Problem 37 - Biology

Question

An adult with a history of tanning has his genome sequenced. The beginning of a protein-coding region of his DNA reads ATGGGGATATGGCAT. If the protein- coding region of a healthy adult reads ATGGGGATATGAGCAT, identify the site and type of mutation.

Step-by-Step Solution

Answer

The mutation is a point mutation (missense) at position 12.

Step 1: Compare the DNA Sequences

Identify the differences between the mutated DNA sequence (ATGGGGATATGGCAT) and the healthy DNA sequence (ATGGGGATATGAGCAT).

Step 2: Locate the Mutation Site

Find the position where the nucleotide differs between the two sequences. The difference is located at position 12.

Step 3: Determine the Type of Mutation

Classify the mutation based on the nucleotide change. Substituting G (Guanine) with A (Adenine) at position 12 is identified. This is a point mutation and more specifically, a missense mutation if it leads to a different amino acid.

Step 4: Confirm the Type of Mutation

In this case, the nucleotide change from G to A changes the codon, leading to a different amino acid in the protein sequence. Thus, it is a missense mutation.

Key Concepts

missense mutation

A missense mutation occurs when a single nucleotide change results in the substitution of a different amino acid in the protein being encoded. This can drastically affect protein function, depending on the roles of the changed amino acids. For example, if a nucleotide substitution results in changing a hydrophobic amino acid to a hydrophilic one, the protein may fold differently, potentially losing its function. In the given exercise, the substitution of guanine (G) with adenine (A) at a specific position causes a missense mutation, as it leads to a codon that codes for a different amino acid in the protein sequence.

point mutation

A point mutation is a type of genetic mutation where a single nucleotide base is changed, inserted, or deleted from a DNA or RNA sequence. Point mutations can be silent, missense, or nonsense mutations.

In the case of the provided exercise:

• A single nucleotide base change from G to A at position 12 occurs in the DNA sequence.
• This specific change results in a missense mutation because it alters the amino acid codon.

Point mutations can have a significant impact on protein function or be completely benign, depending on where they occur and the roles of the affected amino acids or genes.

nucleotide substitution

Nucleotide substitution is the replacement of one nucleotide base pair in a DNA sequence with another. There are two main types of nucleotide substitutions: transitions and transversions.

• Transitions involve substituting a purine for another purine (A ↔ G) or a pyrimidine for another pyrimidine (C ↔ T).
• Transversions involve substituting a purine for a pyrimidine or vice versa (A or G ↔ C or T).

In the exercise, the nucleotide substitution is a transition because guanine (a purine) is replaced by adenine (another purine). This substitution impacts the protein-coding sequence, leading to a missense mutation.

genetic sequence analysis

Genetic sequence analysis involves comparing DNA sequences to identify changes, which can help detect mutations. This process includes several steps:

• Obtaining and sequencing the DNA.
• Comparing the obtained sequence to a reference or healthy sequence.
• Identifying any differences in nucleotide positions.
• Classifying the types of mutations found.

In the given problem, genetic sequence analysis was used to:

• Identify the difference at position 12 of the DNA sequence.
• Classify the detected change as a point mutation.
• Further determine that this point mutation is a missense mutation due to its impact on the amino acid sequence.

This analysis is crucial in genetics research, diagnosis of genetic disorders, and understanding evolutionary relationships.