Question

Predict the amino acid sequence produced during translation by the following short hypothetical mRNA sequences (note that the second sequence was formed from the first by a deletion of only one nucleotide): Sequence 1: 5'-AUGCCGGAUUAUAGUUGA-3' Sequence \(2: 5^{\prime}-\) AUGCCGGAUUAAGUUGA-3' What type of mutation gave rise to Sequence 2 ?

Short answer

Question: Using the given mRNA sequences, predict the amino acid sequence produced during translation and identify the type of mutation responsible for the second sequence. mRNA Sequence 1: AUGCCGGAUUAUAGUUGA mRNA Sequence 2: AUGCCGGAUUAAGUUGA Answer: The amino acid sequence for Sequence 1 is Met-Pro-Asp-Tyr-Ser, and the amino acid sequence for Sequence 2 is Met-Pro-Asp. The mutation responsible for the second sequence is a frameshift deletion mutation.

Step-by-step solution

Decode mRNA Sequence 1 using a codon table

To predict the amino acid sequence from the mRNA, use the codon table to find the corresponding amino acid for every three base pairs in the sequence. The mRNA Sequence 1 is: AUGCCGGAUUAUAGUUGA.

Predict amino acid sequence for Sequence 1

Using the codon table, we translate the Sequence 1 as follows: AUG - Methionine (Met) CCG - Proline (Pro) GAU - Aspartic acid (Asp) UAU - Tyrosine (Tyr) AGU - Serine (Ser) UGA - Stop codon So, the amino acid sequence for Sequence 1 is: Met-Pro-Asp-Tyr-Ser.

Decode mRNA Sequence 2 using a codon table

Now we follow the same procedure for Sequence 2, which is: AUGCCGGAUUAAGUUGA.

Predict amino acid sequence for Sequence 2

Translate the Sequence 2 as follows: AUG - Methionine (Met) CCG - Proline (Pro) GAU - Aspartic acid (Asp) UAA - Stop codon The amino acid sequence for Sequence 2 is: Met-Pro-Asp.

Identify the mutation type

Looking at the original sequences, we can see that Sequence 2 was formed by deleting one nucleotide from Sequence 1. This deletion leads to a frameshift mutation since it changes the reading frame of the mRNA during translation, resulting in a different amino acid sequence and a premature stop codon. Therefore, the mutation that gave rise to Sequence 2 is a frameshift deletion mutation.

Key concepts

Understanding mRNA Translation

The cellular process of turning the genetic code into a string of amino acids, the building blocks of proteins, is known as mRNA translation. This crucial biological procedure takes place within the ribosomes, which can be thought of as the protein factories of the cell.

During translation, the sequence of bases in mRNA is read in groups of three, known as codons. Each codon specifies a particular amino acid. For instance, the codon AUG codes for Methionine, which interestingly, also serves as the start signal for translation. The process continues codon by codon until a stop codon is reached, which signals the end of protein synthesis.

The efficiency and accuracy of this process are vital, as even a small error can have significant consequences for the resulting protein, potentially leading to a variety of diseases or disorders.

Deciphering the Codon Table

The codon table is essentially a reference chart that biologists use to determine which amino acids correspond to which mRNA codons. It contains 64 entries, representing all possible combinations of three nucleotide bases (adenine (A), cytosine (C), guanine (G), and uracil (U) in mRNA).

This table is critical for translating mRNA sequences into amino acid sequences during protein synthesis. As seen in the exercise solution, we use the codon table to translate the sequence AUGCCGGAUUAUAGUUGA step by step into Methionine, Proline, Aspartic acid, Tyrosine, and Serine, followed by a stop codon. The table is a universal tool used in both research and education, highlighting the uniformity of the genetic code across organisms.

Sequencing Amino Acid Chains

An amino acid sequence is the order in which amino acids are linked together to form a protein. The sequence is determined by the mRNA's sequence of codons. As the ribosome reads the mRNA, it strings together amino acids in the precise order dictated by the codon sequence, like beads on a string.

The resulting chain folds into a specific three-dimensional structure critical for its function. Errors in the sequence, such as a misplaced or incorrect amino acid, can prevent the protein from functioning correctly. This highlights the importance of precision in the translation process. Our exercise illustrates what happens when the sequence is altered from Sequence 1 to Sequence 2, which affects the subsequent amino acid chain and ultimately the structure and function of the protein.

Exploring Genetic Mutations

A genetic mutation refers to any change in the DNA sequence that makes up a gene. Mutations can occur in various forms, such as substitutions, insertions, or deletions of nucleotides. A frameshift mutation, which is the focus of our exercise, is caused by the insertion or deletion of a number of nucleotides that is not a multiple of three.

Since codons are triplets, adding or removing a nucleotide changes the reading frame - hence, 'frameshift'. This often results in a completely different translation from the mutation site onward, creating a nonfunctional protein or terminating synthesis prematurely, as seen with Sequence 2 in our exercise. Understanding these mutations is imperative in genetics, as they can lead to diseases or genetic disorders and are also a driving force behind evolution.