How can a single letter change in a DNA sequence could lead to a different protein?

Answer 1

Every single genes has multiple functions to perform. This is very complex phenomena, probably. Contributor tried to explain the same, but probably failed in that attempt. Interaction and discussion is needed for the same probably.

Answer 2

A small change (mutation) in the DNA of a single gene can have negligible to debilitating effects on the protein product from that gene. Small mutations include point mutations, insertions and deletions. Point mutation can be silent (the mutation does not affect the amino acid sequence due to redundancies in the genetic code, e.g. CUG and CUA both code for leucine), synonymous (the mutation changes a single amino acid but the new amino acid is of the same category as the original amino acid, e.g. leucine -> valine, both hydrophobic), non-synonymous (the mutation changes a single amino acid but the amino acid is of a different category as the original amino acid, e.g. leucine (hydrophobic) -> aspartic acid (acidic)), or non-sensical (the mutation changes a single amino acid but the new codon is a stop codon rather than another amino acid, e.g. Tyrosin (UAC) -> STOP (UAA)). Of these point mutations, a non-sense mutation is the most serious since a stop codon result in a large chunk of the gene not being translated and therefore a truncated protein. The insertion and deletion mutations are even more serious. These mutations insert or delete a base from DNA, resulting in frameshift mutations. Frameshift mutations occur since DNA is always read in 3-letter codons and the insertion or deletion of a single base will shift the downstream sequence down or up by a base, resulting in complete jargon for the rest of the gene. For example: THE CAT ATE THE FAT RAT An insertion would be: THE ACA TAT ETH EFA TRA T A deletion would be: THE CAA TET HEF ATR AT

Answer 3

Because a different amino acid is produced and that amino acid could have very different properties. Say a hydrophobic amino acid was replaced with a hydrophillic amino acid. The tertiary folding of the protein at that point would be exactly opposite in nature, thus a different protein.

Answer 4

A mutation in the DNA results in a change in the mRNA and, ultimately, to a different protein structure.

Mutations in DNA cause incorrect amino acids to be inserted into the protein. The sequence of amino acids and the interactions between them determine the shape of the protein. Finally, the shape of the protein determines the function of it. Proteins with different sequences, shapes and functions are different proteins.

Every 3 nucleotides in the DNA sequence is called a "codon". We could also consider each "codon" to be like a word. We could also consider a gene in the DNA sequence to be like a sentence. A few of the "codons," instead of being read like words instead end the gene like a period ends a sentence. When a gene gets transcribed from DNA to mRNA then attaches to a ribosome it gets translated to a protein.

Now to use our gene-sentence and codon-word analogy and treating the transcription and translation process that makes protein as analogous to reading a sentence out loud, we can see how a mutation changes a protein.

If we consider the sentence below as a gene and the words as codons, read it out loud:

This is the original wording.

Now if we make a single letter mutation, read it out loud:

This is the original warding.

Now if we make a different single letter mutation, read it out loud:

This is the origznal wording.

Now if we make a single letter mutation that converts the word/codon to a period ".", read it out loud:

This is .

The first mutation might still make a working protein, the second mutation makes a defective (nonsense) protein, the third mutation makes a very short and totally useless protein.

Answer 5

A frameshift mutation is a type of mutation involving the insertion or deletion of a nucleotide in which the number of deleted base pairs is not divisible by three. "Divisible by three" is important because the cell reads a gene in groups of three bases. Each group of three bases corresponds to one of 20 different amino acids used to build a protein. If a mutation disrupts this reading frame, then the entire DNA sequence following the mutation will be read incorrectly.
If a mutation disrupts this reading frame, then the entire DNA sequence following the mutation will be read incorrectly.

Here is an example of one sentence with words of only three letters: The big red pig ate the red rag. Each word will make one amino acid and the words make a sentence that makes sense.
Mutations that replaces one base for another will result in this: The big res dpi gat eth ere dra g.

Answer 6

A single letter change in a DNA sequence, known as a point mutation, can lead to a different protein if it results in a different amino acid being incorporated into the protein sequence. This change can alter the protein's structure and function, impacting its efficiency or ability to carry out its normal role in the cell.

Answer 7

A mutation in the DNA could cause a change in the amino acid sequence, which could cause a change in the structure of the protein, which could cause it to function poorly or not at all.