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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.
Although we think of these as coming in pairs, are they actually attached or paired up in some way?
Chromosomes only pair up during metaphase I of meiosis. And meiosis only occurs during the production of gametes (sperm and oocytes). Say Chr1 from mom pairs up with Chr1 from dad. http://media.web.britannica.com/eb-media/76/94976-004-7D0416E7.gif">
About the chromosomes.
The chromosomes are not paired physically in the cell but yes, there is 23 chromosones, that have two copies of each, one from the dad, one from the mom. The homologous chromosomes are physically paired during meiosis, where cross-over of DNA will happen but only for a littel time.
About protein synthesis.
These are two cases in a recessive/dominant allele combination.
Both synthesize the protein, but the protein from the dominant gene will have the effect and the other just won't be able to.
The recessive gene transcription is blocked. The dominant can be the reason by synthesizing an inhibiting protein, or it could be a physical change to it's DNA etc.
This is only a small example since there is a large numbers of regulations that exists from the DNA, methylation of DNA, mRNA, transcription inhibition etc.
There is a lot more cases and exceptions since this is an extremely complicated subject. To learn all of them you would need a genetic book or a complete review on this subject.
Random monoallelic expression of autosomal genes: stochastic transcription and allele-level regulation
Chromatin regulation at the frontier of synthetic biology
RNA-mediated epigenetic regulation of gene expression