Most large protein complexes in mitochondria and chloroplasts ...

Question

Most large protein complexes in mitochondria and chloroplasts are composed both of proteins encoded in the organelle genome and proteins encoded in the nuclear genome. What complexities does this introduce for gene regulation (i.e., for ensuring that the appropriate relative numbers of the proteins in a complex are produced)?

Accepted Answer

Hello, everyone. Let's look at the next question. Some proteins present in mitochondria and chloroplast are encoded by the organelle genome while others are produced from the nuclear genome, which of the following statements best describes the mechanism involved in ensuring that each organelle contains mitochondria or chloroplast contains the appropriate relative number of proteins. Choice, a co activation of mitochondrial and chloroplast genes by different transcription factors. Choice B, selective degradation of mitochondrial and chloroplast proteins, ribosomes, choice C co regulation of organelle and nuclear genes by common transcription factors or co activators or choice d import of nuclear encoded proteins into mitochondria and chloroplasts by non-specific mechanisms. So we recall that mitochondria and chloroplast have their own separate genome, the M T DNA and the C P DNA that produces some of their proteins, but a good number of their proteins are also produced by the nuclear genome. So our question is asking us, how do the cells regulate this so that you have the correct amount of proteins that you're not having, you know, too much being generated by one set of genes or the other set of genes. So the answer we're looking for here is choice c co regulation of the organ and nuclear genes by common transcription factors or Coors. So the genes are located in two different places, but the same trans transcription factors, the same Coors act to regulate the transcription of those genes in the two different genomes. And this makes sense because using common factors means you can coordinate the amount of protein being produced by the two different genomes. So with that in mind, it's pretty easy to eliminate choice A which talks about co activation by different transcription factors that wouldn't have that coordinating effect since you'd be using different transcription factors. And then choice B, selective degradation of the proteins is not the method that is used. And then choice d import of nuclear encoded proteins into mitochondria chloroplasts. Well, this does happen, there are nuclear encoded proteins that are imported into the organelles um usually in the form of large protein complexes, but this isn't a way to make sure that they are the appropriate number of proteins. So it happens, but it's not the mechanism we're looking for. So that's why choice D isn't our answer. So again, which statement thus describes the mechanism ensuring that each organelle contains the appropriate relative number of proteins. Despite the fact that we have genes in both the nuclear genome and the organelle, genome. Choice C co regulation of organelle and nuclear genes by common transcription factors or co activators. See you in the next video

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