What genetic process is occurring in a puff of a polytene chromosome? How do we know this experimentally?

Video transcript

Hi, everyone. Let's take a look at this practice problem together. Blank are a site for the transcription of RN A present within the polite chromosome containing concentrated RN a polymerase enzyme. So this polite chromosome. What is it? Well, it is a, they're very large chromosomes and they're often found in the salivary glands of insects. So our question is asking us for the site where transcription occurs on the polite chromosome. So let's take a look at our options. We've got a ribosomes. Well, recall that ribosomes are located in the cytoplasm of a cell and they function to translate MRN A into proteins and polypeptides. So, a is gonna be wrong. Now, let's look at TSS and this literally stands for a transcription start site and we would think this would be the correct answer because it literally says the site of transcription. However, it doesn't specifically reference the polite chromosome or it's not specifically about the polite chromosome. And therefore this is actually not a correct answer. Let's look at d nucleus, nucleus is an organelle. It's an organelle within eukaryotic cells that contains the chromosomes. So d is gonna be incorrect as well. It's not a site of transcription. So we're left with B puff. So, a chromosome puff, now these are swellings and their swellings on the polite chromosome. And the reason why they swell is because the chromosome uncoils and is diffused at these sites. And that is where RN A polymerase is able to transcribe guinea into RN A. So B is the correct answer. All right, everyone. I hope you found this helpful and I'll see you for the next practice problem.