"Mutation; A gene mutation is a permanent change in the DNA sequence that makes up a new allele in the population. Mutation range in size from change in a single DNA nucleotide to a large segment of a chromosome or whole chromosomes or or sometime change in the number of chromosomes. the agents that cause mutations are called mutagens while the organism or cell in which mutation occurs is called mutant. source and Types of Mutation; There are many types of mutation which are basis deferent type of mutation. Source of Mutagens; the sources of mutation may be physical , chemical and biological agents. physical mutagens include radiation of any kind i ,e Uv gamma rays, X-rays, radioactive rays, high temperature alteration. the chemical mutagens include colchicine , mustard gas , nitrous gas, acridine organs, reactive radioactive isotopes, and free oxygen particles etc.. Biological mutagens may include certain viruses , transposons and errors that occur during meiosis or DNA replication. Types of Mutation; creation or origin of mutation is called mutagenesis. Based upon mutagenesis, there are two types of mutation. the mutations which occur naturally and Automatically due to internal or external factors are called spontaneous mutations, whereas mutations which are produced by external factors for the establishment of new varieties of organisms are called induced mutations . mutations are of two types on the basis of where the mutations occur and to what extent. A mutation that causes change of single or few -nucleotides in the DNA is called point mutation, whereas the mutations that cause change in the structure or number of chromosomes are called chromosomal mutations or aberration. Harmful Aspects of Mutation; A mutation that decreases the fitness of the organism in the environment is called harmful mutation. A mutation is sometime a form of adaptation , but if something mutation could possibly be harmful to it cause serious effect, are many such examples like, (1); born without a part of brain.(2); Cancer is a firm of a harmful mutation , (3); the developmental abnormalities , such as microcephaly , cleft palate, causes of abnormal number of chromosomes ( Down syndrome , Klinefelter syndrome, Turner syndrome etc.) and heredity disorders like sickle cells anaemia etc. Useful Aspects of Mutation; Mutations are also considered as a contributing factors towards evolution. changes the gene controlling development can have major effect on the morphology of the adult organisms. Because these effects are so significant, scientist suspect that changes in developmental genes have helped bring about large - scale evolutionary transformation . Developmental changes may help to explain , for example, how some hoofed mammals evolved ocean - dwellers , how water plants invaded the land, and how small , armoured invertebrates evolved wings . Mutation are considered as the driving force of evolution , where less favourable mutation we removed from the gene
pool by natural selection, while more favourable (beneficial or advantageous) ones tend to accumulate."
