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Assignment no.1Subject Trends in GenomicsTopic MutationsSubmitted To Dr. IbrahimSubmitted By Maham AtharRoll no. CIIT/FA17/RBS-005/SWLAssignment no.1 Subject Trends in GenomicsTopic MutationsSubmitted To Dr. IbrahimSubmitted By Maham AtharRoll no. CIIT/FA17/RBS-005/SWLMutations- Changes in the nucleotide sequence of DNA.- The replication and distribution of genetic material is extremely accurate so that the genetic information is usually passed on from one generation to the next without alteration.- But, occasionally errors do occur both during replication and distribution of the genetic material giving rise to sudden heritable changes in the characters of organisms such alterations are called mutations, while individuals showing these changes are known as mutants.- Mutations may be harmful. - Mutations may be beneficial. - Mutations may have no effect on the organism. - May occur in somatic cells (aren’t passed to offspring)- May occur in gametes (eggs & sperm) and be passed to offspring MutagensTwo types of mutagens are as follows1- Physical mutagensI. Ionizing radiations : particulate radiations , non-particulate radiationsII. Non-ionizing radiations : Alpha ,beta ,fast neutrons, thermal neutrons , X-rays, gamma rays , UV rays.2- Chemical mutagensI. Alkylating agents : acridine dyesII. Deamination agents : other chemical mutagens ,mustard gas, nitrogen mustard Classes of Mutations There are two types of mutations1. Spontaneous MutationsThey are mainly caused during DNA replication or by incorporation of incorrect nucleotide in the growing DNA chain .They occur naturally by changes in DNA sequence during replication.2. Induced mutation They are caused by the changes in DNA brought about by some environmental factor called mutagens. E.g UV light, x-rays, gamma rays etcTypes of Gene Mutation1- Point mutationsA mutation may arise due to a change in the base sequence of a gene. Such mutations are called as gene mutations or point mutations. Point mutation is a random SNP (single-nucleotide polymorphism) mutation in the deoxyribonucleic acid (DNA) that occurs at one point.  Missense mutationThis type of mutation is a change in one DNA base pair that results in the substitution of one amino acid for another in the protein made by a gene. Nonsense mutationA nonsense mutation is also a change in one DNA base pair. Instead of substituting one amino acid for another, however, the altered DNA sequence prematurely signals the cell to stop building a protein. This type of mutation results in a shortened protein that may function improperly or not at all. Silent mutationIt codes for the same amino acid. A silent mutation has no effect on the functioning of theprotein. 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. This is possible because 64 codons specify only 20 amino acids. Frameshift Mutation Inserting or deleting one or more nucleotides. Changes the“reading frame” like changing a sentence. Proteins built incorrectly e.g The fat cat ate the wee rat. Frame Shift (“a” added): › The fat caa tet hew eer at.2- Chromosomal mutationsChanges in chromosomal number and structure also produce heritable changes in phenotype these are termed as chromosomal mutations. Types of Chromosomal mutationsFive types are as follows I. DeletionA deletion changes the number of DNA bases by removing a piece of DNA. Small deletions may remove one or a few base pairs within a gene, while larger deletions can remove an entire gene or several neighboring genes. The deleted DNA may alter the function of the resulting protein.II. DuplicationA duplication consists of a piece of DNA that is abnormally copied one or more times. This type of mutation may alter the function of the resulting protein.III. Inversion Chromosome segment breaks off. Segment flips around backwards. Segment reattaches IV. Translocation Involves two chromosomes that aren’t homologous. Part of one chromosome is transferred to another chromosomesV. Nondisjunction Failure of chromosomes to separate during meiosis. Causes gamete to have too many or too few chromosomes. Disorders are  Klinefelter’s Syndrome – XXY chromosomes  Down Syndrome – three 21st chromosomes  Turner Syndrome – single X chromosomeMutations based on functional effect of changea. Morphological Mutants This type of mutations generate a visible morphological alterations. e.g shape, colour & size.b. Lethal Mutants They are fatal in nature leading to the death of individuals.c. Conditional mutants Conditional mutations are normal under one condition (permissive), but abnormal under another (restrictive).d. Biochemical mutants These mutations cause loss or of some biochemical or nutritional function in the cell.Diseases caused by MutationCystic fibrosis A defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene causes cystic fibrosis (CF). A protein made by this gene controls the movement of the water and salt in and outof the body's cells. Genes in people with CF incorrectly code proteins. This causes thick, sticky mucus and very salty sweat. Color blindnessPeople who are colorblind have mutations in their genes that cause a loss of either red or green cones. Genetic changes involving the@OPN1LW@or@OPN1MW@gene cause red-green color vision defects.@Blue-yellow color vision defects result from mutations in


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COMSATS BIO 111 - Mutations

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