Biochemical structure of dominant vs recessive gene

[Murdstone]

Most all familiar with the terms dominant and recessive trait in a general way. I have seen little on the biochemical difference.

Assume

1. Gene codes for characteristic
2. Variance in characteristic due to sequence within gene

How does the structure of an allele differ from an actual different gene?
What is the biochemical mechanism behind dominant vs recessive?

 

[Ygggdrasil]

Here's a site with some useful information on the subject:

http://www.thetech.org/genetics/ask.php?id=227

Here are two previous PF threads discussing the issue further:
https://www.physicsforums.com/showthread.php?t=614620
https://www.physicsforums.com/showthread.php?p=3744324#post3744324

Let us know if you have any more questions after you read through these links.

 

[Murdstone]

How forgetful. I see I have dwelt on the question before. However, this time, after reflection, I have a better understanding of the process. The "recessive" gene is a mutation that codes differently for a protein. It might not code for a protein at all or it might code for a different "flavor" of the protein. So the gene itself is not the determinate of the trait. It is a precursor to the protein, with the protein being the tangible component that determines the trait.

To clarify. I was thinking that when a dominate and recessive gene "meet", that the dom silences the rec and that is it. Not so.

 

[Ygggdrasil]

To clarify. I was thinking that when a dominate and recessive gene "meet", that the dom silences the rec and that is it. Not so.

In most cases this is true. When an individual contains both a recessive and a dominant allele, it is usually not the case that the dominant allele interferes with the function of the recessive allele. Rather, the dominant allele just "overpowers" the recessive allele. For example, if the dominant allele encodes for a certain color pigment and the recessive allele encodes a lack of pigment, the individuals will show pigmentation whenever they have at least one dominant allele and will only lack pigmentation when they have two recessive alleles.

An exception here would be the case of a dominant negative (DN) allele, but here the "silencing" occurs at the protein level where the protein produced by the DN allele will prevent the protein produced by the recessive allele from functioning correctly.

How forgetful. I see I have dwelt on the question before. However, this time, after reflection, I have a better understanding of the process. The "recessive" gene is a mutation that codes differently for a protein. It might not code for a protein at all or it might code for a different "flavor" of the protein. So the gene itself is not the determinate of the trait. It is a precursor to the protein, with the protein being the tangible component that determines the trait.

Some alleles contain mutations in regions that do not change the protein itself. For example, consider lactose intolerance. Early humans, like most other mammals, have the ability to digest lactose only in early age and this ability goes away in adulthood. Sometime in human evolution, a mutation occurred near the gene encoding the lactase enzyme responsible for digesting lactose. This mutation did not change the protein, but rather, it changed the regulatory DNA around this sequence, preventing the gene from being turned off in adulthood. The result here is the lactase persistence allele, a dominant allele encoding the lactose tolerance trait.

Thus, here is an example where the dominant allele of the lactase gene is the mutant form, not the recessive allele. Furthermore, the different flavor of the lactase gene differs not in the protein produced but in how the protein gets turned on and off during development.

 

[mazinse]

Most all familiar with the terms dominant and recessive trait in a general way. I have seen little on the biochemical difference.

Assume

1. Gene codes for characteristic
2. Variance in characteristic due to sequence within gene

How does the structure of an allele differ from an actual different gene?
What is the biochemical mechanism behind dominant vs recessive?

To simplify things other than chemical differences, the true difference between the two is in terms of function. One works at 100% efficacy, the other works less.