Genetics

Genetics Definition

Genetics is a biological field focused on studying heredity and its biological processes, including genes, genomes, and the cell cycle.

What is Genetics?

Genetics is the study of how traits are inherited from parents to offspring. Inheritance is the foundation of heredity, the process by which characteristics are passed down from one generation to the next. Gregor Johann Mendel is known as the “Father of Modern Genetics” for his discoveries on the basic principles of heredity.

Variation refers to the differences between offspring and their parents. It can be observed in the behavioral, cytological, physiological, and morphological characteristics of individuals within the same species.

Also Read: Human Reproductive System

Some of the major reasons for variation include genetic or chromosomal rearrangement, mutated genes influenced by the environment, and crossing over. For more detailed information, let's delve into genetics notes to understand genes and the principles of inheritance.

Genes

Principles of Inheritance

When Mendel observed the monohybrid cross, he formulated two laws of inheritance:

Law of Dominance

Distinct elements, known as factors, govern characteristics. These factors always occur in pairs, with one gene of the pair dominating over the other.

Law of Segregation

Alleles do not blend; instead, the two characteristics are recovered throughout gamete formation (in the F2 generation). The characters separate from each other and are passed on to different gametes. Homozygous individuals produce similar types of gametes, while heterozygous individuals produce diverse gametes with varied characteristics.

Explore More: Male Reproductive System

Incomplete Dominance

After Mendel's work, the discovery of incomplete dominance revealed a situation where neither allele displays a dominant trait, resulting in a blend or a middle ground between the characteristics of the alleles.

Codominance

In cases where two alleles lack a dominant-recessive relationship, they both affect the organism simultaneously.

Law of Independent Assortment

This law states that the separation of one set of characteristics is independent of another set when they are combined in a hybrid.

The Chromosomal Theory of Inheritance

Genes and chromosomes exist in pairs, with homologous chromosomes containing two alleles of a gene pair at corresponding sites. The coupling and separation of chromosomes result in a corresponding split of the genes they carry, known as the Chromosomal Theory of Inheritance.

Read More: Female Reproductive System

Sex Determination

Henking observed a specific nuclear arrangement present in only half of the sperm, which he termed as X. It was later found that ova that received only X chromosomes developed into females, while those that did not receive an X chromosome became males. This led to the X-chromosome being identified as a sex chromosome, with the others termed autosomes.

Mutation

The occurrence of a modification in DNA that leads to variations in the phenotype and genotype of an organism is termed a mutation.

Genetic Disorders

Disorders of a chromosomal nature include:

  • Down’s syndrome.
  • Klinefelter’s Syndrome.
  • Turners Syndrome.

Disorders of a Mendelian nature include:

  • Haemophilia.
  • Sickle Cell Anaemia.
  • Phenylketonuria.

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Frequently Asked Questions on Genetics

Ans. The Three types of genetics are - single-gene, chromosomal, and multifactorial.

Ans. Traits or characteristics, like eye color and blood type, are inherited by children from their parents through genetic transmission.

Ans. Gregor Johann Mendel is known as the father of genetics. 

Ans. Genetics involves the examination of how genes and traits are transmitted from one generation to another.

Ans. Rosalind Franklin