How do chromosome pairs get "paired up" for protein synthesis?

Question

If my understanding is correct, during interphase a normal human cell will have 46 chromosomes scattered about in the cell nucleus. These chromosomes can be thought of as pairs: there are two copies of "chromosome 1", one from mom and one from dad. Same goes for chromosome 2, chromosome 3, ... chromosome 22. Although we think of these as coming in pairs, are they actually attached or paired up in some way?At some point, protein synthesis will take place via transcription. What I'm having trouble understanding is how and when the above pairing takes place. Does transcription occur independently for each of the 46 chromosomes? I don't think this is the case, because in my head I imagine that we will only get one set of proteins from the *pair of each chromosome*. Also, I'm unclear as to how dominant/recessive genes can come into play unless protein synthesis occurs as a function of both pairs of chromosomes.I hope this is clear enough. Thanks.

Answer 1

What you are asking about is gene expression, not the physical pairing of chromosomes. And the answer is...it depends.

Your body is able to mark certain chromosomes for use and others for disuse. For instance, one of each X chromosome in each cell of a female is made into an inactive form called a Barr Body. In each cell, however, a different X may be inactivated.

In autosomes, either chromosome may be used. For instance, individuals may have AB blood because both the A allele on one chromosome and the B on the other are being expressed. In some cases, in a given cell, one chromosome's allele may be more likely to be expressed than another because of modification of the DNA after replication.

There is also evidence that in some cases, your body may deliberately target certain members of autosome pairs to be inactivated, but that is still being researched for a clearer understanding.