Table of contents | |
Introduction | |
Inheritance of One Gene | |
Inheritance of Two Genes | |
Exceptions to Mendelism | |
Genetic Disorders | |
Genetic Code |
Gregor Johann Mendel (1822-1884)
Mendel, a scientist and monastery worker, is famous for his groundbreaking work on pea plants, which led to the formulation of fundamental laws of genetics, now known as Mendel’s laws of inheritance. Although his work was not initially recognized, it later became the cornerstone of modern genetics.
One allele can be dominant over another, and this dominant allele will be expressed in the offspring.
During gamete formation, alleles separate so that each gamete carries only one allele for each trait.
When observing two traits simultaneously, this is called the inheritance of two genes, and the cross is a dihybrid cross. Mendel’s Law of Independent Assortment explains this type of inheritance.
Allele pairs separate independently during gamete formation, meaning the inheritance of one trait does not affect the inheritance of another. Mendel deduced this principle from dihybrid crosses, such as those involving seed color and pod color, which produced an F2 generation ratio of 9:3:3:1.
Mendel’s observations and laws illustrate that the inheritance of one character does not influence the inheritance of another, confirming the independent assortment of traits.
A gene is a small segment of DNA on a chromosome that codes for a polypeptide. This concept, known as the one gene-one polypeptide theory, was proposed by Lederberg and Tatum. During inheritance, genes tend to stay together, a phenomenon known as linkage. The formation of new combinations of genes different from those of the parents is called recombination.
At the time of inheritance, due to various complexities, some genetic disorders can occur in progeny organisms lead to various diseases. A list of these disorders, with their details in given below:
Genetic codes are sequences of three nitrogenous bases, such as AUG, GUG, and UUG, which correspond to specific amino acids and play a crucial role in protein synthesis (translation). The central dogma explains the utility of the genetic code.
D Baltimore (1970) also described the presence of reverse transcriptase enzyme in RNA tumour viruses. Its presence changed the central dogma of protein synthesis into central dogma reverse, which looks like
According to data from the Human Genome Project (HGP), the human genome comprises approximately 40,000 genes, each responsible for various functions in the human body.
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1. What is the inheritance pattern of genetic disorders? |
2. How many genes are typically involved in determining a specific trait? |
3. Can exceptions to Mendel's laws occur in genetic inheritance? |
4. What is the significance of the genetic code in understanding inheritance patterns? |
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