Factor V Leiden

Factor V Leiden-  Hereditary Hypercoagulability

• Hypercoagulability: excessive blood clot formation
• Factor V Leiden: a mutation in Factor V protein
• Factor V is pro-coagulation protein
• When activated Factor V acts as a co-factor in activation of protombin to thrombin by factor Xa 
• Factor V is inactivated by activated protein C
• Type of mutation: missense mutation  G->A [ arginine -> glutamine]
• this mutation disable inactivation of Factor V by protein C
• this leads to excessive fibrin clots
• Diagnosis: PCR-RFLP (PCR of fragment gene followed with restriction of the product)
• Normal: Factor V gene has two restriction site by MnlI

                             ____67____|___37___|______163______

• three fragments are produced (163, 67, 37 bp)
• Mutant: Factor V gene has one restriction site by MnlI (the mutation destroys the second restriction site for MnlI endonuclease enzyme)
• two fragments are produced (200, 67 bp)

                           _____67____|_________200____________

• The fragments then run on a gel

Fragile X Syndrome (trinucleotide repeat disorder)

• Genomic location of mutation: Xq27.3
• Type of mutation: trinucleotide repeat of CGG
• Normal range of the repeats: 6-50
• Intermediate number: 50-199 possess a premutation
• Fragile X repeats: >200 
• Diagnosis: screening with PCR followed by Southern blot
• PCR is not efficient with hight number of CGG repeats
• Prognoses: The large the number of the CGG repeats the earlier the onset of symptoms; more severe symptoms
• Mode of the mutations: the CGG repeats become methylated at the C nucleotide; methylation silences the gene
• a carrier is phenotypical normal in part because of the lack of FMR1 methylation

Quiz: Detection and Identification of Microorganisms

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Quiz: DNA Polymorphisms and Human Identification

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