Negative Dominant Mutation

[glykon]

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Could anyone pls explain the FA2011 example of dominant negative mutation? What is the Tx factor?
Sorry if the q is silly, but I'm no Genetics genius...

 

[Belleza156]

I dont have FA2011 with me but i just did a Kaplan question where an examlple of dominant negative mutation was marfans.

"Dominant negative mutation produces gene product that acts antagonistically w the normal gene product. Classic example is marfans, in which the mutant fibrillin disrupts microfibril formation, even though the other fibrillin gene encodes the normal protein"

 

[Phloston]

I've seen a Kaplan question with the Marfan's as well, but I've also seen two practice questions on osteogenesis imperfecta. You need to know that type-I, the most common type, is null-allele effect, not a negative-dominant mutation, but that the ones which are fatal in utero (i.e. types II-4, I believe) are dominant-negative. Be extra watchful for that. If the child is alive with OI (typical presentation of school-age child with fractures) --> null-allele. If the woman has had multiple miscarriages and then has a child (who is likely not to live long) --> dominant-negative.

 

[glykon]

Thanks, guys, that is really interesting.
What I found in FA2011 and couldn't understand is the following example of dominant negative mutation:
"Mutation of Tx factor (??) in its allosteric site. Nonfunctioning mutant can still bind DNA, preventing wild-type Tx factor from binding."

 

[Phloston]

Thanks, guys, that is really interesting.
What I found in FA2011 and couldn't understand is the following example of dominant negative mutation:
"Mutation of Tx factor (??) in its allosteric site. Nonfunctioning mutant can still bind DNA, preventing wild-type Tx factor from binding."

Transcription factor

 

[Aclamity]

Thanks, guys, that is really interesting.
What I found in FA2011 and couldn't understand is the following example of dominant negative mutation:
"Mutation of Tx factor (??) in its allosteric site. Nonfunctioning mutant can still bind DNA, preventing wild-type Tx factor from binding."

A dominant negative mutation, in a nutshell, is basically a heterozygous mutation (one normal gene producing normal protein, and one mutated gene producing mutant protein), where the mutant protein inhibits the actions of the normal protein
In your example, the mutant Tx factor inhibits the actions of the normal Tx factor by binding to the DNA and blocking the normal Tx factor from binding

This is in contrast to normal heterozygous mutations where the mutated gene either (a) doesn't produce protein, or (b) produces a nonfunctional protein that has no significant effect on the function of the non-mutated gene

 

[glykon]

Thank you so much, that was very helpful!