Missense mutation and non-sense mutation (molecular biology)

Nonsense mutation: A nucleotide substitution that creates a new stop codon is called a nonsense mutation.
Missense mutation: Nucleotide substitutions in protein-coding regions that do result in changed amino acids are called missense mutations or nonsynonymous mutations.

1. Presentation PREPARED BY: SHAFQAT HUSSAIN AND SAMDANI MEHMOOD DISCIPLINE: BS MLT SUBJECT: MOLECULAR BIOLOGY LECTURER: SIR ANEES MUHAMMAD TOPIC: Nonsense And Missense mutation.

2. OUTLINE Introduction to Mutation Missense mutations Diagrammatical view Missense mutations Nonsense mutation Diagrammatical view of Nonsense mutation Difference Between Nonsense And Missense mutation.

3. Mutation A mutation is a change that occurs in our DNA sequence, either due to mistakes. when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.

4. Missense mutations Type of point-mutation. Nucleotide substitutions in protein-coding regions that do result in changed amino acids are called missense A change in the amino acid sequence of a protein may alter the biological properties of the protein.

5. Missense mutations A classic example of a phenotypic effect of a single amino acid change is the change responsible for the human hereditary disease sickle cell anemia. The molecular basis of the sickle cell anemia mutation is an AT → TA transversion causing the normal glutamic acid codon in the hemoglobin to be replaced with valine.

6. Nonsense mutation This type of Point 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. 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.

7. Difference Between Nonsense And Missense mutation Nonsense mutation A mutation in which a sense codon that corresponds to one of the twenty amino acids specified by the genetic code is changed to a chain-terminating codon Introduces a stop codon to the codon sequence at the site of mutation Results in a premature chain termination at the site of mutation Results in an incomplete or truncated protein Proteins produced are mostly non-functional Lead to genetic disorders including cystic fibrosis, beta-thalassemia, Duchenne muscular dystrophy (DMD), Hurler syndrome, and Dravet syndrome. Missense mutation A single base pair substitution, which alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position Introduces a distinet codon Results in a distinct amino acid, which is conservative or non-conservative Results in a conserved or non-conserved protein Proteins produced are either functional, non-functional. or they have a distinct function from the original protein Lead to sickle-cell disease. Epidermolysis bullosa, and superoxide dismutase 1 (SODI) mediated amyotrophic lateral sclerosis (ALS).

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