Chapter 22, Problem 22.135EP

Consider the following mRNA base sequence

$5\prime \text{CUU CAG}3\prime$

1. a. What dipeptide is coded for by this mRNA?
2. b. What dipeptide is formed if a point mutation converts CUU to CUC?
3. c. What dipeptide is formed if a point mutation converts CAG to AAG?
4. d. What dipeptide is formed if a point mutation converts CUU to CUC and CAG to AAG?

Interpretation Introduction

Interpretation: The dipeptide that is coded by the given mRNA has to be predicted.

Concept introduction: Ribonucleic acid (RNA) is responsible for the synthesis of the molecules that carry out essential cellular functions..  RNA contains the complementary base pairs.  The four complementary bases of RNA are adenine, uracil, guanine and cytosine.

A compound possessing two amino acids joined together by one peptide bond is known as dipeptide.  The amino acids present in the dipeptide are linked via peptide linkages.

Answer to Problem 22.135EP

The dipeptide that is coded by the given mRNA is $\text{Leu}-\text{Gln}$.

Explanation of Solution

The given mRNA base sequence is,

    $5\text{'}\text{CUU}\text{CAG}3\text{'}$

The amino acid that specifies the base pair, $\text{CUU}$ is leucine $\left(\text{Leu}\right)$.

The amino acid that specifies the base pair, $\text{CUU}$ is glutamine $\left(\text{Gln}\right)$.

Thus, the amino acid sequence or dipeptide for the given mRNA base sequence is $\text{Leu}-\text{Gln}$.

Interpretation Introduction

Interpretation: The dipeptide that is formed if a point mutation converts $\text{CUU}$ to $\text{CUC}$ has to be predicted.

Concept introduction: Ribonucleic acid (RNA) is responsible for the synthesis of the molecules that carry out essential cellular functions..  RNA contains the complementary base pairs.  The four complementary bases of RNA are adenine, uracil, guanine and cytosine.

The process of permanently changing the nucleotide sequence of a genome of any organism is known as mutation.  In point mutation, one base is replaced by another base in the given base pair sequence.

Answer to Problem 22.135EP

The dipeptide that is formed if a point mutation converts $\text{CUU}$ to $\text{CUC}$ is $\text{Leu}-\text{Gln}$.

Explanation of Solution

The given mRNA base sequence is,

    $5\text{'}\text{CUU}\text{CAG}3\text{'}$

If point mutation occurs in the given mRNA base sequence and converts $\text{CUU}$ to $\text{CUC}$ then the base sequence becomes,

    $5\text{'}\text{CUC}\text{CAG}3\text{'}$

The amino acid that specifies the base pair, $\text{CUC}$ is leucine $\left(\text{Leu}\right)$.

The amino acid that specifies the base pair, $\text{CUU}$ is glutamine $\left(\text{Gln}\right)$.

Thus, the amino acid sequence or dipeptide formed after the point mutation is $\text{Leu}-\text{Gln}$ because both $\text{CUC}$ and $\text{CUU}$ are coded by leucine only.

Interpretation Introduction

Interpretation: The dipeptide that is formed if a point mutation converts $\text{CAG}$ to $\text{AAG}$ has to be predicted.

Concept introduction: Ribonucleic acid (RNA) is responsible for the synthesis of the molecules that carry out essential cellular functions..  RNA contains the complementary base pairs.  The four complementary bases of RNA are adenine, uracil, guanine and cytosine.

The process of permanently changing the nucleotide sequence of a genome of any organism is known as mutation.  In point mutation, one base is replaced by another base in the given base pair sequence.

Answer to Problem 22.135EP

The dipeptide that is formed if a point mutation converts $\text{CAG}$ to $\text{AAG}$ is $\text{Leu}-\text{Lys}$.

Explanation of Solution

The given mRNA base sequence is,

    $5\text{'}\text{CUU}\text{CAG}3\text{'}$

If point mutation occurs in the given mRNA base sequence and converts $\text{CAG}$ to $\text{AAG}$ then the base sequence becomes,

    $5\text{'}\text{CUC}\text{AAG}3\text{'}$

The amino acid that specifies the base pair, $\text{CUC}$ is leucine $\left(\text{Leu}\right)$.

The amino acid that specifies the base pair, $\text{AAG}$ is Lysine $\left(\text{Lys}\right)$.

Thus, the amino acid sequence or dipeptide formed after the point mutation is $\text{Leu}-\text{Lys}$.

Interpretation Introduction

Interpretation: The dipeptide that is formed if a point mutation converts $\text{CUU}$ to $\text{CUC}$ and $\text{CAG}$ to $\text{AAG}$ has to be predicted.

Concept introduction: Ribonucleic acid (RNA) is responsible for the synthesis of the molecules that carry out essential cellular functions..  RNA contains the complementary base pairs.  The four complementary bases of RNA are adenine, uracil, guanine and cytosine.

The process of permanently changing the nucleotide sequence of a genome of any organism is known as mutation.  In point mutation, one base is replaced by another base in the given base pair sequence.

Answer to Problem 22.135EP

The dipeptide that is formed if a point mutation converts $\text{CUU}$ to $\text{CUC}$ and $\text{CAG}$ to $\text{AAG}$ is $\text{Leu}-\text{Lys}$.

Explanation of Solution

The given mRNA base sequence is,

    $5\text{'}\text{CUU}\text{CAG}3\text{'}$

If point mutation occurs in the given mRNA base sequence and converts $\text{CUU}$ to $\text{CUC}$ and $\text{CAG}$ to $\text{AAG}$ then the base sequence becomes,

    $5\text{'}\text{CUU}\text{AAG}3\text{'}$

The amino acid that specifies the base pair, $\text{CUU}$ is leucine $\left(\text{Leu}\right)$.

The amino acid that specifies the base pair, $\text{AAG}$ is Lysine $\left(\text{Lys}\right)$.

Thus, the amino acid sequence or dipeptide formed after the point mutation is $\text{Leu}-\text{Lys}$ because both $\text{CUC}$ and $\text{CUU}$ are coded by leucine only.