Mutation bsc
- 2. Introduction • Sudden heritable change in genetic material or character of an organismis known as mutation • Individuals showing these changes are known as mutants • An individual showing an altered phenotype due to mutation are knownas variant • Factor or agents causing mutation are known as mutagens • Mutation which causes changes in base sequence of a gene are knownas gene mutation or point mutation
- 3. A mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extra chromosomal DNA or other genetic elements. Mutations result from errors during DNA replication or other types of damage to DNA The two main causes of mutation are MISTAKES IN CELLREPLICATION During replication of DNA, double strands of DNA are separated. Each strand is then copied to become another double strand. About 1 out of every100,000,000 times, a mistake occurs during copying, which can lead to a mutation.
- 4. ENVIRONMENTAL FACTORS . Mutations can also be caused by environmental foes. Tobacco, ultraviolet light and other chemicals (Hydroxylamine Base analogs etc ) Alkylating agents are all potential enemies of DNA These agents cause the DNA to break down. This is not necessarily unnatural — even in the most isolated and pristine environments, DNA breaks down.
- 5. History • English farmer Seth Wright recorded case of mutation first time in 1791 in male lamb with unusual short legs. • The term mutation is coined by Hugo de Vries in 1900 by his observation in Oenothera. • Systematic study of mutation was started in 1910 when Morgan genetically analyzed white eye mutant of Drosophila. • H. J. Muller induced mutation in Drosophila by using X- rays in 1927 ; he was awarded with Nobel prize in 1946.
- 6. Characteristics of Mutation • Generally mutant alleles are recessive to their wild type or normal alleles • Most mutations have harmful effect, but some mutations are beneficial • Spontaneous mutations occurs at very low rate • Some genes shows high rate of mutation such genes are called as mutable gene • Highly mutable sites within a gene are known as hotspots. • Mutation can occur in any tissue/cell (somatic or germinal) of an organism
- 7. Classification of mutation • Based on the survival of an individual 1. Lethal mutation – when mutation causes death of all individuals undergoing mutation are known as lethal 2. Sub lethal mutation - causes death of 90% individuals 3. Sub vital mutation– such mutation kills less than 90% individuals 4. Vital mutation -when mutation don’t affect the survival of an individual are known as vital 5. Supervital mutation – This kind of mutation enhances the survival of individual
- 8. • Based on causes of mutation 1. Spontaneous mutation- Spontaneous mutation occurs naturally without any cause. The rate of spontaneous mutation is very slow eg- Methylation followed by deamination of cytosine. Rate of spontaneous mutation is higher in eukaryotes than prokaryotes. Eg. UV light of sunlight causing mutation in bacteria 2. Induced Mutation- Mutations produced due to treatment with either a chemical or physical agent are called induced mutation . The agents capable of inducing such mutations are known as mutagen. use of induced mutation for crop improvement program is known as mutation breeding. Eg. X- rays causing mutation in cereals
- 9. • Based on tissue of origin 1. Somatic mutation- A mutation occurring in somatic cell is called somatic mutation. In asexually reproducing species somatic mutations transmits progeny to the next progeny 2. Germinal Mutation- from one When mutation occur in gametic cells or reproductive cells are known as germinal mutation. In sexually reproductive species only germinal mutation are transmitted to the next generation
- 10. • Based on direction of mutation 1.Forward mutation- When mutation occurs from the normal/wild type allele to mutant allele are known as forward mutation 2.Reverse mutation- When mutation occurs in reverse direction that is from mutant allele to the normal/wild type allele are known as reverse mutation
- 11. • Type of trait affected 1. Visible mutation- affects on phenotypic character Those mutation and can be which detected by normal observation are known as visible mutation 2. Biochemical mutation- mutation which affect the production of biochemicals and which does not not show any phenotypic character are known as biochemical mutation
- 13. Chromosome Mutations • May Involve: – Changing the structure loss or gain
- 14. . A chromosome aberration, or mutation is a missing, extra, or irregular portion of chromosomal DNA. It can be from an atypical number of chromosomes or a structural abnormality in one or more chromosomes. There are many types of chromosome anomalies. They can be organized into two basic groups, numerical and structural anomalies.
- 15. Numerical disorders This is called aneuploidy (an abnormal number of chromosomes), and occurs when an individual either is missing a chromosome from a pair( monosomy) or has more than two chromosomes of a pair (trisomy, tetrasomy etc.). In humans, an example of a condition caused by a numerical anomaly is Down Syndrome, also known as Trisomy 21
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- 18. ii. Structural abnormalities . When the chromosome's structure is altered, this can take several forms: 1. DELETION 2. DUPLICATION 3. INVERSION 4. TRANSLOCATION
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- 20. Chromosome Mutations • Five types exist: –Deletion –Inversion –Translocation – Nondisjunction –Duplication
- 21. Deletio n • Due to breakage • A piece of a chromosome is lost
- 22. Inversio n • Chromosome segment breaks off • Segment flips around backwards • Segment reattaches
- 23. Duplicati on • Occurs when a gene sequence is repeated
- 24. Translocati on • Involves two chromosomes that aren’t homologous • Part of one chromosome is transferred to another chromosomes
- 25. Translocati on
- 26. Nondisjuncti on• Failure of chromosomesto separate duringmeiosis • Causes gamete to have too many or too few chromosomes • Disorders: – Down Syndrome – – Turner Syndrome – – Klinefelter’s Syndrome –
- 27. A gene mutation is a permanent alteration in the DNA sequence that makes up a gene, such that the sequence differs from what is found in most people. Mutations range in size; they can affect anywhere from a single DNA building block (base pair) to a large segment of a chromosome that includes multiple genes.
- 28. Gene mutations are heritable changes in the base sequence of individual genes or genomic DNA ,which may produce allelic alterations in the genotype. Since they occur within indl genes,they are also called intragenic mutations or point mutations in distinction with chromosome mutations(changes in chromosome structure.) and genome mutations (changes in chromosome number) . The frequency of spontaneous gene mutations increased by several factors. Defective DNA repair system defective DNA replication system Defective DNA polymerases and DNA ligase production of aberrant DNA precrsors.
- 29. POINT MUTATION A point mutation is a type of mutation that causes a single nucleotide base substitution, insertion, or deletion of the genetic material, DNA or RNA. Causes of point mutations Causes of point mutations Point mutation is a random SNP (single-nucleotide polymorphism) mutation in the DNA. A single point mutation can change the whole DNA sequence. spontaneous mutations that occur during DNA replication. The rate of mutation may be increased by mutagens
- 31. . Functional categorization Nonsense mutation: Code for a stop, which can truncate the protein. A nonsense mutation converts an amino acid codon into a termination codon. This causes the protein to be shortened because of the stop codon interrupting its normal code.base pair subtitution- Missense mutation: It is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It is a type of nonsynonymous substitution
- 32. .S.ilent mutations: Code for the same amino acid. A silent mutation has no effect on the functioning of the protein. A single nucleotide can change, but the new codon specifies the same amino acid, resulting in an unmutated protein. This type of change is called synonymous change, since the old and new codon code for the same amino acid.
- 33. Types of Gene Mutations• Include: –Point Mutations Affect only the indl genes located in small portions of chromosomes,hence the name – Base pair Substitutions –Insertions –Deletions –Frameshift
- 34. Point Mutation • Change of a single nucleotide • Includes the deletion, insertion, or substitution of ONE nucleotide in a gene
- 35. Point Mutation • Sickle Cell disease is the result of one nucleotide substitution • Occurs in the hemoglobin gene.HbA Valine instead of
- 36. Gene mutations are classified under two general classes-frame –shift mutation and base-pair substitutions. fewer than 20% of the spontaneous mutations are due to base-pair substitutions. mostly by frame shift mutation.
- 37. Frameshift Mutation • Inserting or deleting one or more nucleotides • Changes the “reading frame” like changing a sentence • Proteins built incorrectly
- 38. A frameshift mutation (also called a framing error or a reading frame shift) is a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that is not divisible by three.
- 39. Frame shift mutation-or sign mutation or reading frame mutation are gene mutations which bring about a shift in the reading frame of codons through changes in the no and order of nucleotides(base pairs) . They involve insertion or deletion of one or more nucleotide pairs.Non-functional enzymes produced .More deleterious than sustitution mutations.
- 40. Base-pair substitution mutation-are the mutations in which one kind of nitrogenous base of a codon of DNA or mRNA is substituted by another kind.or by a base derivative. Some sbstitution mutation generate non-sense codons ,which will not specify any amino acids,but will serve as terminator codons. such substitution mutation are called non-sense mutations. Spontaneous base pair substitution occur by 3 processes Tautomerization,ionization,binding of base analogue.Ionization- of bases during DNA replication introduce transitional base pairs.It involves the lose of hydrogen atoms from the base. Transversion –purine replced by pyramidine. Transition—Purine replaced by purine .this is caused by Tautomerization,Base analogue,Deamination.
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- 42. Deletion mutation is a mutation in which a part of a chromosome or a sequence of DNA is lost during DNA replication. Deletions can be caused by errors in chromosomal crossover during meiosis , which causes several serious genetic diseases. e.g. Williams syndrome. Small deletions are less likely to be fatal; large deletions are usually fatal
- 44. Insertion mutation is the addition of one or more nucleotide base pairs into a DNA sequence. Insertions can be particularly hazardous if they occur in an exon, the amino acid coding region of a gene