Chromosomal Theory of Inheritance
Mendel’s work was not accepted at that time because due to a lack of communication between the scientific communities, the use of maths in his work was not acceptable to some biologists, lack of physical proof of his work on the genes, etc. reasons. Then after years of his death, his work was rediscovered by three scientists namely Carl Correns, Hugo De Vries, and Von Tschermrk independently. They were able to do so due to the development of a microscope so that cell division and its chromosomes were observable.
Based on the work done by the above three scientists to rediscover Mendel’s work Walter Sutton and Theodore Boveri noted that the behavior of chromosomes was parallel to the behavior of genes and they used chromosome movement to explain Mendel’s Laws. Based on this development they proposed the Chromosomal Theory of Inheritance. The salient features of this theory were;
- Chromosomes are responsible for the transmission of heredity.
- Two identical chromosome forms a homologous pair.
- During gamete formation, this homologous pair segregates.
- Independent pairs of homologs segregate independently from each other.
- The behavior of chromosomes is parallel to the behavior of genes because genes are located on chromosomes.
Experimental verification of this theory was done by T.H. Morgan, who worked with fruit flies (Drosophila melanogaster). He chose fruit flies because;
- They can grow easily on a simple synthetic medium with very basic nutrients.
- They have a very short life span i.e. around 2 weeks.
- A single mating produces a large number of progenies.
- There is a clear difference between males and females i.e. females are larger than males.
- Many types of hereditary variation can see n with a low-power microscope.
Principles of Inheritance and Variation CBSE Notes for Chapter 4
Inheritance is the term given to the process by which characters are passed from parents to offspring which forms the basis of heredity. Heredity is the process of passing down genetic traits from parents to offspring. The degree of difference in characters between a parent and offspring is called variation. All these are studied under genetics which deals with the study of inheritance and variation of characters passed from parents to offspring. The first proper documented study of this inheritance and variation was done by G.J. Mendel which is why he is considered the father of genetics.
In a living cell, the chromosomes of a particular gene are present in a diploid manner and each one is called an allele. Genotype is the genetic make-up of an organism i.e. the TT or tt. Whereas phenotype is the external morphological appearance or expression of the genotype i.e. TT phenotype will be tall and for tt phenotype will be dwarf.
Table of Content
- Mendel’s Laws of Inheritance
- Inheritance of One Gene
- Inheritance of Two Genes
- Chromosomal Theory of Inheritance
- Linkage and Recombination
- Pleiotropy and Polygenic Inheritance
- Sex Determination
- Mutation
- Pedigree Analysis
- Genetic Disorders
- CBSE Previous Year Question Papers
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