Sourav Pan is the founder and sole author of Biology Notes Online. He holds a Bachelor of Science (B.Sc.) degree and an M.Sc. in Microbiology from the University of Calcutta. He creates educational resources covering microbiology, immunology, biotechnology, genetics, cell biology, botany, zoology, and other life-science subjects.
His goal is to make complex biological concepts easier to understand through well-structured, student-friendly articles based on academic textbooks, peer-reviewed research, and authoritative scientific sources. In addition to writing new content, he regularly reviews and updates articles to improve their accuracy, clarity, and educational value.
What is Somatic Mutation? Definition of Somatic Mutation A somatic mutation is a genetic change that occurs in non-reproductive cells after fertilization, which typically does not get passed on to offspring. Causes of Somatic Mutation Several factors and stressors can contribute to somatic mutations. These can be categorized into endogenous factors, chemical mutagens, physical mutagens, … Read more
What is Induced Mutation? Mechanism of induced mutation Induced mutations occur when external agents, known as mutagens, alter the structure or sequence of DNA. These mutations can arise through several mechanisms that affect how DNA bases interact or replicate. Let’s explore the primary mechanisms responsible for induced mutations. Base Replacement by Base Analogs Base analogs … Read more
Mutations are changes in the genetic material of an organism. These alterations can occur in various ways, and they play a fundamental role in biological diversity and evolution. Broadly, mutations can be classified into two major categories: gene mutations and chromosomal mutations. Gene mutations, also known as point mutations, occur when a change takes place … Read more
What is Mutation? Definition of Mutation Mutation is a permanent change in the DNA sequence of a gene or chromosome, which can result from errors in replication or environmental factors and can affect an organism’s traits. Terminology of Mutation Characteristics of Mutation Classification and types of Mutation Causes and Mechanisms of Mutation Understanding the causes … Read more
What is Crossing over? Definition of Crossing over Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis, resulting in new combinations of genes. Characteristics of Crossing over At which stage Crossing over occurs? Types of Crossing over Crossing over can be categorized based on its … Read more
What is Two-Point Cross? A two-point cross is a genetic mapping technique used to determine the recombination frequency between two specific genes located on the same chromosome. In this method, a test cross is performed between a heterozygous individual (carrying two different alleles for the genes of interest) and a homozygous recessive individual (which has … Read more
What is Pedigree? What is Pedigree Analysis? Pedigree Analysis Definition Pedigree analysis is a genetic tool used to trace the inheritance patterns of traits or disorders through generations of a family, helping to predict the likelihood of their occurrence in offspring based on familial history. Basic Steps of Pedigree Analysis Pedigree analysis involves several systematic … Read more
What is Sex Determination? Definition of Sex Determination Sex determination is the biological process that establishes whether an individual will develop as male or female, typically governed by genetic, environmental, or a combination of factors. It involves mechanisms that direct the differentiation of gonads and the subsequent development of sexual characteristics. Methods for Sex Determination … Read more
What is Sex-linked Inheritance? Methods for Sex-linked inheritance Sex-linked inheritance refers to the transmission of genetic traits that are carried on the sex chromosomes, specifically the X or Y chromosome. These traits are inherited differently than those located on the autosomal chromosomes due to the unique nature of sex chromosome behavior. The two main categories … Read more
What is Chromosome? What is Chromosomal Theory of Inheritance? Observations of Chromosomal Theory of Inheritance The Chromosomal Theory of Inheritance provided a clear link between the behavior of chromosomes and Mendel’s laws of inheritance. It was supported by a series of critical observations that connected chromosomal behavior during meiosis with the inheritance patterns Mendel described. … Read more