BY Chelsea SunWhen Covid-19 first emerged in the world, there was talk of 2 distinct variants -- one that would only cause minor to none symptoms in the host and another that would cause more severe, and even deadly symptoms. But now a year after the novel Coronavirus first took the world by storm, many more variants of Covid-19 have appeared. What Causes Variations in Covid-19? The different variants of Covid-19 are caused by mutations (or errors) in the replication of the virus’s genetic material. While normal cells and DNA viruses can catch and correct replication errors, RNA viruses cannot. Thus RNA viruses (such as Covid-19 and Influenza) are more prone to replication errors and mutations. Luckily, Covid-19 does not mutate that quickly, mutating at least 4 times more slowly than Influenza. So what type of mistakes are there in the replication of genetic material? First, we need to understand how proteins are created from RNA. A quick and simple explanation is that RNA is a long strand of alternating letters U, C, A, and G. These “letters” represent the nucleotides that make up the RNA, uracil (U), cytosine (C), adenine (A), and guanine (G). These “letters” are grouped into 3s called codons, and each codon corresponds with a specific amino acid (see graph below). The order these amino acids appear in is their specific position in the protein. The protein is finished when a specific codon (UAA, UAG, or UGA) signals a stop in the replication process. In the case of Covid-19, it is this protein that was created using the virus’s RNA that attacks the body. Now that we have a basic understanding of how proteins are created, we can talk about the different types of mistakes in the replication process. There are 3 main types of base substitutions, deletions, and insertion. Base substitution is when a “letter” is mistakenly replaced with another nucleotide in the genetic code. A deletion mutation is when a “letter” or nucleotide is mistakenly skipped over, or deleted, and an insertion mutation is when a nucleotide is accidentally added. Sometimes these mutations will cause no changes to the protein, as multiple codons do correspond with the same amino acid. However, other times we are not as lucky, and amino acids different than what was coded in the genetic material are added, changing the protein entirely. Some mutations in Covid-19 had no impact, some negatively impacted the viral protein, and others gave the virus an advantage. New Covid-19 Variants Recently, there has been talk about the new mutations found in the United Kingdom and South Africa-- both are variants where the mutation has benefited the virus, allowing them to spread more easily. The B.1.1.7 variant of Covid-19 was discovered around September 2020 in the UK. This Covid-19 variant is characterized by the replacement of amino acid asparagine (Asn) with tyrosine (Tyr) at position 501. Some versions of this variant also include the deletion of 6 nucleotides, resulting in the deletion of the 2 amino acids that were in positions 69 and 70. Some versions also include a change of Proline to Histidine at position 681. As a result of the B.1.1.7 mutations, the receptor-binding domain of a spike protein was changed. And it is the spike proteins that allow viruses to attach to cells and inject their genetic material. Consequently, the B.1.1.7 Covid variant is more prone to being spread between hosts, it also spreads more quickly within the host. There have been some studies that have concluded that this strand is also more deadly, but more research needs to be done. Luckily, the vaccines that have been created seem to not be affected by the B.1.1.7 variant. On the other hand, the vaccines are slightly less effective on the B.1.351 Coronavirus variant which was first identified in South Africa around October 2020. The three mutations that characterize this version of Covid-19 include the change of Lysine to Asparagine at position 417, Glutamic acid to Lysine at position 484, and Asparagine to Tyrosine at position 501. Unlike the B.1.1.7 strand, this strand does not contain the deletion of amino acids at positions 69 and 70. However, similar to the B.1.1.7 strand, the mutations in B.1.351 also affect the spike proteins on the Covid-19 virus. References:
0 Comments
Leave a Reply. |
ABOUTSubmit your work to be considered for publication in the Newly Created SNHS Newspaper! CategoriesOuter Space History Biology
|