Algae, Tree, Herbs, Bush, Shrub, Grasses, Vines, Fern, Moss, Spermatophyta, Bryophyta, Fern Ally, Flower, Photosynthesis, Eukaryote, Prokaryote, carbohydrate, vitamins, amino acids, botany, lipids, proteins, cell, cell wall, biotechnology, metabolities, enzymes, agriculture, horticulture, agronomy, bryology, plaleobotany, phytochemistry, enthnobotany, anatomy, ecology, plant breeding, ecology, genetics, chlorophyll, chloroplast, gymnosperms, sporophytes, spores, seed, pollination, pollen, agriculture, horticulture, taxanomy, fungi, molecular biology, biochemistry, bioinfomatics, microbiology, fertilizers, insecticides, pesticides, herbicides, plant growth regulators, medicinal plants, herbal medicines, chemistry, cytogenetics, bryology, ethnobotany, plant pathology, methodolgy, research institutes, scientific journals, companies, farmer, scientists, plant nutrition
Select Language:
 
 
 
 
Main Menu
Please click the main subject to get the list of sub-categories
 
Services offered
 
 
 
 
  Section: Genetics » Physical Basis of Heredity » The Chromosome Theory of Inheritance
 
 
Please share with your friends:  
 
 

Physical Basis of Heredity 4. The Chromosome Theory of Inheritance

 
     
 
Content
Physical Basis of Heredity 4. The Chromosome Theory of Inheritance
Association of paternal and maternal chromosomes at meiosis
Qualitative differences between chromosomes
Formulation of chromosome theory
Sex chromosomes and chromosome theory
In Mendel's Laws of Inheritance, Lethality and Interaction of Genes, Quantitative Inheritance and Multiple Alleles (Based on Classical Concept of Allelomorphism), basic principles of heredity have been outlined. In Physical Basis of Heredity 1.  The Nucleus and the Chromosome, a discussion on the nucleus and the chromosomes has been presented and in Physical Basis of Heredity 2.  Cell Division (Mitosis and Meiosis), cell division responsible for growth, reproduction and transfer of hereditary traits from one generation to another has been discussed. The mechanism of inheritance is so precise that one would like to know about the physical counterparts associated with heredity. In this section, we will discuss briefly the evidence, which became available in early part of the present century to demonstrate that hereditary factors were located on chromosomes.

Soon after the rediscovery of Mendel's laws in 1900, W.S. Sutton (an American graduate student) and T. Boveri (a German biologist), in 1903, independently showed a parallelism between behaviour of chromosomes and Mendelian characters.
The similarities included the following and are shown in Figure 9.1. (i) The chromosomes occur in pairs like the alleles of a gene, (ii) The homologous chromosomes separate during meiosis like the pair of similar or dissimilar alleles of a gene separate at the time of gamete formation, (iii) Different chromosomes orient and separate independently during meiosis, showing parallelism with Mendelian factors. It was therefore, concluded that genes or the Mendelian factors were located on chromosomes. This generalization is now known in the form of chromosome theory of inheritance, which should be distinguished carefully from chromosomes theory of sex determination. As a requirement for validity of chromosome theory, precise and regular distribution of genes from cell to cell can be explained on the basis of mitosis. Similar distribution from generation to generation can be explained through mitotic division. On the basis of knowlege of mitosis and meiosis presented in previous sections, Mendel's principles, particularly the segregation principle can be explained in the form of chromosome theory of inheritance, where describing chromosome theory of inherttance, all avilable evidences in favour of chromose theory will not be included in this section but some though be discussed at appropriate places in other different sections of Genetics.

Parallelism between Mendel's hypothetical particles (genes) and chromosomes during meiosis.
Fig. 9.1. Parallelism between Mendel's hypothetical particles (genes) and chromosomes during meiosis.


Mendel, while analysing his results, was quite unaware of details of cell division and, therefore, did not talk of physical counterpart of his factors. The physical basis of inheritance was later worked out by a number of workers. The relevant works will be briefly described here in the same sequence. Mendel, while analysing his reults, was quite unaware of details of cell divisionand, therefore, did not talk of physical counterpan of his factors. The physical basis of inheritance wis later worked out by a number of workers. The latevant works will be briefly described here in the same sequence in which the evidences can be suggesting that Mendelian factors are located on chromosomes.



 
     
 
 
     




     
 
Copyrights 2012 © Biocyclopedia.com | Disclaimer