Lesson #2: DNA Mutation & Nitrogen Bases
I will be covering how DNA mutates and the different kinds of mutations, the causes of DNA mutations, and the bases of DNA and RNA.
Hello, students. Welcome to your second lesson in rudimentary biology. A section of this topic has been suggested by a student, and I decided to take up on that suggestion and expand on it only infinitesimally. I have taken into consideration the feedback and support I have received after the first lesson, and I thank you all for speaking out on your thoughts. I have stated this before, but I would like to reiterate that I apologize if the lessons I give seem as unhelpful as the blocks of text they are. I do so wish I could provide illustrations through out, but due to formatting difficulties with Tumblr, I cannot.
If you have read the lesson brief, you will know that by the end of this lesson, I will have taught you how DNA sequences mutate, the different types of DNA mutations, what can cause DNA mutations, and DNA and RNA bases. Do note that this lesson will be rather short, so if you would like me to go over a topic that will constitute a longer lesson, feel free to provide suggestions, my students.
Let us begin.
Some of you may remember the mention of DNA bases from the previous lesson when I taught you all about how DNA replicates. I never went further into what exactly bases are, and today I will do just that.
DNA is typically depicted as a latter structure that twists over itself — a double helix. However, DNA is actually two strands joined together by a hydrogen bond at the middle of each “prong” of the latter. These hydrogen bonds are resilient enough to hold DNA together, but weak enough to allow DNA to come apart for replication. Think of it as a latter being cut down the middle and joined at each step with glue. What essentially is each section of the latter and the half of the step beside it is a nucleotide.
Nucleotides are the monomer for DNA and RNA. Monomers are subunits that make up a polymer, which is the whole structure of the molecule. Nucleotides are consisted of a sugar, a phosphate, and a nitrogen base. We will be focusing on the nitrogen bases. DNA has four different types of these bases. There is adenine, thymine, guanine, and cytosine.
Bases always go with its respective pairing base. Adenine will connect to thymine, and guanine will connect to cytosine. Each half of a DNA strand will have a sequence of nucleotides that has its own base at the end, and when a half comes together with another half, the bases will join and be bonded together with the aforementioned hydrogen bonds.
An example of this is when one half-strand of DNA has a sequence of nucleotides with its own bases that follow as CGA TTA. The opposing half of the DNA strand will have its own sequence going as GCT AAT.
As for RNA, three of the bases in a standard strand of DNA are present in RNA, but instead of having thymine, RNA has uracil. Uracil will pair up with adenine for this type of nucleic acid. In the case of protein synthesis in which one of the first steps is a special type of RNA copying information from DNA, the adenine for DNA will transcribe to uracil for this type of RNA. Thymine for DNA will transcribe into adenine for the special RNA. As for guanine and cytosine in DNA, those will simply transcribe into cytosine and guanine respectively for the RNA, so nothing is different in that case.
We may now move onto DNA mutation. Mutation is described as the change of something, and it can often be found being used in a negative connotation. However, while DNA mutation can be detrimental for the organism, there are plenty of instances where the mutation does not effect the organism at all or it benefits them greatly. It really just depends on the kind of mutation one experiences.
There are several causes for a mutation in DNA, including inheriting such via genetics, prolonged exposure to ultraviolet light, radiation, or some chemicals. How exactly mutations occur can come in a multitude of ways.
The first is point mutation, or substitution. This is when the single nitrogen base of a DNA sequence is changed. This could be simulated by a sequence that follows as GAT, and through point mutation, the sequence now follows as GCT. Sometimes this type of mutation will happen, but nothing will ultimately change when the DNA has to play its part in protein synthesis, and this kind of substitution is called silent mutation.
The second type of mutation is frame shift mutation. This is when a nitrogen base is added, duplicated, or removed from a sequence. An addition of a base could be depicted as so: the sequence is CGA GTA; a base is added; the sequence is now CGA GTA C. As for the deletion of a base, it could be depicted as such: the sequence is CGA GTA; a base is removed; the sequence is now CGG TA. A duplication is similar to an addition, but instead of a random base being added, a previously existing base from the sequence is replicated. Frame shift mutation can also affect a plethora of bases, sometimes adding multiple bases into a sequence, taking away multiple bases from a sequence, or duplicating multiple bases from a sequence.
Something important to disclaim is that mutations can be confused with recombinant DNA. However, they are gravely different. As explained earlier, mutations occur when the organism is exposed to something or it is inherited from the parent. The end result of a mutation can be malignant, neutral, or beneficial. Recombinant DNA is when a strand of DNA from one organism is joined with a strand of DNA from another organism. This is done manually, and is typically done for salubrious purposes. While both affect the sequence of bases, they are completely unrelated. Besides, if we were to conflate the two, recombinant DNA would be more akin to an addition mutation, but either way, it is for the benefit of the organism, and is a procedure done by man.
Our second lesson has come to an end. Like I said in the lesson introduction, this lesson was brief. Some of you may like that, some of you may not — I don’t care.
Let logic disseminate.
