Biology

Cell Cycle and Chromosomes

1,219 Questions

Explore a curated list of questions covering the cell cycle, mitosis, and meiosis. Topics include DNA replication, chromosomal structures, and genetic disorders. This material is essential for students preparing for biology and general science competitive exams.

Cell cycle eventsDNA replicationMeiosis processChromosomal structuresGenetic disorders

Cell Cycle and Chromosomes Questions

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Sometimes a few chromosomes have non staining secondary constriction at a constant location. This gives the appearance of a small fragment, called : 

  1. NOR

  2. Satellite

  3. Telomere

  4. kinetochore
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Certain chromosomes possess a secondary constriction at a constant specific location, which is non-staining and gives the appearance of a small chromosomal fragment separated from the main body. This distinct morphological feature is known as a satellite, and chromosomes possessing it are called satellite chromosomes.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Which of the following statements is incorrect?

  1. Every chromosomes essentially has a secondary constriction

  2. The interphase nucleus has a loose and indistinct network of nucleoprotein fibres called chromatin
  3. A single human cell has approximately $2.2$ metre long thread of DNA distributed among its forty six chromosomes

  4. Chromatin contains DNA and some basic proteins called histone, some non histone proteins and also RNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Not all chromosomes have a secondary constriction; only specific chromosomes (SAT-chromosomes) possess them. The other statements correctly describe chromatin, DNA length, and composition.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

What would be the number of chromosomes of the aleurone cells of a plant with $42$ chromosomes in its root tip cells?

  1. $21$
  2. $42$
  3. $63$
  4. $84$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Root tip cells are diploid (2n), so 2n = 42, which means the haploid number n = 21. Aleurone cells in endosperm are triploid (3n) because they are formed by triple fusion. Therefore, the number of chromosomes in aleurone cells is 3 * 21 = 63.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Chromosome consists of

  1. DNA only

  2. DNA and histone protein

  3. DNA, histone proteins and non-histones proteins

  4. DNA and non-histones protein
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Chromosomes are made up of DNA and protein. Histone and non-histones proteins are associated with chromosomal DNA. Histone participate as structural components and provide strength and stability and protect DNA from shearing and breakage while the non-histones act as functional or regulatory components either in activation or repression of genes.

So, the correct answer is option C.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Chromosomes are composed of

  1. DNA, RNA, histones, non-histones

  2. DNA and histones

  3. DNA and RNA

  4. DNA, RNA and histones
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Chromosomes are composed of DNA, RNA, histones, non-histones. A chromosome is a packaged and organized chromatin, a complex of macromolecules found in cells, consisting of DNA and protein. The functional segments of DNA are known as genes. The DNA-bound macromolecules are proteins, which serve to package the DNA and control its functions.

So, the correct answer is option A.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

The non-sticky chromosomal ends are known as

  1. Chromatids

  2. Centromere

  3. Chromomere

  4. Telomere
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The telomeres do not have any overhanging ends of nucleotides so it is known as non sticky chromosome ends called telomere. A telomere is a region of repetitive nucleotide sequences at each end of a chromatid, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. 

So, the correct answer is option D.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Bead like structure found on chromosome are called as

  1. Chromomeres

  2. Chromonemata

  3. Chromonema

  4. Centriole
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A chromomere  is one of the serially aligned beads or granules of a eukaryotic chromosome, resulting from local coiling of a continuous DNA thread. It is visible on a chromosome during the prophase of meiosis and mitosis. The chromomeres are present during leptotene phase of prophase I during meiosis. During zygotene phase of prophase I, the chromomeres of homologs align with each other to form a homologous rough pairing. These chromomeres help provide a unique identity for each homologous pairs.

So, the correct answer is option A.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Exceptionally, large chromosome is

  1. Lampbrush chromosome

  2. Polytene chromosome

  3. Megachromosomes

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All chromosomes mentioned are large chromosomes. These chromosomes are producing large amounts of RNA for the oocyte, and most of the genes present in the DNA loops are being actively expressed. Each lateral loop contains one or several transcription units with polarized RNP-matrix coating the DNA axis of the loop.The majority of the DNA, however, is not in loops but remains highly condensed in the chromomeres on the axis, where genes are generally not expressed. This is about lampbrush chromosomes, the polytene and mega chromosomes are also larger than the other normal chromosomes.

So, the correct answer is option D.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Which chromosomes are called as supernumerary?

  1. B-chromosome

  2. Sex chromosome

  3. Double minutes chormosome

  4. Lampbrush chromosome
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

B chromosomes are called supernumerary or accessory chromosomes. It is because these chromosomes are not considered as essential for being normal. These are not found in every individual. During alloploids, it suppresses homologous pairing which reduces multiple pairing between homologous chromosomes in allopolyploids.  

So, the correct option is A.

Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Swellings present over the chromosomes are

  1. Centromeres

  2. Centrosome

  3. Puffs

  4. Chromomeres
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids
During mitosis, spindle fibers attach to the centromere via the kinetochore.
Centromeres were first thought to be genetic loci that directs the behavior of chromosomes
So, the correct answer is 'Centromeres'
Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Kinetochore is 

  1. Granule within centromere

  2. Surface of centromere

  3. Constriction near chromosome end

  4. End of chromosome
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The centromere is the lighter staining region on the chromosome of a cell which appears as a constriction.
They are also known as a primary constriction or kinetochore.
The kinetochore is a proteinaceous structure that assembles at the surface of the centromere which forms the site for binding of spindle fibres during cell division.
So, the correct answer is 'Surface of centromere'.
Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

A constriction on the chromosome is

  1. Centromere

  2. Centrosome

  3. Centriole

  4. Chromomere.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • The centromere is the lighter staining region on the chromosome of a cell which appears as a constriction.
  • They are also known as a primary constriction or kinetochore.
  • It is a specialized DNA sequence that links a pair of sister chromatids where the spindle fibres are attached during cell division.
  • It is responsible for the transfer of replicated chromosomes into the two daughter cells during the cell division.
  • So, the correct answer is 'Centromere'
Multiple choice botany the mitotic cell cycle chromosome and its structure chromosome nucleus and chromosome

Satellite means

  1. Terminal part of the chromosome beyond secondary constriction

  2. Terminal part of the chromosome beyond primary constriction

  3. Terminal part of chromosome beyond tertiary constriction

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Satellite chromosomes or SAT chromosomes are those chromosomes which have secondary constrictions other than a centromere.
  • The terminal end of the chromosome present beyond the secondary constriction is called satellite which is attached to the chromosome by a thin thread called chromatin.
  • So, the correct answer is 'Terminal part of the chromosome beyond the secondary constriction'.