Elementary Biology

anonymous:

Often, in your attempts to seem scientifically literate, you emphasize the zygote’s unique DNA code, claiming that gives it personhood. Either say monozygotic twins are the same person or admit there is more to being human than DNA. Doubt you will publish this as it presents a difficult question. As a biologist and I promise that you have the most elementary concept of what you are talking about.

cultureshift:

I appreciate your ability to split hairs, and I have never claimed to be a biologist. Not killing prenatal children really only requires common sense, not science, but I will entertain your question.

I have never claimed that an embryo required unique DNA from any other human being to argue for personhood. My point has always been that because an embryo has different DNA than his or her mother, he or she cannot be another organ belonging to the mother. I have only made this point because some less educated abortion advocates claim that prenatal children are no different than their mother’s liver or kidneys. Pointing out that a zygote has unique DNA from his or her mother whereas her organs contain only her DNA illustrates this difference. It also highlights the fact that an embryo is a living human being that will eventually develop into adulthood, not just a ‘clump of cells’.

To further split hairs with you, research published in the American Journal of Human Genetics in 2008, determined that monozygotic twins do possess differences in their DNA due to copy-number variation.

The exploration of copy-number variation (CNV), notably of somatic cells, is an understudied aspect of genome biology. Any differences in the genetic makeup between twins derived from the same zygote represent an irrefutable example of somatic mosaicism. We studied 19 pairs of monozygotic twins with either concordant or discordant phenotype by using two platforms for genome-wide CNV analyses and showed that CNVs exist within pairs in both groups. These findings have an impact on our views of genotypic and phenotypic diversity in monozygotic twins and suggest that CNV analysis in phenotypically discordant monozygotic twins may provide a powerful tool for identifying disease-predisposition loci. Our results also imply that caution should be exercised when interpreting disease causality of de novo CNVs found in patients based on analysis of a single tissue in routine disease-related DNA diagnostics.

Though this is irrelevant to whether a human embryo deserves human rights, I thought you might find it interesting. Of course, further deviation between monozygotic twins occurs through epigenetic variances in gene expression over time, but this does not change the underlying sequence of the gene itself. And in case you were unaware, monozygotic twins have unique fingerprints due to differences in environmental factors within the amniotic sacs affecting phenotype.

Sources: The American Journal of Human Genetics, The New York Times

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