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29/08/2025
Important Vitamins and their chemical names
29/08/2025

Important Vitamins and their chemical names

Important  information for your exams
29/08/2025

Important information for your exams

Important facts to remember for exams
23/07/2025

Important facts to remember for exams

** IMPORTANT years in NCERT Biology **  Helpful for NEET and CUET exam1731 - Many people of Bishnoi community sacrifice ...
02/06/2025

** IMPORTANT years in NCERT Biology **
Helpful for NEET and CUET exam

1731 - Many people of Bishnoi community sacrifice their lives saving trees (Jodhpur)

1770 - Priestley's experiment by Bell Jar, Mice & Mint plant, Candle.

1774 - Discovery of oxygen by Joseph Priestley

1838 - Matthias Schleiden-Cell Theory

1829 - Theodore Schwann- Cell Theory

1850s - Before industrialization => more white wing Moth

1854 - Julius von Sachs proved that glucose is formed in photosynthesis & stored as starch.

1855 - "Omnis cellula cellula" by Rudolf Virchow & complete the cell theory.

1856 - 1863 Mendel work on garden pea.

1860 - Hydroponics technique developed by Julie Von Sache

1865 - Mendel publishes his workon inheritance of character

1866 - Down's Syndrome discovered by Langdon Down.

1869 - DNA as a acidic substance was 1st identified by Friedrich Meischer & termed a "Nuclein"

1891 - Fossils of Java man discovered in Java
- Henking discovered X-body (X-chromosome) in insect. (XO- type s*x determination)

1892 - Discovery of TMV by D.J. Ivanowsky

1898 - M.W. Beijerinck demonstrated infectious nature of TMV
- Discovery of Golgi Body by Camillo Golgi.

1900 - Rediscovery of Mendel's work by ---> • Hugo de Vries
• Karl Corrence
• Tschemark

1902 - Chromosomal theory of inheritance given by Sutton & Bovery.

1905 - Law of limiting factors for plants given by Blackmann

1920 - After Industrialisation => more black moth

1928 - Frederick Griffith's Transformation experiment on Streptococcus pneumonia bacteria

1933 – 1944 - Avery, Macleod McCarty used transformation principle of Griffith's experiment & concluded that DNA is genetic material.

1938 - Coelacanth/Lobe Fines caught in South Africa ---> Ancestor of amphibia.

1947 - At the time of our independence India's population, was approximately 350 million .

1950 - Electron microscope invention
- Tissue culture started

1951 - Family planning was initiated

1952 - Hershey & Chase experiment more correctly proved that DNA ie genetic material [ unquivocal_proof ]

1953 - Discovery of ribosome by George Palade.
- S.L Miller Experiment of evolution.
- Double helical structure model of DNA given by Watson & Crick.

1958 - Matthew Meselson of Franklin Stahl experiment (E. coli in NH4CI medium) proved that DNA replication is semiconservative )
- Taylor study on vicia faba plant (used radioactive thymidind and proved semiconservative nature of DNA)

1960 - Green Revolution.

1963 - Restriction endonuclease isolated from E. coli.

1963 - Wheat varieties Sonalika f Kalyan Sona (High yield & Disease resistant ) introduced in INDIA

1966 - Derived semi dwarf varieties of rice introduced in India.

1969 - R.H. Whittaker proposed FIVE-KINGDOM Classification

1971 - Discovery of viroids by T.O. Diener
- Govt. of India legalised MTP.

1972 - Fluid Mosaic model of plasma membrane by Singer & Nicolson
- 1st recombinant DNA developed by Stanley Cohen and Herbert Boyer
- National committee for environmental planning and Coordination was established.
- Wild life protection act in India.

1974 - Water Act. & also Chipko movement

1980 - Joint Forest movement

1981 - Air act.
- AIDS was fired reported
- Intrinsic growth rate of India (r= 0.0205)

1983 - Eli Lilly American company human Insulin from E. coli.

1984 - Bhopal Tragedy
- Ministry of Environment amd Forest.

1986 - Environment Act (NEPA)

1987 - Noise included in air pollution
- Montreal protocol (Canada)

1988 - National Forest Policy

1989 - Montreal Protocol became effective.

1990 - Delhi ranked 4th among 41 most polluted cities.

1990 - First clinical gene therapy was given to 14 yr old girl with ADA deficiency eye.
- Human Genome Project (HGP) launched.

28/04/2025

IMPORTANT years in ncert :-

1731 - Many people of Bishnoi community sacrifice their lives saving trees (Jodhpur)

1770 - Priestley's experiment by Bell Jar, Mice & Mint plant, Candle.

1774 - Discovery of oxygen by Joseph Priestley

1838 - Matthias Schleiden-Cell Theory

1829 - Theodore Schwann- Cell Theory

1850s - Before industrialization => more white wing Moth

1854 - Julius von Sachs proved that glucose is formed in photosynthesis & stored as starch.

1855 - "Omnis cellula cellula" by Rudolf Virchow & complete the cell theory.

1856 - 1863 Mendel work on garden pea.

1860 - Hydroponics technique developed by Julie Von Sache

1865 - Mendel publishes his workon inheritance of character

1866 - Down's Syndrome discovered by Langdon Down.

1869 - DNA as a acidic substance was 1st identified by Friedrich Meischer & termed a "Nuclein"

1891 - Fossils of Java man discovered in Java
- Henking discovered X-body (X-chromosome) in insect. (XO- type s*x determination)

1892 - Discovery of TMV by D.J. Ivanowsky

1898 - M.W. Beijerinck demonstrated infectious nature of TMV
- Discovery of Golgi Body by Camillo Golgi.

1900 - Rediscovery of Mendel's work by ---> • Hugo de Vries
• Karl Corrence
• Tschemark

1902 - Chromosomal theory of inheritance given by Sutton & Bovery.

1905 - Law of limiting factors for plants given by Blackmann

1920 - After Industrialisation => more black moth

1928 - Frederick Griffith's Transformation experiment on Streptococcus pneumonia bacteria

1933 – 1944 - Avery, Macleod McCarty used transformation principle of Griffith's experiment & concluded that DNA is genetic material.

1938 - Coelacanth/Lobe Fines caught in South Africa ---> Ancestor of amphibia.

1947 - At the time of our independence India's population, was approximately 350 million .

1950 - Electron microscope invention
- Tissue culture started

1951 - Family planning was initiated

1952 - Hershey & Chase experiment more correctly proved that DNA ie genetic material [ unquivocal_proof ]

1953 - Discovery of ribosome by George Palade.
- S.L Miller Experiment of evolution.
- Double helical structure model of DNA given by Watson & Crick.

1958 - Matthew Meselson of Franklin Stahl experiment (E. coli in NH4CI medium) proved that DNA replication is semiconservative )
- Taylor study on vicia faba plant (used radioactive thymidind and proved semiconservative nature of DNA)

1960 - Green Revolution.

1963 - Restriction endonuclease isolated from E. coli.

1963 - Wheat varieties Sonalika f Kalyan Sona (High yield & Disease resistant ) introduced in INDIA

1966 - Derived semi dwarf varieties of rice introduced in India.

1969 - R.H. Whittaker proposed FIVE-KINGDOM Classification

1971 - Discovery of viroids by T.O. Diener
- Govt. of India legalised MTP.

1972 - Fluid Mosaic model of plasma membrane by Singer & Nicolson
- 1st recombinant DNA developed by Stanley Cohen and Herbert Boyer
- National committee for environmental planning and Coordination was established.
- Wild life protection act in India.

1974 - Water Act. & also Chipko movement

1980 - Joint Forest movement

1981 - Air act.
- AIDS was fired reported
- Intrinsic growth rate of India (r= 0.0205)

1983 - Eli Lilly American company human Insulin from E. coli.

1984 - Bhopal Tragedy
- Ministry of Environment amd Forest.

1986 - Environment Act (NEPA)

1987 - Noise included in air pollution
- Montreal protocol (Canada)

1988 - National Forest Policy

1989 - Montreal Protocol became effective.

1990 - Delhi ranked 4th among 41 most polluted cities.

1990 - First clinical gene therapy was given to 14 yr old girl with ADA deficiency eye.
- Human Genome Project (HGP) launched.

What types of ecosystems may exist here?
05/02/2025

What types of ecosystems may exist here?

Why blood is called a non-newtonian fluid?
11/12/2024

Why blood is called a non-newtonian fluid?

08/08/2024

BR BIOLOGY CLASS

CLASS XI
Cell Cycle and Cell Division NEET Questions
1. Which of the following is the longest phase of the cell cycle?
(1) Prophase
(2) Interphase
(3) Telophase
(4) M – phase


2. The first gap phase in the cell cycle is________
(1) interval between mitotic phase and DNA replication phase
(2) interval between the DNA replication phase and DNA separation phase
(3) interval between karyokinesis and cytokinesis
(4) interval between the DNA replication phase and the second gap phase


3. Interphase includes in_______
(1) G0, G1, S, G2
(2) Prophase, Metaphase, Anaphase, Telophase
(3) Cytokinesis
(4) Mitosis / M-phase


4. The two chromatids of a metaphase chromosome represent_______
(1) Replicated DNA to be separated at anaphase
(2) nonhomologous chromosomes joined at the centromere
(3) Pair of homologous chromosomes
(4) maternal and paternal chromosomes joined at the centromere


5. The stage during which separation of the paired homologous chromosomes begins is_________
(1) Pachytene
(2) Diplotene
(3) Diakinesis
(4) Zygotene


6. If you are provided with the root tips of an onion in your class and are asked to count the chromosomes which of the following stages can you most conveniently look into:
(1) Prophase
(2) Anaphase
(3) Telophase
(4) Metaphase


7. In mitosis, the nuclear envelope and nucleolus disappear during________
(1) Metaphase
(2) Interphase
(3) Prophase
(4) Telophase


8. This condition is necessary for a cell to qualify through the G2 checkpoint_________
(1) Cell should be of sufficient size
(2) Complete and accurate DNA replication
(3) Sufficient stockpile of nucleotides
(4) Complete attachment of mitotic spindle fibers to kinetochores


9. Individual chromosomes become distinct through a light microscope during this mitotic stage_________
(1) Prometaphase
(2) Prophase
(3) Anaphase
(4) Metaphase


10. Chromosome duplication without nuclear division refers to_______
(1) mitosis
(2) endomitosis
(3) meiosis
(4) androgenesis


11. Recombination of genes occur at____________
(1) prophase I in meiosis
(2) prophase II in meiosis
(3) metaphase II in meiosis
(4) Prophase in mitosis


12. The stage between two meiotic divisions is called interkinesis and__________
(1) Is generally short-lived and followed by prophase II
(2) Involves duplication of genes and centrioles
(3) Is followed by prophase I.
(4) Is long-lived


13. A cell that is entering the mitotic phase (M-phase) of the cell cycle is______
(1) always haploid and with duplicated chromosomes
(2) either haploid or diploid and with duplicated chromosomes
(3) either haploid or diploid and with duplicated or unduplicated chromosomes
(4) always diploid and with unduplicated chromosomes

14. Synaptonemal complex is a nucleoprotein structure. It is visible or found from________
(1) zygotene to pachytene
(2) leptotene to diplotene
(3) zygotene to metaphase
(4) Pachytene to diplotene

15. Which one of the following is correctly matched?
(1) Leptotene – formation of bivalents
(2) Diplotene – chiasmata appear
(3) Pachytene – chiasmata formation
(4) Zygotene – formation of bouquet


16. In which stage of meiosis, chromosomes are thin, long, or thread-like?
(1) Zygotene
(2) Leptotene
(3) Pachytene
(4) Diakinesis


17. Meiosis involves in_________
(1) one nuclear division and one chromosome division
(2) two nuclear divisions and one chromosome division
(3) one nuclear division and two chromosome divisions
(4) Two nuclear divisions and two chromosome divisions


18. In meiosis, centromeres of chromosomes divide during_________
(1) anaphase of meiosis-II
(2) metaphase of meiosis-I
(3) anaphase of meiosis-I
(4) Prophase of meiosis-II


19. A cell examined during the prophase of the cell cycle contained 100 units of DNA and 50 chromosomes. What would be the number of DNA and chromosomes in the anaphase of this cell cycle?
(1) 200 DNA & 100 chromosomes
(2) 100 DNA & 50 chromosomes
(3) 100 DNA & 100 chromosomes
(4) 50 DNA & 25 chromosomes


20. During the cell cycle in which phase normal components of the cell are synthesized, and assembled?
(1) S
(2) G2
(3) G1
(4) M


21. Spindle fibers attach on to_________
(1) Telomere of the chromosome
(2) Kinetochore of the chromosome
(3) Centromere of the chromosome
(4) Kinetosome of the chromosome


22. Which type of chromosome is present in the prophase of the cell cycle?
(1) 2 chromatid
(2) 1 chromatid
(3) 4 chromatid
(4) 8 chromatid


23. A somatic cell that has just completed the S phase of its cell cycle, as compared to a gamete of the same species, has_________
(1) Same number of chromosomes but twice the amount of DNA
(2) twice the number of chromosomes and four times the amount of DNA
(3) four times the number of chromosomes and twice the amount of DNA
(4) twice the number of chromosomes and twice the amount of DNA


24. Arrange the following events of meiosis in the correct sequence_________
(a) Crossing over
(b) Synapsis
(c) Terminalization of charismata
(d) Disappearance of nucleolus
(1) (b), (c), (d), (a)
(2) (b), (a), (d), (c)
(3) (b), (a), (c), (d)
(4) (a), (b), (c), (d)


25. Which of the following options gives the correct sequence of events during mitosis?
(1) Condensation -> nuclear membrane disassembly -> arrangement at equator -> centromere division -> segregation -> telophase
(2) Condensation -> crossing over -> nuclear membrane disassembly -> segregation -> telophase
(3) Condensation -> arrangement at equator -> centromere division -> segregation -> telophase
(4) Condensation -> nuclear membrane disassembly -> crossing over -> segregation -> telophase


26. Anaphase Promoting Complex (APC) is a protein degradation machinery necessary for the proper mitosis of animal cells. If APC is defective in a human cell, which of the following is expected to occur?
(1) Chromosomes will be fragmented
(2) Chromosomes will not segregate
(3) Recombination of chromosome arms will occur
(4) Chromosomes will not condense


27. In meiosis crossing over is initiated at:
(1) Pachytene
(2) Leptotene
(3) Zygotene
(4) Diplotene


28. During cell growth, DNA synthesis takes place in________
(1) G2 phase
(2) M phase
(3) S phase
(4) G1 phase

29. When a cell has stalled DNA replication fork, which checkpoint should be predominantly activated?
(1) M
(2) Both G2 / M and M
(3) G1 / S
(4) G2 / M


30. The complex formed by a pair of synapsed homologous chromosomes is called________
(1) Axoneme
(2) Equatorial plate
(3) Kinetochore
(4) Bivalent


31. On which phase of the cell cycle does the amount of DNA in a diploid cell become four times as compared to a haploid cell?
(1) G1
(2) S
(3) G2, S & s
(4) Go


32. During which phase (s) of the cell cycle does, the amount of DNA in a cell remains at 4C level if the initial amount is denoted as 2C?
(1) G0 and G1
(2) G1 and S
(3) Only G2
(4) G2 and s


33. On the ‘S’ phase of the cell cycle_____
(1) The amount of DNA doubles in each cell.
(2) The amount of DNA remains the same in each cell.
(3) Chromosome number is increased.
(4) The amount of DNA is reduced to half in each cell.


34. The enzyme recombinase is required at which stage of meiosis__________
(1) Pachytene
(2) Zygotene
(3) Diplotene
(4) Diakinesis


35. Identify the meiotic stage in which the homologous chromosomes separate while the sister chromatids remain associated at their centromeres_______
(1) Anaphase I.
(2) Anaphase II
(3) Metaphase I.
(4) Metaphase II


36. Which of the following is wrong about the G1 phase?
(1) G-1 Stage followed by Mitosis
(2) Cell is metabolically active
(3) Cell grows continuously
(4) Cell does not replicate its DNA


37. Select the correct option concerning mitosis_________
(1) Chromatids separate but remain in the center of the cell in anaphase.
(2) Chromatids start moving towards opposite poles in telophase.
(3) Golgi complex and endoplasmic reticulum are still visible at the end of prophase.
(4) Chromosomes move to the spindle equator and get aligned along the equatorial plate in metaphase

38. At metaphase, chromosomes are attached to the spindle fibers by their_________
(1) Centromere
(2) Satellites
(3) Secondary constrictions
(4) Kinetochores


39. Meiosis is not having one of the characters out of the four given below________
(1) It involves two stages of DNA replication, “one before meiosis-I and another before meiosis-II
(2) It involves recombination and crossing over
(3) Sister chromatids separate during anaphase-II
(4) Nuclear membrane disappears during prophase


40. During gamete formation, the enzyme recombinase participates during_______
(1) Prophase-I
(2) Prophase-II
(3) Metaphase-I
(4) Anaphase-II


41. A cell has 46 chromosomes at each pole in mitotic telophase. on this division, the number of chromatids at the metaphase was_________
(1) 23
(2) 46
(3) 92
(4) 69


42. A mouse cell is treated with a chemical that interferes with the activity of microfilaments. Which of the following will probably be affected the most?
(1) Formation of spindle fibers
(2) Division of cytoplasm
(3) Chromosome duplication
(4) Pairing of homologous chromosomes


43. Number of chromosome pairs at the equator in metaphase-o of a diploid plant cell (n = 25) chromosomes) shall be__________
(1) 50
(2) 100
(3) 75
(4) 25


44. How many meiotic divisions are required during the formation of 500 zygotes, if in males one meiotic division results in the formation of four male gametes and in females one meiotic division results in the formation of one female gamete?
(1) 625
(2) 500
(3) 1000
(4) 2500


45. The number of chromatids in each chromosome at anaphase is__________
(1) One in mitosis, one in meiosis-I, and two in meiosis-I
(2) One in mitosis, two in meiosis-I and one in meiosis-II
(3) Two in mitosis, one in meiosis-I and two in meiosis-II
(4) Two in mitosis, two in meiosis-I and two in meiosis-II


46. Which of the following is not correctly match a phase of the cell cycle with its function?
(1) Second gap phase – Period of cytoplasmic
growth
(2) First gap phase – the cost of the organelle duplication
(3) Interphase – Phase of preparation
for cell division
(4) DNA synthesis – Doubling of number of phases
chromosome in cell


47. Mark incorrect statements_________
(A) Neiosis involves only a single cycle of DNA replication
(B) Four haploid cells are formed at the end of meiosis – I
(C) Meiosis occurs in diploid cells
(D) On yeast, the cell cycle takes about 90 minutes.
(1) A and B
(2) A and C
(3) Only B
(4) All are correct


48. Meiosis involves in_________
(1) Pairing of homologous chromosomes and recombination between sister chromatids of nonhomologous chromosomes
(2) Pairing of homologous chromosomes and recombination between non-sister chromatids of homologous chromosomes
(3) Pairing of nonhomologous chromosomes and recombination between non-sister chromatids of homologous chromosomes
(4) Pairing of homologous chromosomes and recombination between sister chromatids of homologous chromosomes

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