Cell Cycle And Cell Division Class 11 :- Growth and reproduction are the characteristic feature of any living organisms.Both are dependent on cell division.Cell division allows a single organisms to perform so many works.With the help of cell division one parental cell divides into two daughters cell to give rise a new organism. Cell division occur in a cyclic way that is known as a cell cycle.The cell cycle is divided into different phases such as Interphase,S phase ,G1&G2phase.
Cell Cycle And Cell Division Class 11 – Very Short Answer Type Questions
Q.1. Write the name of the cell between a eukaryote and a prokaryote that has a shorter cell division time?
A.1. Compared to a eukaryotic cell a prokaryotic cell has a shorter cell cycle.
Q.2. Write the name of the cell cycle phase that has the longest duration?
A.2. The interphase has the longest duration.
Q.3. Write the name of stain which is usually used to colour chromosomes?
A.3. Giemsa and Acetocarmine is used usually to colour chromosomes.
Q.4. Write the name of the plant and animal tissue that undergoes meiosis.
A.4. Meiosis occurs in the germ cells of female and male reproductive organs in animals and plants, that produces female and male gametes which participate in sexual reproduction.
Q.5. In 20 minutes how much time will two E. Coli cells take to become 32 cells if the average duplication time of E. coil ?
A.5. E.coli takes 1 hour and 20 minutes.There are four succeeding cell divisions which generate 16 cells where each division takes a total of 20 minutes. Hence, the total time = 20 x 4 = 80 minutes or 1 hour and 20 minutes. Thus, 1 cell produces 16 cells in 80 minutes and 2 cells produce 32 cells in 1 hour and 20 minutes.
Q.6. Write the name of a human body part which can be utilized to illustrate mitosis phases?
A.6.Somatic cell of the human body part can be utilised to illustrate mitosis phases .
Cell Cycle And Cell Division Class 11 Quiz
Q.7. What attributes are needed for a chromatid to be classified as a chromosome?
A.7.Crossing over attributes.
Q.8. In which phase of the cell cycle does the DNA get synthesized?
A.8. In the S-phase or Synthetic phase of the interphase the DNA get synthesized.
Q.9. Write the name of the longest phase in the cell cycle.
A.9. Interphase is the longest phase of the cell cycle.
Q.10.To colour chromosomes which stains are used?
A.10. Gentian violet, Giemsa stain and Safranin are commonly used to colour chromosomes.
Cell Cycle And Cell Division Class 11 – Short Answer Type Questions
Q.1. Write the role of centrioles apart from spindle formation.
A.1. In a centrosome, two centrioles are arranged perpendicular to each other and organized in a cartwheel pattern. In animal cell division, it form the basal body of cilia and flagella of animal/plant cells. It also assists in the formation of sperms tail and the microtubules.
Q.2. During nuclear divisions such as mitosis what happens to the DNA of the plastids and the mitochondria is?
A.2.The Chloroplasts and mitochondria bears DNA in the form of extrachromosomal DNA and have no any role in nuclear division. In mitosis only nuclear DNA takes place.
Q.3. One cell has 32 chromosomes which undergo mitotic division. What will be the chromosome number (N) of the cell during metaphase? And What will the DNA content of the cell be during Anaphase?
A.3. Mitosis occurs in the somatic cells of the living organisms. The number of chromosomes is same in both the parents and daughter cells and they remain unchanged even at anaphase or metaphors. The DNA content however, is doubled at the interphase or the synthetic phase. The cell division takes place at the anaphase but the chromosome number remains unchanged.
Q.4 Which tissue of animals and plants that exhibit meiosis?
A.4. Meiosis takes place only in gametic cells or tissue. In animals, reproductive cells or germ cells the meiosis occur and it includes the testes and ovaries cell. In plants, in the Androecium (male reproductive) and Gynoecium (female reproductive) parts the Meiosis occurs.
the meiosis occurs Q.5. What is the pathological condition which occurs under uncontrolled cell division?
A.5. . In Cancerous condition, the cells lose the control of cell division and undergo uncontrolled cell division.
Q.6. In the diplotene phase for months and year which cell is captured ? How does they complete their cell cycle?
A.6. In the oocytes of a few vertebrates diplotene can last for months or years.
- In diplotene phase of few animal oocytes of amphibians or frogs diplotene chromosome present.
- In meiotic prophase, lampbrush chromosomes are observed. Lampbrush chromosomes tend to turn normal after the growth, thereby they completes their cell cycle.
Cell Cycle And Cell Division Class 11 – Long Answer Type Questions
Q.1. Justify the statement.Telophase is the reverse of prophase.
A.1. Prophase is initiated by the condensation of chromosomal material. Chromosomal material untangles during process of chromatin condensation. During t starting of the final stage of mitosis, i.e.,telophase, upon arrival at their own respective poles, chromosomes de-condenses and losses their individuality. When it is observed under a microscope, cells at end of prophase disappear Golgi complexes, nucleolus, endoplasmic reticulum, and nuclear envelope. Nuclear envelope at telephone stage gathers around cluster of the chromosomes. And the Golgi complex, ER, nucleolus reappear.
Q.2. Explain the different phases of meiotic prophase – I.Give the chromosomal events during each stage.
A.2. During prophase – I, genetic recombination and variation in sexually reproducing living organisms takes place due to events of this stage.
Leptotene
- Chromosomes are very long, thin and cylindrical
- Chromatin networks exposes and the threads appear very clearly
- Diploid number of chromosomes are present
Zygotene
- The similar chromosomes become intimately associated
- The Synapse is exact therefore pairing is not just between chromosomes, but between corresponding individual units.
- The chromosomes appears very thicker and shorter
Pachynema
- Synaptic chromosomes become closely related
- Chromosomes having thick and short
- Crossing over occurs, the Chiasmata is clearly visible
Diplotene
- The homologous chromosomes starts detaching from each other.
- The chiasmata tends to shift away from the chromosomes, termed as terminalization of chiasmata.
- The chromosomes detached out, but this is an incomplete separation
- Nucleolus and the nuclear membrane start to fade.
Diakinesis
- The bivalents distributed randomly after further condensation
- The paired chromosomes separate completely
- Terminalisation of chiasmata is almost concluded
- The disappearance of the nuclear membrane and the nucleolus.
Cell Cycle And Cell Division Class 11 Topeers notes
Q.3. Write the differences between events of meiosis and mitosis.
A.3. Following are the differences between mitosis and meiosis
| Attributes | Mitosis | Meiosis |
| The place of occurrence | In the somatic cells | In the Germ cells |
| Nature of an Organisms | Both Asexually and sexually reproducing organisms | Only Sexually reproducing organisms |
| The nuclear and cell division | One cycle in each | Their are Two sequential cycles – Meiosis I & II |
| The DNA replication | each cell division for once | for two cell divisions once |
| Duration of the prophase | Short duration | Long duration |
| Nature of the prophase | Simple nature | first meiotic division is in comparison to prophase of mitosis |
| Cell division and chromosome division | Both cell division and chromosome division divide once each | There are Two cell divisions, but one chromosome division |
| End product | Two cells | Four haploid cells |
Q.4. Give a brief description on:
a) Synaptonemal complex
b) Metaphase plate
A.4. a) They are zipped-structures which assemble during the prophase of the meiosis – I in between homologous chromosomes. The disassembly and assembly is interlinked with continuous rearrangements of chromatin during meiotic prophase in such a manner the poring, recombination, condensation, and dysfunction of homologous chromosomes. They regulate number and distribution of reciprocal exchanges between homologous chromosomes. After that they convert the cross over to functional chiasmata.
b) Centromeres of chromosomes in metaphase gather on the metaphasic plate which is an imaginary line at an equal distance from the two centrosome poles. The alignment is due to opposite kinetochore microtubules. The chromosomes at this plate, sister chromatids, in particular, are joined to the package of four to eight spindle fibres.
Q.5. Write the name of phases of the cell cycle against each of the events
a) Disintegration of nuclear membrane
b) Appearance of nucleolus
c) Division of the centromere
d) Replication of the DNA
A.5. a)The Prophase.
b) The Telophase.
c) The Anaphase.
d)The S-phase.
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