Can you get two proteins made from a heterozygous gene mutation? - (Dec/19/2007 )
If you find a heterozygous mutation in human genomic DNA, resulting in an amino acid change, which protein is produced? The mutant or wildtype form? Or can you get both?
I understand that there are dominant and recessive alleles and so theoretically, only one protein should be produced. But what if it is co-dominance ... are both forms translated and go into the real world?
What is the best way to find out the dominant form? Would you sequence the protein or can you look at which gene-form is inactive (is this epigenetic analysis)?
Also, if the heterozygous mutation is located in an intron, what can you deduce from that?
I was wondering because many studies in my field have published clinical correlations from heterozygous mutations, where they have not proven that the mutation is dominant. Many of the mutations/SNPs are located in introns and so no-one has yet performed functional studies.
It will be interesting to learn more about this.
Short answer, yes.
Long answer, usually the non-useful proteins are degraded at the mRNA stage or in early protein synthesis. Sometimes there are compensatory mechanisms that stop production of the mutant version and enhance production of the normal version, and frequently there is inactivation of the mutant version by methylation of the gene.
let's not forget some blood conditions that show mixed dominance (or, at least, both proteins showing up):
sickle cell trait;
beta thalassemia minor;
i think there's no general answer. i don't know exactly about cytosolic synthesized proteins, but for proteins which are sythesized at the ER-membrane, many mutations will lead to a protein which is retained in the ER and degraded by ERAD. the you will have a minor portion of this mutated protein in the ER (fastly degradeded) and a major portion of the functional protein at its normal cellular compartiment.
there are also mutations leading to a protein which is not retained in the ER, but transported to its normal compartiment. These are mainly enzymes with silent muations or enzymes without catalytic activity.