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Does the last nucleotide in a codon have less specificity than the others and if so why?
Wiki User
∙ 14y ago
Yes, this is true (generally speaking). In many cases there are two different codons that differ at the third position yet code the same amino acid.
I hypothesize that the reason that this is so is that nature has naturally selected the codons to be resistant to certain transition and transversion mutations.
transition mutation = purine to purine or pyrimidine to pyrimidine
transversion mutation = purine to pyrimidine or pyrimidine to purine
Wiki User
∙ 14y ago
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What kind of mutation is this ugu-ccg-GAA-cga to ugc-cgg-GAA-cga?
The sequence TGA-GCC-ATG-A is changed in 2 places to become TGA-GCA-CAT-GA.When one base is changed, it is called a point mutation.In this case, a GCC in the DNA has been changed to a GCA. This would mean the mRNA codon (coded for by this DNA) would change from CGG to CGU.Both of these codons code for the same amino acid - Arginine. Therefore this type of point mutation is known as a silent mutation.The extra C that appears would be called an addition mutation, which is a type of frameshift mutation.
Why is UAG codon called amber codon?
The term "amber" was first used in studies on bacteriophage T4 by researchers in the 1960s, where the UAG codon was found to cause premature termination of protein synthesis. The researchers chose to name it "amber" after the first mutant strain in which the codon was discovered.
In the polymerization of DNA a phosphodiester bond is formed between a phosphate group of the nucleotide being added and what of the nucleotide in the polymer?
The phosphate group of the incoming nucleotide joins the 3'-hydroxyl group of the last nucleotide in the growing DNA chain to form a phosphodiester bond.
What is the final step in the natural process for making proteins?
The last step is reading the termination codon which will release the protein.
If an mRNA is made up of 60 bases how many codons does it contain and how many amino acid does it code for?
A codon is exactly three bases long, so an mRNA strand with 60 bases would contain 20 codons. The first codon will encode for methionine (this is called the "start" codon) and the last codon will be a "stop" codon, which does not encode for an amino acid. Thus, an mRNA strand of 60 bases will code for 19 amino acids. Keep in mind, it is possible for a stop codon to be anywhere on the mRNA strand, and when a stop codon reaches the ribosome, translation must stop. For example, if an mRNA strand contained 30 codons, and the 15th were a stop codon, the mRNA would only code for 14 amino acids and then be done. The other 15 codons would go untranslated.
What meaning do the first and last codons have for protein synthesis?
The start codon (AUG) signifies the beginning of protein synthesis and codes for the amino acid methionine. The stop codons (UAA, UAG, UGA) signal the end of protein synthesis and do not code for any amino acid.
Which mRNA codons will start the process of translation?
If you're referring to stop codons, then there are three: UAA, UAG and UGA. They do indeed stop translation, though I wouldn't say they halt ribosomes. Stop codons code for a releaser enzyme, one that fits the A site of the ribosome, but does not carry an amino acid. This enzyme cuts the bond between the polypeptide and the last tRNA.
How many codons are present on the mRNA strand?
The number of codons on an mRNA strand depends on the length of the mRNA molecule. Each codon is made up of three nucleotide bases, so to determine the number of codons, you would need to know the total number of nucleotide bases on the mRNA strand and divide that number by 3.
Does last mean come before all others?
No, "Last" means come after all others. "First" means come before all others.
What would happen if the very last stop codon of a mRNA molecule was mutated into a regular codon?
If the last stop codon of an mRNA molecule is mutated into a regular codon, translation would continue beyond the normal termination point. This could result in the synthesis of a longer protein or a completely nonfunctional protein, depending on where translation ultimately terminates.
What is the maximum number of amino acids that could be coded for by a sextion of mrna with the sequence guucagaacugu?
The maximum number of amino acids that could be coded for by a section of mRNA is determined by the reading frame. For the mRNA sequence "guucagaacugu," if we assume a start codon (AUG) at the beginning and use the genetic code to translate each codon to an amino acid, we can identify the potential amino acids until a stop codon is reached. In this case, the sequence could potentially code for at most three amino acids before a stop codon is encountered.
