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Class 11 Biology textbook Solutions for Class 11, Biology Chapter 7 Cell Division maharashtra state board are provided here with simple step-by-step detailed explanations. These solutions for Cell Division are very popular among Class 11 students for biology chapter 7 Cell Division Solutions come handy for quickly completing your homework and preparing for compititive exams like NEET, CET abd verious medical entrance examination also. All questions and answers are taken from the class 11 Biology textbook, Bjology Textbook Solutions of Class 11 Biology Chapter 7 are provided here for you for without any charge its free for you. All Biology textbook Solutions for class 11. Solutions for class 11 Biology subject, These biology textbook solutions are prepared by experts in the field and are 100% accurate for you.
1. Choose correct option
A. The connecting link between Meiosis-I
and Meiosis-II is ……………
B. Synapsis is pairing of ………….
a. any two chromosomes
b. non-homologous chromosomes
c. sister chromatids
d. homologous chromosomes
C. Spindle apparatus is formed during which stage of mitosis?
D. Chromosome number of a cell is almost doubled up during ……………
E. How many meiotic divisions are necessary for formation of 80 sperms?
F. How many chromatides are present in anaphase-I of meiosis-I of a diploid cell having 20 chromosomes?
G. In which of the following phase of mitosis chromosomes are arranged at equatorial plane?
H. Find incorrect statement –
a. Condensation of chromatin material
occurs in prophase.
b. Daughter chromatids are formed in anaphase.
c. Daughter nuclei are formed at metaphase.
d. Nuclear membrane reappears in telophase.
I. Histone proteins are synthesized during ……
a. G1 phase
2. Answer the following questions
A. While observing a slide, student observed many cells with nuclei. But some of the nuclei were bigger as compared to others but their nuclear membrane was not so clear. Teacher inferred it as one of the
phase in the cell division. Which phase may be inferred by teacher?
Answer : The phase which was inferred by the teacher was ‘Prophase’. Because In this phase, the chromosomes starts getting condensed. If this phase occurs in cells of animal then the centrioles starts moving in the opposite ends or poles. Mitotic Spindle starts appearing in this phase.
B. Students prepared a slide of onion root tip. There were many cells seen under microscope. There was a cell with two groups of chromosomes at opposite ends of the cell. This cell is in which phase of mitosis?
Answer : The Anaphase is the mitosis phase revealing two groups of chromosomes at opposite ends of the cell. because of The most commonly used is the root tip to study the mitosis reaction. The onion tip is squashed which allows being flattened on the microscope.
The DNA specific stains are used to view the DNA under the microscope are Fuelgen stains and acetocarmine stain.
C. Students were shown some slides of cancerous cells. Teacher made a comment as if there would have been
a control at one of its cell cycle phase, there wouldn’t have been a condition like this. Which phase the teacher was
Answer : This phase was the initial phase, phase I. The phase I can be treated with chemotherapy but cannot be controlled or by any medicinal treatment. Cancer cannot be completely cured but it can be treated, in the initial stage but at the last stage, the treatment is very difficult.
D. Some Mendelian crossing experimental results were shown to the students. Teacher informed that there are two genes located on the same chromosome. He enquired if they will be ever separated from each other?
Answer : When two genes are located on the same chromosome and as much they are near to each other they defy the Mendel’s Law of Independent Assortment which says that “alleles coding for separate traits are passed independently of one another” but William Bateson, Edith Rebecca Saunders and Reginald Punnett in 1905 discovered the phenomenon of Genetic linkage, according to which two genes located on the same chromosome and are near to each other are unlikely to get separated and tends to gets inherited together. So, there is a very low probability of the two genes to separate from each other. However, the most important consideration in this matter will be the distance between them.
E. Students were observing a film on
Paramoecium. It underwent a process
of reproduction. Teacher said it is due to cell division. But students objected and said that there was no disappearnce of nuclear membrane and no spindle formation, how can it be cell division? Can you clarify?
Answer : reproduction in paramecium is through binary fission
Explanation: During reproduction, the macronucleus splits by a type of amitosis, and the micronuclei undergo mitosis. The cell then divides transversally, and each new cell obtains a copy of the micronucleus and the macronucleus.
F. Is the meiosis responsible for evolution? Justify your answer
Answer : Yes, Meiosis is responsible for evolution. Explanation: During Meiosis, recombination occurs which leads to variation in the progeny. So, variations due to Meiosis are considerable factors for evolution
G. Why mitosis and meiosis-II are called
as homotypic division?
Answer: Mitosis and Meiosis 2 is called equational or homotypic division because number of chromosomes remain equal before and after division.
H. Write the significance of mitosis.
- Mitosis results in the production of diploid daughter cells with identical genetic complement usually.
- Cell divides by mitosis to restore the nucleo-cytoplasmic ratio.
- Helps in cell repair. Mitotic divisions in the meristematic tissues result in a continuous growth of plants throughout their life.
I. Enlist the different stages of prophase-I.
Answer : Prophase I. Prophase I is divided into five phases: leptotene, zygotene, pachytene, diplotene, and diakinesis.
3. Draw labelled digrams and write explanation
A. With the help of suitable diagram,
describe the cell cycle.
Answer : Sequential events occurring in the life of a cell is called cell cycle. There are two phases of cell cycle as interphase and M-phase. During interphase, cell undergoes growth or rest as per the need. During M-phase, the cell undergoes division. Interphase alternates with the period of division.
Interphase : Interphase is the stage between two successive cell divisions. It is the longest phase of cell cycle during which the cell is highly active and prepares itself for cell division. The interphase is divisible into three sub-phases as G1-phase, S-phase and G2-phase.
G1-phase : This is also known as first gap period or first growth period. It starts immediately after cell division. Cell performs RNA synthesis (mRNA, rRNA and t-RNA), protein synthesis and synthesis of membranes during this phase.
S-phase : It is synthesis phase in which DNA is synthesized or replicated, so that amount of DNA per cell doubles. Histone proteins are also synthesized during this phase.
G2 phase : G2 is the second growth phase,
during which nucleus increases in volume.
Metabolic activities essential for cell division occur during this phase. Various proteins necessary for cell division are synthesized during this phase. Besides, RNA synthesis also occur during this phase. In animal cells, a daughter pair of centrioles appear near the pre-existing pair.
M-phase or period of division : ‘M’ stands
for mitosis or meiosis. M-phase involves
karyokinesis and cytokinesis. Karyokinesis is the division of nucleus into two daughter nuclei whereas cytokinesis is division of cytoplasm resulting in two daughter cells
B. Distinguish between mitosis and meiosis.
1) mitosis division takes place in somatic cells and as a result of this division growth occurs. Meisis takes place usually in reproductive cells and as a result of this character one generation pass into the other.
2) Mitosis Completed in one stage. Meiosis Completed in two stages.
3) Mitosis. Prophase is smaller (as compared to prophase of Meiosis). Meiosis Prophase longer than prophase of mitosis and divided into five substages.
4) In mitosis No crossing over takes place. In Meiosis Crossing over takes place in which exchange of segments of chromatids occurs.
5) Synapsis does not take place at metaphase. In Meiosis Synapsis between homologous chromosomes takes place (bivalent stage).
6) At metaphase, centromere is towards equatorial plate and ends of chromosomes towards poles. Centromere divides. In Meiosis metaphase I, the centromere is towards poles and ends of chromosomes towards equatorial plate. Centromere does not divide.
7) Chromatids are long and thin. In Meiosis Chromatids are shorter and thick
8) In mitosis Cytokinesis follows karyokinesis. In Meiosis Telophase I, cytokinesis does not takes place always (may occur).
C. Draw the diagram of metaphase.
4. Match the following column-A with column B
Column-A(phases) Column-B(Their events)
a. Leptotene.. 1. Crossing over
b. Zygotene. 2. Desynapsis
c. Pachytene. 3. Synapsis
d. Diplotene. 4. Bouquet stage
a. Leptotene →Bouquet stage
b. Zygotene →Synapsis
c. Pachytene →Crossing Over
6. If an onion has 16 chromosomes in its leaf cell, how many chromosomes will be there in its root cell and pollen grain.
Answer : pollen grains in the somatic cells remains the same.show the leaf cell in the root cell of the onion are the somatic cells.the number of chromosomes here for both somatic cells of onion will be 16 chromosomes only.