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Parahemophilia is an autosomal recesive disorder ch. by a reduced plasma concentration of the factor 5 bloood coagulation protein. deficiency arises from a 12 base pair deletion in the factor 5 gene that impairs the secretion of factor5 by hepatocytes and result in an abnormal accumulation of immunoreactive factor 5 antigen in cytoplasm. in which region of the factor 5 gene would this mutation most likely be located? plz explain in a simple language. a}5"untranslated region b}first exon c}middle intron D} last exon e}3'untranslated region
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d) last exon as if i is first there wuld nt be any protein at all
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B. fisrt exon (signal peptide is located at N-ternimus)
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First exon ... some of the N-terminal Hyrdrophobic Signal Sequence peptides have been removed ... this makes targeting of AA diffcult....AA cannot be drasfered to the Endoplasmic reticulum ... this was discussed in Kaplan Biochem chapter on translation !!
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i think the exon which they are talking is in the DNA and it does not involve the protein translation or post translational modification. All exons express protein and introns do not here since the deletion is in the gene which controls factor 5 sectretion results in dec protein expression from these exons so what they want us to know is whther protein exp is a function of exons or introns........well answer is exons and next what they want us to know is the effects of first exon deletion vs del of last exon.......well if there is a deletion at the first exon well there wont be any protein 5 exp at all but q stem says it is reduced so it has to be last exon where the deletion has taken place resulting in reduced protein exp
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The Factor V expression is not reduced, but accumulated at cytoplasm in this case. The sereted proteins contain a signal sequence (about 15 AA) at their N-terminal for leading protein secretion from RER to extracelullar space. If DNA seqeunce at signal peptide site mutated or delected, the protein can be expressed but not secreted. just like this case. Also, the deleted DNA is exactly 12 bp, means 4 AA lost at protein level which doesnot change open reading frame, but enough cause signal peptide disfunctional.
