Gene expression in connection with allele and chromosomes

[akvarel]

Hello,
I have some problems with understanding of the gene expression in respect of different alleles and homologous chromosomes.
We have 23 pairs of chromosomes. One chromosome in a pair comes from mother, another from father. Those two chromosomes which form a pair are similar in respect of the genes. So, gene A is on the chromosome from mother and the same gene is on chromosome from father. The difference is in alleles, a number of alternative forms of the same gene or same genetic locus. There can be lots of alleles of one gene but one individual can carry at most two alleles of one gene.

​If there is a mutation on mother's chromosome, the healthy allele from father's chromosome will be expressed as well as a faulty allele from mother. BUT the individual will not be sick because he has a healthy proteins. Right?

What does dominant or recessive allele mean in respect of genetic sequence? If an individual has one dominant and one recessive allele, it means that he has inherited one gene but two different representations of this genes resulting in two different alleles. But still two chromosomes will be expressed, meaning, the gene from mother's chromosome and father's chromosome will be expressed. But how a dominant allele will suppress the recessive one? How it will be depicted on protein, or mRNA level?

 

Sorry for confusing and thank you in advance.
Katja

 

[Vexen]

Hi,

 

Your question pertains to the molecular mechanism of recessive and dominance among alleles. Mendelian genetics in light of modern genetics becomes somewhat confusing.

 

In short, genes interact in a complex manner and there is no single reason for dominance. A single allele may be dominant or recessive depending on other alleles.

 

 

Firstly, your analysis of mendelian genetics is somewhat simplistic. For example, there are various different forms of allele interactions such as codominance.

 

Secondly, Mendelian genetics fails to explain the reasons for dominance and recessive alleles. The reasons for dominance are explained by modern genetics. For example, one study showed that small RNA expressed by one allele suppressed the expression of another allele (look at the picture attached).

 

Hope this helps

Edited December 9, 2014 by Mikhail