The accompanying chromosome diagram represents a eukaryotic ch...

Question

The accompanying chromosome diagram represents a eukaryotic chromosome prepared with Giemsa stain. Indicate the heterochromatic and euchromatic regions of the chromosome, and label the chromosome's centromeric and telomeric regions.

What term best describes the shape of this chromosome?

Are you more likely to find the DNA sequence encoding the digestive enzyme amylase in a heterochromatic, euchromatic, centromeric, or telomeric region? Explain your reasoning.

Accepted Answer

Hi, everyone. Let's look at our next problem. The heterochromatin or dark G bands are chromosomal areas that contain a lot of genetic information. Which of the following does not indicate the importance of dark G bands on chromosomes. Choice A, they contain genes that are actively transcribed. Well, since the dark G bands are primarily made up of heterochromatin, this is not correct. We'll put false here. The heterochromatin is tightly packed, which means that it's not accessible to transcription machinery. And therefore, there's very few genes in that hetero chromatic region. Um Most of the genes there, there are very few genes there to begin with. Uh because anything that's there is most likely silenced or expressed at very, very low levels. So, since we're looking for the one that does not indicate the importance of the dark GB N S, we're most likely to be looking at choice A which is not correct, but to be thorough, we'll look at our other answer. Choices. Choice B says they help to prevent, protect the ends of chromosomes from degradation. Well, this is true because along with heterochromatin, the dark G bands also contain telomeric DNA and those telomeres are those parts at the end of the chromosomes, they're a rich and they help protect the chromosomes from degradation just by being these extra bits at the end, since a little bit of information is lost every time those chromosomes are replicated. So that provides sort of this wiggle room to prevent important genes from being degraded as a person or an or an organism ages. So choice B is an important function of dark G bands. So that will not be our answer here. Then Joy C says they're involved in the regulation of gene expression. This is also true because the heterochromatin that makes up those dark G bands, uh generally does not contain genes that are transcribed. It also affects um nearby genes and will suppress their expression as well. So it's involved in preventing or suppressing gene expression. So that's also not our answer choice since it is a function of the dark bands. And finally, choice D they assist in chromosomal structure and function analysis. Well, this is also true. Um every chromosome as an individual banding pattern and as a result of each chromosome having this distinctive pattern, deviations from the pattern you expect to see can show the presence of genetic disorders, those distinctive patterns can also show information about genes, gene location and structural elements on the chromosome. So choice D also not our answer. So again, when we talk about the heterochromatin or dark G bands, which of the following does not indicate the importance of dark G bands on chromosomes choice A, they contain genes that are actively transcribed. See you in the next video.

Key Concepts

Euchromatin vs. Heterochromatin

Centromere and Telomere

Gene Location and Function

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