Definition:
A gene is a functional unit attached to the chromosomal thread that can pass from one cell to another and can be transmitted from one generation to another without any change in its chemical and physical nature.
Introduction:
A Gene is a hereditary unit (also called hereditary factors of Mendel) and is responsible for inheritance. Its physical and chemical nature is foundation stone of all genetic principles. Gene is a part of DNA and is made up of nucleotides. It is an ultimate unit of Recombination. Genetic information is conveyed from DNA to MRNA.
Gene term was coined by Johanson (1909)
Location :
Located on the chromosomal thread which runs throughout the chromosome. The total number of genes that are present on the haploid set of chromosome represents one Genome. (Human genome is 3.2 billion b.p)
- Chemically, gene contains DNA as a primary component.
Subtitle 1 : Gene (DNA) serve as genetic material because it satisfies following criteria :
1) It can duplicate itself via Replication and is precisely distributed among new cells by cell division.
2) Undergoes Mutation and such changes are stably inherited.
(i.e. it can accept some minor changes, and such changes keep on accumulating and finally help in evolution of cells, organisms to a new form)
3) It is able to express genetic information to mRNA via Transcription and finally produce proteins.
Subtitle 2 : Each gene occupies a specific position in a specific chromosome. This specific position is called Locus. Genes are arranged on chromosomes, in linear sequences, like beads on the thread at a fixed distance.