15 Aug, 2024
· Biology

A single nucleotide deletion during DNA replication:

  • Causes one amino acid of the protein to be incorrect
  • Causes all of the amino acids of the protein to be incorrect
  • Causes the amino acids encoded by nucleotides after the deletion to be incorrect
  • Causes the amino acids encoded by nucleotides before the deletion to be incorrect
  • Has no effect on the resulting protein
Short Answer
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Long Explanation

Explanation

A single nucleotide deletion can have a profound impact on the protein that is ultimately produced. This type of mutation leads to a frameshift mutation, where the reading frame of the mRNA is altered. The reading frame is critical for correctly translating the nucleotide sequence into a sequence of amino acids. When a nucleotide is deleted, it shifts the grouping of codons downstream of the deletion site, resulting in the incorporation of incorrect amino acids.

Frameshift Mutation Impact

The general formula for a frameshift mutation resulting from a single nucleotide deletion is:

Mutated sequence=\text{Mutated sequence} = =Original sequence∖Deleted Nucleotide= \text{Original sequence} \setminus \text{Deleted Nucleotide}

Where:

Codon={(n, n+1, n+2),if no mutation(n-1, n, n+1),if single deletion\text{Codon} = \begin{cases} \text{(n, n+1, n+2)}, & \text{if no mutation} \\ \text{(n-1, n, n+1)}, & \text{if single deletion} \end{cases}

Because the codons are read in groups of three, any deletion shifts the reading frame, causing all subsequent amino acids to be incorrect. This frameshift often results in a completely nonfunctional protein, as the altered amino acid sequence will most likely lead to early termination or misfolded protein structures.

Example

Consider a hypothetical mRNA sequence:

Original mRNA=AUG-CGG-GUU-AAA\text{Original mRNA} = \text{AUG-CGG-GUU-AAA}

A single nucleotide deletion might result in:

Deleted form=AUG-CGR-GUU-AAA\text{Deleted form} = \text{AUG-CGR-GUU-AAA}

Where 'CGR' constitutes a misshaped codon, potentially leading to nonfunctional outcomes.

Conclusion

The most significant impact of a single nucleotide deletion is that it causes the amino acids encoded by nucleotides after the deletion to be incorrect**. This frameshift mutation affects protein function and can lead to severe consequences in biological systems.

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Rebecca Green

Biology and Health Content Writer at Math AI

Rebecca Green, who recently completed her Master's in Biology from the University of Cape Town, works as a university lab teaching assistant and a part-time contract writer. She enjoys making biology fun and accessible through engaging content.

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Concept

Frameshift Mutation

Definition

A frameshift mutation occurs when there is an insertion or deletion of a nucleotide base in the DNA sequence that is not in multiples of three. This alters the reading frame of the genetic code, ultimately changing the way the sequence is read during translation.

Understanding the Reading Frame

In molecular biology, the reading frame is a way of dividing the sequence of nucleotides in DNA or RNA into a set of consecutive, non-overlapping triplets or codons. Each codon corresponds to a specific amino acid or a stop signal during protein synthesis.

How it Affects Protein Synthesis

When the reading frame changes, every codon downstream from the mutation is affected, leading to incorrect amino acids being incorporated into the protein. This usually results in a nonfunctional protein or a protein with an entirely different function.

Example

Consider a sequence of DNA with its corresponding codons:

Original DNA Sequence:\text{Original DNA Sequence:} ATG GGA CTA CGT\text{ATG GGA CTA CGT} Codons:\text{Codons:} AUG GGA CUA CGU\text{AUG GGA CUA CGU} Amino Acids:\text{Amino Acids:} Met Gly Leu Arg\text{Met Gly Leu Arg}

If there is a deletion of one nucleotide (e.g., the second 'G'):

Altered DNA Sequence:\text{Altered DNA Sequence:} ATG G A C TA CGT\text{ATG G A C TA CGT} Altered Codons:\text{Altered Codons:} AUG GAC UAC GU\text{AUG GAC UAC GU} Altered Amino Acids:\text{Altered Amino Acids:} Met Asp Tyr ... \text{Met Asp Tyr ... }

Impact on Function

  • Nonfunctional proteins: Many frameshift mutations lead to the production of truncated proteins due to the presence of premature stop codons.
  • Diseases: Frameshift mutations are known to cause various genetic disorders, such as cystic fibrosis and Tay-Sachs disease.

Understanding frameshift mutations is crucial for genetic research, disease diagnosis, and treatment development.

Concept

Reading Frame

Reading Frame in Genetics

A reading frame is a way of dividing the sequence of nucleotides in a DNA or RNA molecule into a set of consecutive, non-overlapping triplets, or codons. Each of these codons encodes for a specific amino acid, or a stop signal during the process of translation.

How Reading Frames Work

Given a sequence of nucleotides, there are three possible reading frames within a single strand of DNA or RNA. This is because a codon consists of three nucleotides, and so the sequence can be read in three different ways depending on where you start:

  1. First Reading Frame: Begins at the first nucleotide.
  2. Second Reading Frame: Begins at the second nucleotide.
  3. Third Reading Frame: Begins at the third nucleotide.

For example, for the sequence AGCTAGC, the three reading frames would be:

  • AGC TAG C...
  • GCT AGC ...
  • CTA GCT ...

Importance of the Correct Reading Frame

Ensuring that the correct reading frame is used is critical for the synthesis of functional proteins. If the reading frame is shifted, a phenomenon known as a frameshift mutation occurs, which can lead to the production of nonfunctional proteins.

Mathematical Representation

A sequence of nucleotides can be represented as:

Nucleotide Sequence={N1,N2,N3,…,Ni}\text{Nucleotide Sequence} = \{N_1, N_2, N_3, \ldots, N_i\}

Where NiN_i represents each nucleotide. The three possible reading frames can be depicted as:

Frame 1:(N1,N2,N3),(N4,N5,N6),…Frame 2:(N2,N3,N4),(N5,N6,N7),…Frame 3:(N3,N4,N5),(N6,N7,N8),…\begin{aligned} &\text{Frame 1:} & (N_1, N_2, N_3), (N_4, N_5, N_6), \ldots \\ &\text{Frame 2:} & (N_2, N_3, N_4), (N_5, N_6, N_7), \ldots \\ &\text{Frame 3:} & (N_3, N_4, N_5), (N_6, N_7, N_8), \ldots \\ \end{aligned}

Example

Consider the mRNA sequence AUGGUCACG:

  1. First Reading Frame: AUG-GUC-ACG
  2. Second Reading Frame: A-UGG-UCA-CG
  3. Third Reading Frame: AU-GGU-CAC-G

Translation and Stop Codons

During protein synthesis, the ribosome reads the mRNA in sets of three nucleotide bases (codons) and translates each codon into one amino acid. The process starts at a start codon (usually AUG) and terminates at a stop codon (such as UAA, UAG, or UGA).

Maintaining the correct reading frame ensures that the resultant protein will have the correct sequence of amino acids, thereby preserving its structure and function.