MUTATION PPT PDF biochemistry powerpoint
- 1. MUTATION VIKAS KUMAR ASSISTANT PROFESSOR DEPARTMENT OF BIOCHEMISTRY NMCH JAMUHAR
- 2. BI-7.3 Describe the gene mutation and basic mechanism of regulation of gene expression
- 3. MUTATION Mutation is defined as change in nucleotide sequence of DNA which act as a template for transcription and transmission of genetic information. There are four types of mutation 1. Point mutation 2. Frame shift mutation 3. Suppressor mutation 4. Read through mutation
- 4. POINT MUTATION Point mutation result from change in single nucleotide sequence They may be due to following changes i.e. Transition in which one purine base ( A ) is changed by another purine ( G ). Similarly ,a pyrimidine base ( C ) may be changed by other pyrimidine base ( T ) Other cause of point mutation is Transversion in which a purine base is changed by a pyrimidine and vice versa
- 6. Effects of Point Mutation Silent Mutation A point mutation may change the codon for one amino acid to a synonym for same amino acid. For example, CUA is mutated to CUC; both code for leucine. This mutation has no effect on the sequence of amino acid residues present in polypeptide chain.
- 7. Missense Mutation Mutation which results in change in sequence leading to different amino acid being incorporated in protein is called missense mutation
- 9. Nonsense Mutation Nonsense mutation refers to that mutation which result in the formation of a stop codon also called termination codon . This lead to the production of only a part of protein i.e. incomplete protein which is not functional. A tyrosine (codon, UAC) may be mutated to a termination codon (UAA or UAG)
- 10. Trinucleotide repeat expansion Occasionally, a sequence of three bases that is repeated in tandem will become amplified in number so that too many copies of triplet occurs. Protein produced in such scenario contains many extra copies of one amino acid. For example, expansion of the CAG codon in exon 1 of the gene for huntingtin protein leads to insertion of many extra glutamine residues in the protein, causing Huntington disease.
- 13. If the trinucleotide repeat expansion in untranslated region of gene, the result can be a decrease in amount of protein produced. Fragile X syndrome and myotonic dystrophy are example of such type of change.
- 15. Frame shift mutation Result from deletion or insertion of nucleotide in DNA that generates altered mRNA. Reading frame is garbled.
- 18. Cystic fibrosis Chronic, progressive, inherited disease that primarily affects the pulmonary and digestive system. Most commonly caused by deletion of three nucleotide from coding region of a gene, resulting in loss of phenylalanine at the 508th position in CFTR. Such change prevents normal folding of CFTR, leading to its destruction by the proteasomes. CFTR normally served as chloride channel in epithelial cell, and its loss result in formation of thick, sticky secretions in lungs and pancreas.
- 19. Manifestations of Mutations Lethal Mutations Silent Mutations Beneficial Mutations Carcinogenic Mutations
- 20. Triplet Repeat Disorders Myotonic dystrophy Huntington’s Disease Freidrich Ataxia Fragile X syndrome
- 21. REGULATION OF GENE EXPRESSION Synthesis of proteins under the influence of the gene is called the gene expression. All the genes coding for a protein are not expressed in all cell. Some gene are expressed almost always in all the cells. Induction??? Repression??
- 22. OPERON CONCEPT OF GENE REGULATION
- 24. REGULATION OF GENE BY REPRESSION
- 25. Methylation of cytosine residues will lead to silencing of genes. siRNA has an important role in gene silencing by induction of DNA methylation Steroid hormones plays an important role in gene expression by binding to HRE.