I liked the video above because it describes gene regulation in both prokaryotic and eukaryotic cells. The visual displays were highly beneficial to the understanding of the processes he speaks about. I particularly liked that the video references both the lac operon and the trp operon, both of which we discussed in class. The pictures were very clear, and helped me understand the topic better. Both negative and positive controls are discussed, and overall the video is thorough, clear, and concise. At only 10 minutes in length, it is certainly worth watching if anyone is having difficulty understanding some of the more general concepts regarding gene regulation.
Click here for a link to vocabulary words on prokaryotic gene regulation. It may help you remember some terms found in this chapter if you are a person who uses flashcards as a learning tool.
If you are having difficulty understanding the trp operon, which is perfectly understandable, click here to access a tutorial on the subject. It includes images, animations, and a quiz at the end to ensure that anyone can benefit from using the tutorial. The animation is step-through as well as narrated, and may help you understand the topic if the book simply is not doing it for you.
There are several methods of controlling gene expression in eukaryotes, of which methylation is one. This is a tool in epigenetics that allows cells to "turn off" genes. Epigenetics is the control of genes by factors not related to an individual's DNA sequence. These types of tools determine what proteins are ultimately translated and function. Preserving chromosome stability, genomic imprinting, and embryonic development all involve DNA methylation, and errors in methylation have been linked to several serious human diseases. Early experiments with 5-azacytidine, which inhibits DNA methyltransferase enzymes, allowed scientists to investigate how DNA methylation impacts cell differentiation and gene expression.
DNA methyltransferase enzymes convert the cytosine bases of eukaryotic DNA to 5-methylcytosine. This cytosine is located next to a guanine nucleotide. DNA methylation's exact role in gene expression is currently unknown, although it is possible that it blocks promoters to which transcription factors would otherwise bind. Methylation of promoters has been linked to low or no transcription. There are differences in methylation levels in different tissue types as well as between normal and cancerous cells.
Histone methylation patterns have been found to change dramatically through the cell cycle. Some studies have shown that DNA and histone methylation are connected, such as in studies that show DNA and histone methylation working together to ensure that proper methylation patterns are passed on to daughter cells during translation. Sometimes, when DNA is methylated, deacetylation occurs in nearby histones. This allows for a stronger inhibition of transcription. Similarly, DNA that is not methylated does not attract deacetylation enzymes to nearby histone proteins. Methylation is generally a long-term process, but it can also allow for "epigenetic reprogramming".
Research is currently being conducted into the connection between methylation errors and diseases, including lupus, cancer, and muscular dystrophy. Tumor suppressor genes have been found to be silenced in cancer cells due to hypermethylation. Overall, methylation rates in cancer cells are much higher than in normal cells. In certain cancers, hypermethylation can be a marker for diagnosing cancer, as it may be detectable in early stages of the cancers.
Click here for the link to the article from which I retrieved my information.
To start off with, the most commonly accepted plural form of the word "octopus" turns out to be "octopuses". "Octopi" and "octopedes" have also been used as plural forms, but they are more objectionable. In my blog, I will be referring to more than one octopus as octopi simply because I think it sounds better, no matter how objectionable the term may be. And also because I can.
Genetic mutations are responsible for the existence of complex creatures. The complexity of creatures can also be attributed to RNA editing, in which enzymes are altered without impacting organisms' genetic blueprints. RNA editing has allowed organisms to regulate essential functions, including the development and function of nervous systems. Octopi have provided evidence suggesting that this type of editing has allowed them to adjust to external, environmental changes in addition to internal changes. Researchers have investigated how this editing has allowed octopi to live in warm and cold bodies of water. These editing tools have helped them acclimate to different environments.
Cephalopods have been seen doing much RNA editing. Different processes can be fine-tuned in different organisms with the same genetic makeup. Since octopi are cold-blooded, temperature differences can have an impact on neural pathways. Nervous system communication is dependent on neural firings. These firings are started by sodium-ion channels and stopped by potassium-ion channels. Both of these channels slow down in cold temperatures, with the potassium-ion channels slowing significantly more than sodium-ion channels. RNA editing plays a role here, as one Antarctic octopus's editing locations allowed for an increase in the rate of the potassium channel closing. This allowed for the channels to become closer in rate. Other species of octopi, such as those living in Arctic and tropical waters, have also displayed RNA editing.
There is more than one response to the environment that requires RNA editing, and it certainly does not stop with temperature regulation. Scientists have discovered about 100 editing sites in just eight mRNAs. They are also editing the RNA that edits, allowing for greater diversity in enzymes that edit.
Click here to access the article from which I retrieved my information.
