Download App

Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance5 Marks
Question

Shown above is the electron micrograph (EM) picture of 'beads-on-string'.
  1. Identify and explain the detailed structure of a bead with the help of a labelled diagram.
  2. Describe the packaging of 'beads-on-string'in a eukaryotic cell.
✓

Answer

  1. The bead-like structures are the nucleosomes:
  1. There is a set of positively charged proteins, called histones, rich in basic amino acid residues, lysine and arginine.
  2. Histones are organised to form a unit of eight molecules, called histone octamer.
  3. The negatively charged DNA is wrapped around the positively charged histone octamer, to form a nucleosome; a nucleosome contains 200 bp of DNA helix.
  1.  
  1. The nucleosomes form the repeating units of the chromatin fibre in the nucleus; these nucleosomes of a chromatin are seen as the beads-on-string structure under electron microscope.
  2. The chromatin fibres are further coiled and condensed at metaphase stage to form the chromosomes.
  3. The packaging of chromatin at higher levels requires another set of proteins, called non histone chromosomal (NHC) proteins.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Answer the following questions in detail." from Molecular Basis of Inheritance→Molecular Basis of Inheritance — all question types→BIOLOGY STD 12 Science question papers→Maharashtra Board STD 12 Science question papers→Maharashtra Board question paper generator→

Similar questions

$F_1$​​​​​​​–generation does not resemble either of the parents.
→
What are the most common warning signs of drug and alcohol abuse among youth ?
→
Give the graphical representation of pleiotropy to show inheritance of Sickle-cell anaemia.
→
What are the different types of reflexes?
→
Give the graphical representation of test cross and back cross.
→
Proliferative Phase and Secretory Phase.
→
Complete the table-Related to outbreeding devices.
Type Description Example
1. ____________________ Unisexual flowers/Monoecious or dioecious plants  Papaya,

 Maize 
2.____________________  Mechanical device to prevent Self-Pollination - Natural physical barrier  ________
3. Prepotency _____________________________ Apple
 4. Heteromorphy  _____________________________ Primula
5. Protandry Androecium matures earlier than gynoecium ________
→
Explain the contribution of Alfred Sturtevant in ‘Chromosome mapping’.
→
Describe the process of respiration in man.
OR
Describe the mechanism of respiration in human beings.
→
What is meant by traditional knowledge? What is its importance?
→