Does the DNA sequence of a butterfly match that of the caterpillar it used to be?

Question

Just had this thought occur to me. If one were to take a DNA sample(or is it RNA?) of a caterpillar before it became a chrysalis, and attempt to match the sample against one taken after the chrysalis matured to a butterfly, would the two samples come up identical?

Answer 1

I believe the answer lies in transcriptional regulation. For example, a human blastocyst will have the same DNA composition as a fetus, infant and adult human. What differs, however, is the transcription of certain genes over others. For example, what separates a liver cell from a muscle cell? What separates an early embryonic cell from an adult somatic cell? In all the above cells, the DNA sequence would be identical. However, if you were to look at transcription, some genes would be 'on' some would be 'off'. In a very simplified overview of the process, an illuminating example that could help understand is the mechanism of testosterone. Within the nucleus of cells, AR (androgen receptors) are DNA-binding transcription factors (proteins that assist in transcription). When an androgen (such as testosterone) binds to the AR, it causes a conformational change in the AR such that dimerization is possible (the joining of two identical proteins, in this case, AR). AR dimers can then bind directly to DNA and up-regulate genes that result in male sexual phenotypes that were otherwise 'silent' prior to puberty. However, a DNA sampling test from a prepubescent male with those genes effectively 'turned off' and post-pubescent male with those genes 'turned on' would be identical, even though there is obvious structural difference between the two. The difference however comes in which genes are transcribed, and that can have a profound impact on the phenotype. I apologize if this is long and convoluted, but I would imagine that the process of such drastic phenotypic change in between two developmental stages would be at least somewhat similar in a butterfly, so as a result, the DNA would be identical, but the transcriptome would differ.