Definitions [2]
Definition: Crossing Over
Mutual exchange of blocks of homologous genes between a pair of homologous chromosomes is known as crossing over.
Definition: Mutation
Mutation is a sudden change in one or more genes, or in the number or in the structure of chromosomes.
or
Mutation is a phenomenon which results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism.
Key Points
Key Points: Mutations
- A mutation is a sudden heritable change in DNA sequences that leads to changes in the genotype and phenotype of an organism.
- Loss of DNA segment = deletion; gain of DNA segment = insertion/duplication; both cause chromosomal aberrations, commonly seen in cancer cells.
- Frame-shift mutation - caused by loss or gain of a DNA segment; Point mutation - change in a single base pair (e.g., sickle cell anaemia).
- Physical mutagens that cause mutation include UV radiation, X-rays, alpha, beta and gamma rays; Chemical mutagens include mustard gas, phenol and formalin.
- Mutation is an important source of genetic variation in organisms, alongside recombination.
