Hi, now we are going to discuss a very important topic in genetics, chromosomal theory of inheritance in which we will discuss how flow of genetic information occurs from one generation to the next generation and how chromosomes are involved in this process.
Table of Contents
Basic Information About Chromosome:
Chromosomes are like a vehicle in genetics through which the genetic information passes from parents to progeny generation after generation, chromosomes are condensed forms of chromatin.
The Chromosomal Theory of Inheritance:
When it was not clear how genetic traits were transferred from one generation to the next generation, two scientists, Suton and Boveri, gave their chromosomal theory of inheritance which was the basis theory of inheritance.
In this theory they explained actually what part of cell contain the genetic information, they explained that the gene are the basic unit of genetics because the gene is responsible for a specific traits and the gene present on the chromosome as a portion on the chromosome.
Before the chromosomal theory of inheritance people only knew that genetic traits are transferred from one generation to the next generation but it was unknown how it occurs because then the idea of genes was not known to people.
Mendel through his experiment showed different types of opposite characters expressed in different generations but then it was unknown how the genetic characters expressed and how they transferred into the next generation.
But with the advancement in technology people come to know about a special structure in the cell, chromosome and then different scientists start to find the factors of genetic information and finally their research proves that genes are the basic unit of genetic information.
With time when we find different advanced technology to observe the cell structure very clearly then we see that the chromosome segregation occurs during the time of cell division and the Medel theory gives us the chromosomal theory of inheritance.
Linkage and Recombination:
According to the law of segregation of Mendel no preference should be observed during the segregation of genes during crossing over, gene segregation occurs randomly but in the experiment of Morgan random segregation did not occur which indicates that during the segregation of genes some specific factors determine their segregation.
During the time of meiosis cell division crossing over occurs which causes exchange of genes among chromosomes and it changes the combination of genes on a chromosome which is known as genetic recombination.
But exchange of these genes among the chromosome is sometimes restricted which is known as linkage and this linkage is most prominent when two genes occur on the chromosome at very close.
This fact can be easily proven by observing the character of different generations and measuring the frequency of genetic recombination by gene mapping and it gives us an idea about the position of genes on the chromosome.
Chromosomal Theory of Inheritance and Its Observations:
- During meiosis cell division, the homologous chromosomes move without affecting other pairs of homologous chromosomes; every pair of homologous chromosomes move independently.
- During cell division any chromosome of a homologous pair passes to any gametic cell and it occurs randomly no preference is observed during passing of a chromosome into a certain gamete.
- During formation of gametes each gamete receives one chromosome of a pair of homologous chromosomes so in all homologous pairs of chromosomes one set of chromosomes goes to each gamete.
- During the fusion of gametes and fertilization in the zygote cell contribution of each gamete is equal because each gamete contributes to the same number of chromosomes, though size and morphology of male and female gametes are different but their number of chromosomes is the same.
- During the formation of gametes the number of chromosomes becomes half that of the parent cell but when they fuse again by the process of fertilization the number of chromosomes restore again in the new individual as their previous parents cells.
Read More: Differences Between Autosomes and Allosomes
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