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During DNA replication, a mistake occurs in which a single letter is replaced with a different one. This is called a substitution mutation, and it can occur in many types of cancer. Instead of the nitrogenous bases TAC, the DNA now codes for GAC.

Part 1: Identify the sequence of complementary mRNA nucleotides for the original DNA (TAC) and the mutated DNA (GAC).

Part 2: Use the codon table below to determine if this mutation in the DNA code will cause a change in the amino acid. Explain your reasoning.

[tex]\[
\begin{tabular}{|c|c|c|c|c|c|}
\hline
& \textbf{U} & \textbf{C} & \textbf{A} & \textbf{G} \\
\hline
\textbf{U} &
\begin{tabular}{l}
Phe \\
Phe \\
Leu \\
Leu
\end{tabular} &
\begin{tabular}{l}
Ser \\
Ser \\
Ser \\
Ser
\end{tabular} &
\begin{tabular}{l}
Tyr \\
Tyr \\
Stop \\
Stop
\end{tabular} &
\begin{tabular}{l}
Cys \\
Cys \\
Stop \\
Trp
\end{tabular} \\
\hline
\textbf{C} &
\begin{tabular}{l}
Leu \\
Leu \\
Leu \\
Leu
\end{tabular} &
\begin{tabular}{l}
Pro \\
Pro \\
Pro \\
Pro
\end{tabular} &
\begin{tabular}{l}
His \\
His \\
Gln \\
Gln
\end{tabular} &
\begin{tabular}{l}
Arg \\
Arg \\
Arg \\
Arg
\end{tabular} \\
\hline
\textbf{A} &
\begin{tabular}{l}
Ile \\
Ile \\
Ile \\
Met (Start)
\end{tabular} &
\begin{tabular}{l}
Thr \\
Thr \\
Thr \\
Thr
\end{tabular} &
\begin{tabular}{l}
Asn \\
Asn \\
Lys \\
Lys
\end{tabular} &
\begin{tabular}{l}
Ser \\
Ser \\
Arg \\
Arg
\end{tabular} \\
\hline
\textbf{G} &
\begin{tabular}{l}
Val \\
Val \\
Val \\
Val
\end{tabular} &
\begin{tabular}{l}
Ala \\
Ala \\
Ala \\
Ala
\end{tabular} &
\begin{tabular}{l}
Asp \\
Asp \\
Glu \\
Glu
\end{tabular} &
\begin{tabular}{l}
Gly \\
Gly \\
Gly \\
Gly
\end{tabular} \\
\hline
\end{tabular}
\][/tex]

Sagot :

GinnyAnsweridn
Sure, let's walk through this step-by-step.

### Part 1: Complementary mRNA Sequences
To find the complementary mRNA sequences for both the original and mutated DNA sequences, we need to know the base pairing rules for DNA to mRNA transcription:

- Adenine (A) in DNA pairs with Uracil (U) in mRNA.
- Thymine (T) in DNA pairs with Adenine (A) in mRNA.
- Cytosine (C) in DNA pairs with Guanine (G) in mRNA.
- Guanine (G) in DNA pairs with Cytosine (C) in mRNA.

Given the original DNA sequence: TAC
- T pairs with A
- A pairs with U
- C pairs with G

Thus, the complementary mRNA sequence for the original DNA (TAC) is: AUG

Given the mutated DNA sequence: GAC
- G pairs with C
- A pairs with U
- C pairs with G

Thus, the complementary mRNA sequence for the mutated DNA (GAC) is: CUG

### Part 2: Effect of Mutation on Amino Acid Sequence
We will use the codon table given to determine the amino acids coded by the mRNA sequences.

#### For the original mRNA sequence (AUG):
Looking at the codon table, the codon AUG corresponds to the amino acid Met(Start).

#### For the mutated mRNA sequence (CUG):
According to the codon table, the codon CUG corresponds to the amino acid Leu (Leucine).

### Conclusion
The original DNA sequence TAC transcribes to mRNA sequence AUG, which translates to the amino acid Met(Start).
The mutated DNA sequence GAC transcribes to mRNA sequence CUG, which translates to the amino acid Leu (Leucine).

Thus, the substitution mutation from TAC to GAC causes the resulting amino acid to change from Met(Start) to Leu. This change can potentially affect the protein being synthesized, which can have significant biological implications.
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