chromosomes would be = 63, as root tip cells (2n) has 42 chromosomes.

C.

chromosomes move to the spindle equator and get aligned along equatorial plate in metaphase

In metaphase of mitosis, spindle fibres attach to kinetochore of chromosomes. Chromosomes are moved to spindle equator and get aligned along meta phasic plate through spindle fibres to both poles.

C.

Kinetochores

Kinetochores ar small disc -shaped proteinous structures present at the surface of the centromere. These structures serve as the sites of attachment of spindle fibres to the chromosomes that are moved into position at the centre of the cell.

D.

early prophase

In mitosis, prophase is the longest phase of karyokinesis.In early prophase, nuclear membranes, nucleolus start disintegrating. cells cytoskeleton, Golgi complex, ER, etc disappear.

C.

Late anaphase - Prophase

Late anaphase is characterised by following events;
i) Centromeres split and chromatids separate.
ii) Chromatids move to opposite poles.
Prophase is characterised by centriole separation.

D.

n = 21  and x = 7

The basic (x) number of chromosome of hexaploid wheat is 7  and haploid (n) number is 21.

B.

24

Synergids are two, short-lived, haploid cells lying close to the egg in nature embryosac of flowering plant ovule. While the endosperm is a triploid tissue formed after triple fusion. Thus, if the synergids have 8 chromosomes, the aleurone layer (part of endosperm) will have just triple of that of chromosomes in the synergids i.e, 24 chromosomes.

B.

Condensation - nuclear membrane disassembly
-arrangement at equator - centromere
division - segregation - telophase

The correct sequence of events during mitosis would
be as follows
(i) Condensation of DNA so that chromosomes become visible occurs during early to mid-prophase.
(ii) Nuclear membrane disassembly begins at late prophase or transition to metaphase.
(iii) Arrangement of chromosomes at equator occurs during metaphase, called congression.
(iv) Centromere division or splitting occurs during anaphase forming daughter chromosomes.

D.

Chlamydomonas

C.

Chromosomes will not segregate

Anaphase Promoting Complex (APC) is a protein necessary for separation of daughter chromosomes during anaphase. If APC is defective then the chromosomes will fail to segregate during anaphase.

C.

Prior to fission

DNA replication in bacteria occurs prior to fission. Prokaryotes do not show well marked S-phase due to their primitive nature

C.

Polytene chromosomes – Oocytes of amphibians

Polytene chromosomes are found in salivary glands of insects of order Diptera.

C.

Phospholipid synthesis

Phospholipid synthesis does not take place in rough endoplasmic reticulum (RER). Smooth endoplasmic reticulum are involved in lipid synthesis.

D.

Pseudopodia are locomotory and feeding structures in Sporozoans

Pseudopodia are locomotory structures in sarcodines (Amoeboid).

C.

Synthesis of histone proteins

Post-mitotic gap phase is characterised by all except the synthesis of histone proteins. Histone proteins are synthesised in S-phase. S-phase is called invisible phase of the cell cycle as replicated chromosomes are not visible at this stage.

B.

Metaphase-I of meiosis

The independent assortment of the gene occurs due to the orientation of chromosomes at late metaphase - I of meiotic cell division at the time of gamete formation.

C.

Anaphase-I, anaphase-II

In anaphase-I and II chromosomes become shorter and thicker and migrate towards opposite poles of the cell. In case of non-disjunction of chromosomes, an extra copy of a chromosome will be present in the cell.

C.

The longest phase of cell cycle in G₁ where these rapid growths and metabolic activity, followed by S phase for DNA synthesis and replication then G₂ phase for preparation of cell division and lastly mitotic phase.

therefore, Ratio is 9:5:3:1

A.

Decondensation from chromosome and reassembly of the nuclear lamina

At telophase stage, nuclear membrane vesicles associate with the surface of individual chromosomes and fuse to reform the nuclear membranes, which partially enclose clusters of chromosomes before coalescing to reform the complete nuclear envelope. During this process, the nuclear pores reassemble and the dephosphorylated reassociate to form the nuclear lamina) One of the lamina proteins (lamina-B) remains with the nuclear membrane fragments throughout mitosis and may help nucleate assembly. After the nucleus reforms, the pores pump in nuclear proteins, the chromosome decondense and RNA synthesis resume, causing the nucleolus to reappear.

C.

Lytic

When bacteriophage infects a bacterium, it entirely depends on the host for its multiplication. It utilises the host machinery for replication and produce a large number of progeny phage particles. The bacterium cell undergoes lysis and dies to liberate a large number of these phage particles, which are each ready to start another cycle by infecting new bacterial cell. This cycle is known as lytic cycle.

A.

homologous chromosomes are seperated

Meiotic division occurs in reproductive system or germ cells. After meiosis, four haploid cells are present which are not identical to their parents. Homologous chromosomes form bivalent by pairing and each of them is seperated. They move towards the opposite poles of the spindle fibres. Each daughter cell receives a haploid set of chromosomes.

A.

RNA and proteins are synthesised

Cell division has two phases:

(a) Karyokinesis- Nucleus division.

It is further divided into-

   (i) Interphase is a resting phase and consists of G₁, S and G₂ phase.

  (ii) M- phase represnts the phase of actual division

(b) Cytokinesis- Cytoplasm division.

A.

Metaphase

Metaphase in both mitosis and meiosis is characterized by the arrangement of chromosomes on the spindle fibres at the equatorial plate.

Prophase is the longest phase. In this phase, chromatin of nucleus becomes condensed forming chromosomes.

Anaphase is the phase where the separation of chromatids takes place. It moves in the opposite direction towards the pole and is the shortest phase of all.

Telophase is the last phase. In this phase, chromatin network are reformed, nuclear membrane and nucleolus reappears.

A.

tubulin

The mitotic spindle is a highly dynamic molecular machine composed of tubulin, motors and other molecules. It assembles around the chromosomes and distributes the duplicated genome to the daughter cells during mitosis. 

Microtubules are unbranched, hollow, sub- microscopic tubules, which form the structural material of cilia, flagella, basal bodies, centrioles and spindle apparatus. They are built up protofilaments, formed of two related proteins, $\alpha$ and $\beta$- tubulins. 

C.

pachytene

Crossing over, ie, exchange of segments between non- sister chromatids of homologous chromosome occurs in pachytene stage of Prophase- I of Meiosis- I.

B.

7

The number of chromosomes in root cells is 2n while it is n in synergids because it develops by reductional division.

Therefore, the number of chromosomes in synergid cells is 7.

C.

During S-phase

Histone proteins are basic proteins used for the packaging of eukaryotic DNA. Both DNA and histones together comprise of chromatin, forming bulk of eukaryotic chromosomes. There are 5 major kinds of histones- H₁, H_2A, H_2B, H₃ and H₄. 

H₁ histone is used for linking neighbouring chromosomes while others are used as elements of nucleosomes structure. During S- phase of cell cycle, synthesis of histone proteins takes place as the chromosome number gets doubled to that of somatic number.

A.

Ist reductional and IInd equational

The term 'Meiosis' was given by Farmer and Moore (1905). To study meiosis in plants, anther is the best part. 

The process of meiosis involves two division of the genetic material. The first division is called reduction division or Meiosis I as it reduces the number of chromosomes from 46 chromosomes or 2n to 23 chromosomes or n.

Meiosis II is called equational division because it does not reduce chromosome numbers. A nuclear division that maintains the same ploidy level of the cell.

B.

Metaphase

Colchicine, an alkaloid obtained from Colchincum autumnale (Liliaceae), prevents mitosis by inhibiting spindle formation through disruption of microtubules. It is a mitotic poison.

C.

S- phase

S- phase or Synthesis phase is the phase of the cell cycle in which DNA is replicated. It occurs between G₁ and G₂ phase.

During this phase, DNA is replicated and histones are sythesized so that each chromosomes becomes two chromatids.

D.

Farmer and Moore

Farmer and Moore (1905) proposed the term meiosis. Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cells, as in production of gametes and plant spores.

D.

meiotic prophase

Lampbrush chromosomes are a special form of chromoosme found in the growing oocytes of most animals, except mammals. They grow profusely during prophase of meiosis- I.

C.

assessing DNA damage

A checkpoint is one of several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favourable.

C.

assess DNA damage

A checkpoint is one of several points in the eukaryoticcell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable.

A.

interphase in cell of female mammal

Barr body is also known as sex chromatin or X chromatin. Barr body is partially inactivated and development of this facultative heterochromatin occurs in one of the two X chromosomes in interphase nuclei of human female. Any of the two X-chromosomes can become heterochromatin.

B.

interphase

Cell cycle is divided into 2 phases.

(i) Interphase (a period of preparation for cell division)

(ii) M phase (the actual period of cell division).

The interphase cell is metabolically quite active. Interphase is the long nondividing phase further divided into G₁, S and G_2. It occupies 75 to 95% of entire cell division time.

B.

pachytene

Prophase I consists of 5 stages:

(i) Leptotene- Chromosomes become gradually visible.

(ii) Zygotene- Synapsis, pairing of homlogous chromosomes takes place. It results in the formation of bivalents. Also, formation of special proteinaceous structure called synaptonemal complex occur.

(iii) Pachytene- Cells that eneterd this phase results in spiralling, shortening and thickening of the bivalents.

(iv) Diplotene- Dissolution of synaptonemal complex takes place. Also, recombined homologous chromosomes of the bivalents seperate.

(v) Diakinesis- Terminalisation of chiasmata occur in this phase.

D.

maintaining the number of chromosomes

Meiosis is a type of cell division that results in 4 daughter cells each with half the number of chromosomes of the parent cell. It maintains the fixed number of chromosomes in sexually reproducing organisms. It produces haploid gametes by reducing the chromosome number to half. These gametes on fertilization restore diploidy.

D.

anaphase and metaphase

In metaphase, chromosomes align at the metaphase plate and sister chromatids attach to spindle fibres from opposite poles. 

In anaphase, centromeres divide and chromatids move to opposite poles. This is known as the separation of sister chromatids.

B.

kinetochore

As prometaphase ends and metaphase begins, the chromosomes align along the cell equator. Every chromosome has at least two microtubules extending from its kinetochore — with at least one microtubule connected to each pole. At this point, the tension within the cell becomes balanced, and the chromosomes no longer move back and forth. In addition, the spindle is now complete, and three groups of spindle microtubules are apparent. Kinetochore microtubules attach the chromosomes to the spindle pole; interpolar microtubules extend from the spindle pole across the equator, almost to the opposite spindle pole; and astral microtubules extend from the spindle pole to the cell membrane.

C.

interphase

S phase is the early phase of cell cycle. S phase (Synthesis Phase) is the phase of the cell cycle in which DNA is replicated, occurring between G₁ phase and G₂ phase. Since accurate duplication of the genome is critical to successful cell division, the processes that occur during S-phase are tightly regulated and widely conserved.

A.

tetrad

A bivalent, sometimes referred to as a tetrad, is the association of a pair of homologous chromosomes physically held together by at least one DNA crossover. This physical attachment allows for alignment and segregation of the homologous chromosomes in the first meiotic division.

D.

Pachytene

Pachytene is a stage of first meiotic division in which the chromosomes appear further thickened due to coiling and divides longitudinally into two sister chromatids.

A.

G_1 $\to$S $\to$G₂ $\to$ M $\to$G₁

The basic parts of cell cycle are interphase and M-phase or dividing phase. The interphase is metabolically the most active stage and divided into G₁, S and G₂ phases. The correct sequence of phases in cell cycle is

G₁ $\to$S $\to$G₂ $\to$M $\to$G₁

D.

Interphase

Interphase is a phase of cell cycle where cell prepares itself for division. It consists of 3 phases: G₁ phase, S phase and G₂ phase.

During S or Synthesis phase, all the chromosomes get replicated. Each chromosome consists of two sister chromatids.

In eukaryotic DNA, histone and non- histone proteins are known as chromatin. It consists of thread- like structures known as chromosomes. Hence, the replication of DNA in the chromosomes initiates in S- phase of interphase.

C.

Anaphase

'Anaphase', is the stage of mitosis after the metaphase when replicated chromosomes are split and the daughter chromatids are moved to opposite poles of the cell. Chromosomes also reach their overall maximum condensation in late anaphase, to help chromosome segregation and the re-formation of the nucleus.

C.

S - phase

Cell cycle is a series of events that take place in a cell leading to duplication of its DNA and division of cytoplasm and organelles to produce two daughter cells. 

Interphase has 3 stages: G₁ phase, S- phase and G₂ phase. S or synthesis phase is a the stage where DNA starts replication.

B.

G₂- phase

Cell division can not be stopped G₂ phase of the cell cycle.

C.

suspend cell cycle

The G0 phase or resting phase is a period in the cell cycle in which cells exist in a quiescent state. G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle.

A.

prophase- I

Meiosis is a division necessary for the formation of gametes in animals and spores in plants. Prophase- I is longest phase of meiosis and composed 5 sub phases which are leptotene, zygotene, pachytene, diplotene and diakinesis.

C.

Pachytene

In pachytene substage of meiosis- I the paired homologous chromosomes divide into two sister chromatids. Thus, each bivalent is composed of four chromatids and known as tetrad. 

B.

G₁ - S - G₂ - M

The complete cell cycle contains a sequence of phases which are

(a) Interphase which is further subdivided into G₁-phase or postmitotic gap, S-phase or synthesis phase and G₂-phase or premitotic gap respectively 

(b) Dividing phase or M-phase (mitotic or meiotic phase) which comprises karyokinesis and cytokinesis.

So, the correct sequence of phases in cell cycle is

G₁ $\to$S $\to$G₂ $\to$M

C.

bivalent

Synapsis is the pairing of homologous chromosomes. Each pair is called bivalent. Chromosomes line up around the equator of the spindle, attached by their centromeres to the spindle fibres, which are microtubules. The microtubules forming spindles can be of two types, i.e., kinetochore microtubule and non-kinetochore microtubule. 

Axoneme is the central core of a cilium or flagellum consisting of a central pair of filaments surrounded by nine other pairs.

Equatorial plate is the plane located midway between the poles of a dividing cell during the metaphase stage of mitosis or meiosis. It is formed from the migration of the chromosome to the centre of the spindle.

A.

Meiocyte

In diploid organisms, specialised cells called meiocytes or gamete mother cell undergo meiosis. Conidia and gemmules are asexual reproductive structures found in Penicillium and sponge respectively. Megaspores are female gametes in plants, which undergo sexual reproduction.

A.

Telophase - Nuclear envelope reforms, Golgi complex reforms

Telophase is the phase in which chromosomes are no longer seen and each set of chromatin material tends to collect at each of the two poles.

 Late anaphase is characterised by centromeres split and chrorratid separate and chromatid move to opposite poles.

Cytokinesis is process in which cell itself is divided two daughter cells.