Epigenetic changes involving methylation can directly affect the phenotype of an individual or her offspring by                   . a. causing correlations between parents and children; b. causing changes to the DNA that affect gene expression but not DNA sequence; c. generating low heritability; d. increasing the likelihood of monozygotic twinning; e. sterilizing the DNA

Video transcript

Welcome back. Here's our next question. How do epigenetic modifications such as DNA methylation affect normal gene function. So epigenetic modifications are changes uh to they change the activity of a DNA segment but they changed that activity without changing the DNA sequence itself. And that's really important without changing. Because when you change the D. N. A sequence that's a mutation. So that's how the epigenetic modifications differ from mutation. So we changed the activity of the D. N. A segment how it's expressed but we don't change the base pair sequence. Now an example of one of these is we will call for more content video DNA methylation which is the addition of a methyl group to the D. N. A molecule or more than one method group and that changes the DNA sequence because when it occurs in a gene promoter it actually silences the gene by blocking it's transcription. So when that methyl group is there in the promoter region it stops transcription and that gene doesn't get expressed. So with that in mind let's look through our answer choices. Choice A says it causes insertion into the genetic sequence. Well that is not our correct answer because we discuss that epigenetic modifications do not change the D. N. A sequence. So that would be a mutation not an epigenetic modification. Choice B says it adds an unnecessary amino acid in the growing polyp peptide chain. This is not an answer either. Um epigenetic modifications or modification at the DNA level. They don't have anything to do with the later translation of the protein choice C says it causes problems in M. RNA splicing. That's not our answer, that's not the mechanism of epigenetic modification. Um it silences a gene by blocking transcription, not by affecting the splicing of the M R N. A. So now we're down to Choice D. And, yes, it causes gene silencing and that's because the addition of the methyl group in the promoter region blocks transcription of that particular gene. So once again, how do epigenetic modifications affect normal gene function? Choice D. It causes gene silencing. Hope to see you in the next video.