Nucleus, Biology

Assignment Help:

Nucleus -

  • Largest component of the cell.
  • Nucleus is double membrane bound dense protoplasmic body that controls cellular metabolism, enclose all the genetic information, and is able to transmit the same to the next generation.
  • Leeuwenheek first seen nucleus in fish R.B.C.
  • Robert Brown coined the name nucleus. Robert Brown observed nucleus in pollen grain and stigma cells.
  • Boveri indicated significance of nucleus in heredity.
  • J. Hemmerling while working on unicellular alga Acetabularia proved that nucleus regulates the activity of cytoplasm and also heredity.
  • Except mature mammalian R.B.C. and Sieve cell of phloem every living cell has a nucleus.
  • Procaryotes have incipient nucleus devoid of nuclear membrane, nucleolus and histone. Such type of nucleus is called nucleoid.
  • Details of nuclear structure, come to be known only after its study under electron microscope.
  • Nucleus of undividing cell is called interphase nucleus.

NUMBER, SIZE, POSITION & SHAPE

  • Normally a cell has single nucleus, this condition is called Uninucleate / Mononucleate / Monokaryotic.
  • Sometimes a cell may have two nuclei called Binucleate / Dikaryotic cell e.g. Paramaecium caudatum has one macronucleus and one micronucleus, macronucleus controls metabolic activities and micronucleus controls genetic information. Paramaecium aurelia isTrinucleate with one macronucleus and two micronuclei.
  • Multinucleate condition found in striated muscle cells, latex vessels, Opalina, Ascaris, polycaryoctes of bone marrow, fungi (Rhizopus) and algae (Vaucheria), which are formed by free nuclear divisions.
  • Multinucleate condition in plants is called Coenocyte (coenocytic) whereas multinucleate condition in animals is called Syncytium.Multinucleate condition present in slime molds is called Plasmodium. Cell wall less fungi is called plasmodium. Coenocytic condition is formed by repeating karyokinesis and Syncytium condition is formed by fusion of cells.
  • Nucleus usually occupies 20% of cells mass. Its size depend upon ploidy, cell maturity and cell function.
  • Nucleus lies near the geometric centre of the cell, peripharal nucleus present in adipocytes & plant cells.
  • Nucleus is rounded in young plants and polygonal in animal cells, oval or elliptical in mature plant cells.

 

 


Related Discussions:- Nucleus

Purchasing of service, Normal 0 false false false EN-IN...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Why is carbon monoxide toxic for humans, Q. Why is carbon monoxide toxic fo...

Q. Why is carbon monoxide toxic for humans? Hemoglobin "likes" carbon monoxide (CO) much more than it likes oxygen. When there is carbon monoxide in the inhaled air it binds to

Explain clinical analysis, Explain Clinical analysis Clinical analysis...

Explain Clinical analysis Clinical analysis:  This analysis includes a complete physical examination and a medical history. The physical examination begins with the patient's

Explain the concept of atoms are associated, What is the logical order in w...

What is the logical order in which the concepts of atoms, molecules, cells... up to biosphere are associated? Atoms form molecules that structure cells that form tissues that f

Nutrition, mode of nutrition in follow animal lizard,bird,grasshopper,rat

mode of nutrition in follow animal lizard,bird,grasshopper,rat

Do fishes present an closed or open circulatory system, Q Do fishes present...

Q Do fishes present an closed or open circulatory system? How many chambers does a fish heart have? How does blood flow throughout the fish body? As in every vertebrate the cir

Why is sub-culturing essential in plant tissue culture, Why is sub-culturin...

Why is sub-culturing essential in plant tissue culture? Explain the process of heterosis. How is it dissimilar from inbreeding depression? Where and how is urea produced in

What is the concept of mesonephric, What is the concept of Mesonephric? ...

What is the concept of Mesonephric? Replaces the pronephros during development and is retained as functional kidney in adult fish and amphibians. Formed posterior to pronephros

What is the condition for mendels second law to be valid, What is the condi...

What is the condition for Mendel's second law to be valid? Mendel's second law is only valid for genes located in dissimilar chromosomes. For genes situated in the same chromos

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd