Protein is created through a long process that first starts at the DNA. The DNA is converted to mRNA through the use of the DNA polymerase, which copies a specific gene, replicating it, with the exception of replacing thymine with uracil. In eukaryotic cells, the strand of mRNA then gets modified and "spliced", removing the parts that aren't needed to create the proteins. The remaining strand of mRNA floats out from the cell nucleus and into the ribosomes. There, the ribosomes use tRNA, which grab free floating amino acids in the surrounding cytoplasm, to create a protein. Each tRNA and its corresponding amino acid matches with three nucleotide bases called a codon. Each codon represent the generation of one amino acid, eventually forming a chain of amino acids after the mRNA is done copying, which is folded into a protein in the rough endoplasmic reticulum.
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Visual Explanation of Protein Synthesis
All Image Credits goes to University High AP Biology Wiki |
The mutation that has the least effect is the substitution of a single base. These mutations are common. They usually get fixed by DNA repairing proteins before it actually becomes a problem. Especially if the mutated DNA that has been substituted at the end of a codon, this mutation may not have any effect, as multiple codons can equal the same amino acid. The greatest damaging mutation is, in my opinion, is either an insertion or a deletion at one of the nucleotides at the beginning of a gene. This causes the whole gene to be shifted, and, as a result, almost all the amino acids that are created after the amino acid created through the mutation are incorrect. Sometimes, this can also lead to a stop code early in the sequence, such that the protein production is cut short, and sometimes the deletion or addition of bases on the sequence to begin the gene could cause the gene to be started copying by the mRNA Polymerase much later in the gene or never at all. It matters where the mutation is if the mutation is an addition or a deletion. The nearer it is to the beginning of the gene sequence, the more damaging it can become. Otherwise, it doesn't really matter where the mutation is located.
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Example of a Point Mutation in the Form of Insertion
Image Credits to the YourGenome Project |
I chose the insertion mutation in step seven. I chose it, because it did a lot of damage if it was at the beginning of the sequence. In fact, it changed every single amino acid after the inserted gene was turned into an amino acid. It does comparatively more damage than substitution, but it can do about the same damage against deletion. Sometimes deletion is more effective, sometimes insertion is. It matters where the mutation occurs because the closer an insertion or deletion mutation is to the beginning of a gene, the more nucleotide bases it shifts and the more amino acids it changes.
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| Picture of my mutation I made in step 7 |
Mutations could change my DNA, changing the mRNA, changing the sequence of the amino acids, changing the protein, which change the phenotype, ultimately changing me! An example of a mutation is cystic fibrosis. CF is caused through an inheritable recessive allele (It is incompletely dominant). It is a mutation on the CFTR protein is on the codon 508, in which the U-U-U codon is deleted, removing phenylalanine from the sequence, causing the cells to be unable to create CFTR, leading to buildups of chlorine and mucus, which can lead to death.
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Visual location of the CF gene, along with the effects on the body's organs
Image Credit: Alila Medical Media/Shutterstock.com |
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