Hobble

You share 50% of your genes with a sibling, but 90% of your species' gene pool with mice.

I am in favour of genetic engineering. I believe it could allow for a huge breakthrough in human evolution. I don't advocate "designer babies", where you pick blonde hair, green eyes, 6' tall, etc., but if could eliminate genetic diseases through manipulation of some sort, then why not. Humans are not under the same pressures of natural selection as we once were. Our survival is no longer dependent on our physical fitness, leading to some impairments to increase in the gene pool (ie. poor eye-sight, however I know this is not necessarily purely genetic, due to increase in amount of reading and strain on the eyes). If we could correct these through gene therapies, then it would compensate for the lower level of natural selective pressure.

Are the two alleles of the gene the same (ie. homozygous) or different (heterozygous)? If the latter, then miRNA could in fact work.

My very first post on these boards, so I figure I should start with a relatively easier topic From what I can take away from your original post, it seems like you are getting Mitosis and Meiosis mixed up. Mitosis is when each chromosome is replicated followed by cell division, so each daughter cell has one copy of each chromosome that originally came from the 'mother' cell. Meiosis is when all the chromosomes pair up into 23 autosomal pairs and 1 sex chromosome pair. The pairs then separate during Anaphase and following cell division, form two haploid gametes. These gametes (from the mother) then fuse with gametes from another individual (from the father) to reform a diploid cell with the full complement of chromosomes.