Genetics is a very important part of biology. It helps us trace our origins and determine why we are the way we are. It also enables us to understand our ancestry and how we evolved. That’s why it’s important to study genetics as it’s an essential topic in competitive exams. Many researchers have discovered their theories about our genes. The chromosomal theory of inheritance is such a theory. The theory states that the carriers of our genetic materials are the chromosomes. Let’s study this theory, its origin, and how significant it is in the field of genetics.
The chromosomal theory of inheritance
The chromosomal theory of inheritance is alternatively known as the Boveri-Sutton chromosome theory. The main discovery of the chromosomal theory of inheritance was that it identified the chromosomes as the carriers of the genetic matter or the genes. This theory brought a drastic change in the field of genetics, and it wasn’t accepted quickly by society.
The chromosomal theory of inheritance was discovered a long time after Mendelian genetics. Hence, this theory helped to prove Mendel’s laws right. Let’s see how and who came up with this theory.
The origin of the chromosomal theory
The chromosomal theory of inheritance resulted from many scientists’ attempts to study and prove Mendel’s laws of genetics, which were discarded by society. Among them, two scientists named Walter Sutton and Theodor Boveri worked independently around 1902 to 1903 and were able to identify the behaviour of chromosomes during the Anaphase of the cell division.
The following were the key discoveries of each of the scientists.
- Boveri:
Theodor Boveri studied the sea urchins. He discovered that all the chromosomes had to be present for proper embryonic development.
- Sutton:
Walter Sutton worked with the grasshoppers. He discovered that the chromosomes existed in matching pairs, consisting of paternal and maternal chromosomes. The separation of these pairs takes place during meiosis.
- Further, Sutton also estimated that this theory might constitute the physical basis of the law of heredity of Mendel.
Before moving to the postulates stated by the Chromosomal theory of inheritance, let’s understand what exactly are chromosomes.
Chromosomes
We know that the cell is the fundamental unit of any life form. Most living organisms are made up of organs that are made up of tissues and are the fundamental units of tissues and cells.
However, the cell is also further divided into organelles.
- The cell consists of cytoplasm, plasma membrane, nucleus, mitochondria, etc.
- The chromosomes are present in the nucleoplasm inside the nucleus.
- The chromosomes carry the DNA, which is the genetic material of an organism.
The human body contains 23 pairs of chromosomes, so a total of 46 chromosomes. The first 22 pairs are similar in human males and females. However, the 23rd pair of chromosomes are the sex chromosomes that are different for males and females. The structure of chromosomes is complex and three-dimensional.
Human genome sequencing has given us a lot of information about all of the chromosome pairs.
All the genetic data that we inherit from our parents and other previous generations is through the genes that are situated on the chromosomes.
The postulates of the chromosomal theory of inheritance
The following observations were made by Boveri and Sutton in this theory:
- During meiosis, that is the process of cell division, the pair of chromosomes that are homologous move as separate structures, independent from the other chromosome pairs.
- The distribution of chromosomes into pre-gametes is pretty random from each homologous pair.
- The gametes synthesised by each parent make up only half of their chromosomal complement.
- The female gametes, which are eggs, are much larger in size than the male gamete, that is, the sperm, and differ in morphology. However, they contain the same number of chromosomes, and hence the genetic contribution of each parent in the progeny is equal.
- During the process of fertilisation, the gametic chromosomes of males and females are combined to produce offspring. The offspring contain the same number of chromosomes as their parents.
The significance of the chromosomal theory of inheritance
Significance of the theory:
- The theory that explained the behaviour of chromosomes during meiosis by Boveri and Sutton explained Mendel’s laws of inheritance.
- Their theory established that genes are found in specific places of chromosomes which is reflected in the modern diagram of the cell.
- The chromosomal theory of inheritance was backed up by observations made by Thomas Morgan during his study of fruit flies.
- This theory also explained some cases of mutations in various organisms.
Such is the chromosomal theory of inheritance by Boveri and Sutton.
Conclusion
The study of genetics helps us understand how inheritance works and study evolution. The chromosomal theory of inheritance is also such a fundamental theory in genetics which established that the chromosome is the centre of the genetic material in the cell. Along with this, the chromosomal theory also explains the behaviour of chromosomes during meiosis. The theory states that both male sperm and female egg contribute equally to the child’s genetic material. The distribution of chromosomes in the pre-gametes is random and comes from each homologous pair. Boveri and Sutton came up with this theory.