Solution: This phase shows the Late prophase stage of cell division, where spindle fibers have become prominent and the chromosomes are arranging themselves towards the equator for the next phase.
An organism has two pair of chromosomes (i.e., chromosome number = 4). Diagrammatically represent the chromosomal arrangement during different phases of meiosis-II.
Solution: Cell division and cell cycle are two separate processes that occur in your body. Cell division is the process of two daughter cells multiplying from a single parent cell. Eukaryotic cells...
Write briefly the significance of mitosis and meiosis in a multicellular organism.
Solution: Mitosis and Its Importance: Mitosis helps a single-cell zygote develop into a fully formed creature. It aids an organism's development.It aids in the healing of worn or injured tissues.It...
Write a brief note on the following
a. Synaptonemal complex
b. Metaphase plate
Solution: Following is the description of each of the given topics- a. Synaptonemal complex- It is made up of protein that is generated when two homologous chromosomes come together. The complex...
Differentiate between the events of mitosis and meiosis.
Solution: The difference between Mitosis and Meiosis are- MitosisMeiosis1. The prophase will be brief.1. Prophase I lasts a long time while prophase II lasts a short time.2. During metaphase, just...
What are the various stages of meiotic prophase-I? Enumerate the chromosomal events during each stage?
Solution: Prophase I –LeptoteneThe nuclear membrane begins to dissolve at the leptotene stage.The chromatin material begins to condense.Centriole reaches the poles in opposite...
Comment on the statement – Telophase is reverse of prophase.
Solution: Chromosomes condense during prophase. The nuclear membrane breaks down. Organelles such as mitochondria, the endoplasmic reticulum, and the Golgi apparatus vanish. Golgi complexes,...
Name a cell that is found arrested in diplotene stage for months and years. Comment in 2-3 lines how it completes the cell cycle?
Solution: In the diplotene stage, the oocyte of mammalian females are arrested. The oocyte develops into a secondary follicle before being stopped at the diplotene stage. The first meiosis is...
Comment on the statement – Meiosis enables the conservation of specific chromosome number of each species even though the process per se, results in a reduction of chromosome number.
Solution: When two haploid cells called gametes combine during fertilization, a diploid zygote is created. In the absence of meiosis, two diploid gametes are generated, resulting in the creation of...
10. Two key events take place, during S phase in animal cells, DNA replication and duplication of the centriole. In which parts of the cell do events occur?
Solution: During the S phase in animal cells the process of centriole duplication takes place in the cytoplasm, while DNA replication takes place in the nucleus.
Name the pathological condition when uncontrolled cell division occurs.
Solution: Tumor or cancer is a pathological condition caused by uncontrolled cell division and abnormal cell development. This is called malignancy caused due to cancer.
Both unicellular and multicellular organisms undergo mitosis. What are the differences, if any, observed in the process between the two?
Solution: Amitosis occurs in prokaryotes, where the cell divides into two daughter cells. In multicellular creatures, however, normal cell division procedures are followed: first, karyokinesis, then...
7. Mitosis results in producing two cells which are similar to each other. What would be the consequence if each of the following irregularities occur during mitosis?
a. Nuclear membrane fails to disintegrate
b. Duplication of DNA does not occur
c. Centromeres do not divide
d. Cytokinesis does not occur
Solution: (a) The spindle fibers would be unable to reach chromosomes if the nuclear membrane failed to dissolve. As a result, chromosomes would be unable to reach the cell's opposite poles. (b) If...
The following events occur during the various phases of the cell cycle, Name the phase against each of the events.
a. Disintegration of nuclear membrane_________________________
b. Appearance of nucleolus_________________________
c. Division of centromere_________________________
d. Replication of DNA _________________________
Solution: The following are the events and their phases. (a)Disintegration of nuclear membrane - Prophase. (b) Appearance of nucleolus -Telophase. (c) Division of centromere - Anaphase. (d) ...
While examining the mitotic stage in a tissue, one finds some cells with 16 chromosomes and some with 32 chromosomes. What possible reasons could you assign to this difference in chromosome number? Do you think cells with 16 chromosomes could have arisen from cells with 32 chromosomes or vice versa?
Solution: The most possible reason for this phenomenon is mosaicism. Mosaicism refers to the coexistence of two populations of cells with different genotypes in a single person. Mosaicism can occur...
A cell has 32 chromosomes. It undergoes mitotic division. What will be the chromosome number (N) during metaphase? What would be the DNA content (C) during anaphase?
Mitochondria and plastids have their DNA (genetic material). What is known about their fate during nuclear division like mitosis?
Solution: Extrachromosomal DNA is the DNA found in mitochondria and plastids. They are unaffected by nuclear DNA division in the nucleus. As a result, mitosis has no effect on extrachromosomal DNA.
State the role of centrioles other than spindle formation.
Solution: Apart from forming spindles, centrioles also serve as the foundation for cilia and flagella. Microtubules and the sperm tail are also formed with their assistance. Centriole forms the...
In which phase of meiosis is the following formed? Choose the answers from hint points given below.
a. Synaptonemal complex ____________________________
b. Recombination nodules ____________________________
c. Appearance/activation of ____________________________ enzyme recombinase
d. Termination of chiasmata _ ___________________________
e. Interkinesis ____________________________
f. Formation of dyad of cells _ ___________________________
Hints : 1) Zygotene, 2) Pachytene, 3) Pachytene, 4) Diakinesis, 5) After Telophase-I /before Meosis-II, 6) Telophase-I /After Meiosis-I.
Solution: During meiosis, a protein structure called the synaptonemal complex (SC) arises between homologous chromosomes (two pairs of sister chromatids) and is visible in the zygotene stage because...
It is observed that heart cells do not exhibit cell division. Such cells do not divide further and exit ___________ phase to enter an inactive stage called ___________ of cell cycle. Fill in the blanks.
Solution: It has been discovered that cardiac cells do not divide. Such cells do not divide further and exit the G1 phase of the cell cycle, entering the dormant G0 stage. So, the answers are the G1...
It is said that the one cycle of cell division in human cells (eukaryotic cells) takes 24 hours. Which phase of the cycle, do you think occupies the maximum part of the cell cycle?
Solution: Interphase is the phase of the cycle that takes 23 hours out of 24 hours. It's important to note that during a human cell's 24-hour average cell cycle, cell division lasts only...
At what stage of the cell cycle does DNA synthesis take place?
Solution: In this phase, DNA synthesis takes to occur. A cell must make a fresh copy of its chromosomes before it may divide. It takes both the replication of the lengthy DNA molecule in each...
An anther has 1200 pollen grains. How many pollen mother cells must have been there to produce them?
Solution: One Pollen Mother Cell (PMC) produces four haploid pollen grains during meiosis. Thus, 1200/4=300 PMCs are required to produce 1200 pollen grains. 1 pollen mother cell →4 pollen grain....
If the tissue has at a given time 1024 cells, how many cycles of mitosis had the original parental single-cell undergone?
Solution: Each cycle results in the formation of two daughter cells. The formula is (2 ^ number of cycles = number of daughter cells). Therefore, 2x=1024, which implies X=10. So, if we check...
The diagram shows a bivalent at prophase-I of meiosis. Which of the four chromatids can cross over?
Solution: In this situation, non-sister chromatids can cross over. Crossing over always takes place between two non-sister chromatids and never between two sister chromatids. Sister chromatids of...
What attributes does a chromatid require to be classified as a chromosome?
Solution: To be recognized as a chromosome, there must be two identical sister chromatids linked at the centromere's center. So, when chromatids are attached to the centromere it is termed as a...
Which part of the human body should one use to demonstrate stages in mitosis?
Solution: Human skin cells, hair follicles, and intestinal epithelial cells are constantly dividing, and hence stages of mitosis can be detected. So, the tissues near the cheeks can be taken to...
Given that the average duplication time of Escherichia coli is 20 minutes, how much time will two Escherichia coli cells take to become 32 cells?
Solution: To create 32 cells, Escherichia coli cells must go through 5 division cycles, resulting in ${{2}^{5}}=32$ cells. 1→ 2 →4 →8 →16 →32 cells. Each cycle takes 20 minutes to...
Which tissue of animals and plants exhibits meiosis?
Solution: To produce gametes, germ cells in the reproductive tract goes through a process called meiosis. Only the reproductive cells or germ cells (gametes) of the organism undergo meiosis,...
Name a stain commonly used to colour chromosomes.
Solution: The cell is stained with Acetocarmine and mounted in acetocarmine alone and Giemsa to make the chromosomes visible.
Which of the phases of the cell cycle is of longest duration?
Solution: The G1 phase is the longest in the cell cycle. It's the beginning of the interphase. The cell prepares for division during the G1 phase. During the G1 phase, cells are extremely...
Between a prokaryote and a eukaryote, which cell has a shorter cell division time?
Solution: Cell division in prokaryotic cells is faster than in eukaryotic cells. Human cells in culture demonstrate a typical eukaryotic cell cycle. These cells divide once every 24 hours on...
Select the correct statement about G1 phase
a. The cell is metabolically inactive
b. DNA in the cell does not replicate
c. It is not a phase of synthesis of macromolecules
d. Cell stops growing
Solution: G 1 is the metabolically active stage of the cell cycle's interphase. The synthesis of ATP nucleotides, amino acids, RNAs, and proteins takes place during G 1, and the nucleus grows. In...
Identify the wrong statement about meiosis
a. The pairing of homologous chromosomes
b. Four haploid cells are formed
c. At the end of meiosis, the number of chromosomes is reduced to half
d. Two-cycle of DNA replication occurs
Solution: Meiosis is a type of cell division in which the number of chromosomes is cut in half, resulting in four haploid cells. DNA replication is followed by two rounds of cell division in...
Which of the events listed below is not observed during mitosis?
a. Chromatin condensation
b. Movement of centrioles to opposite poles
c. The appearance of chromosomes with two chromatids joined together at the centromere.
d. Crossing over
Solution: The parent cell's replicated chromosomes condense and become thousands of times more compact during prophase than they were during interphase. These structures now look like X-shaped...
Which of the events listed below is not observed during mitosis?
a. Chromatin condensation
b. Movement of centrioles to opposite poles
c. The appearance of chromosomes with two chromatids joined together at the centromere.
d. Crossing over
Solution: The parent cell's replicated chromosomes condense and become thousands of times more compact during prophase than they were during interphase. These structures now look like X-shaped...
Cells which are not dividing are likely to be at
a. G1
b. G2
c. Go
d. S phase
Solution: Cells that do not divide further exit G 1 and enter the quiescent stage (G 0 ) of the cell cycle, which is an inactive state. Cells in this stage are still metabolically active, but they...
A bivalent of meiosis-I consists of
a. Two chromatids and one centromere
b. Two chromatids and two centromere
c. Four chromatids and two centromere
d. Four chromatids and four centromere
Solution: The two homologous chromosomes that have been duplicated join, produce a bivalent. Tetrad is another name for it, and it is created mostly during the pachytene stage of...
Mitosis is characterised by
a. Reduction division
b. Equal division
c. Both reduction and equal division
d. Paining of homologous chromosomes
Solution: Mitosis is characterized by equal division since the number of chromosomes in the daughter cells remains the same as in the parent cell. Meiosis, on the other hand, is characterized by...
Meiosis occurs in organisms during
a. Sexual reproduction
b. Vegetative reproduction
c. Both sexual and vegetative reproduction
d. None of the above
Solution: The fusion of two gametes, each with a complete haploid set of chromosomes, is required for sexual reproduction to produce offspring. These gametes are made up of specialized diploid cells...
At which stage of meiosis does the genetic constitution of gametes is finally decided
a. Metaphase I
b. Anaphase II
c. Metaphase II
d. Anaphase I
Solution: Since chromosomes are separated in anaphase 1 and 2n from the parent becomes n in daughter cells, the genetic constitution of gametes is finally determined in the Anaphase 1 stage. So, the...
Meiosis results in diploid organisms
a. Production of gametes
b. Reduction in the number of chromosomes
c. Introduction of variation
d. all of the above
Solution: Meiosis is a cell division process that results in the halving of the number of chromosomes, resulting in the creation of gametes. In pachytene (prophase I, meiosis I), the crossing...