Chapter 8, Problem 12Q

(i)

Summary Introduction

To create:

The frame shift mutation from the DNA sequence: TAC CAG ATA CAC TCC CCT

Introduction:

The mutation which occurs in introns is insertion or deletion. It can cause shift in open reading frame of the gene sequence, and can change the amino acid sequence of the coded protein.

Explanation of Solution

Change in the genetic sequence of DNA, by addition and deletion of nucleotides, results in gene mutation.

Insertion mutation: This mutation occurs by insertion of one or more nucleotides in the DNA sequence. Insertion mutation is a type of frame shift mutation, as insertion of a single nucleotide shifts the whole reading frame in the DNA.

Original DNA sequence: $\underset{\_}{TAC}\underset{\_}{CAG}\underset{\_}{ATA}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}$

Frame shift due to insertion mutation: $\begin{array}{l}\underset{\_}{TAC}\underset{\_}{CCA}\underset{\_}{GAT}\underset{\_}{ACA}\underset{\_}{CTC}\underset{\_}{CCC}T\\ \uparrow \end{array}$

Deletion mutation: This mutation occurs due to removal of one or more nucleotides from DNA sequence. Deletion mutation is a type of frame shift mutation, as removal of a single nucleotide shifts the whole reading frame in the DNA.

Original DNA sequence: $\underset{\_}{TAC}\underset{\_}{CAG}\underset{\_}{ATA}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}$

Frame shift due to deletion mutation: $\begin{array}{l}\underset{\_}{TAC}\underset{\_}{CAG}\underset{\_}{A\xcancel{T}A}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}\\ \underset{\_}{TAC}\underset{\_}{CAG}\underset{\_}{AAC}\underset{\_}{ACT}\underset{\_}{CCC}CT\end{array}$

(ii)

Summary Introduction

To create:

The silent mutation from the DNA sequence: TAC CAG ATA CAC TCC CCT

Introduction:

The mutations in the codons that do not change the particular amino acid in the given polypeptide chain are called synonymous mutations. They are also called silent mutations because they cause no change in the structure of the protein.

Explanation of Solution

Silent mutation involves base substitution which results in same amino acids that was encoded by previous nucleotidal sequence.

Original DNA sequence: $\underset{\_}{TAC}\underset{\_}{CAG}\underset{\_}{ATA}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}$

Corresponding RNA sequence: $\underset{\_}{UAC}\underset{\_}{CAG}\underset{\_}{AUA}\underset{\_}{CAC}\underset{\_}{UCC}\underset{\_}{CCU}$

Amino acid sequence: Tyrosine Glutamine Methionine Histidine Serine Proline

Silent mutation: $\begin{array}{l}\underset{\_}{TAC}\underset{\_}{CAG}\underset{\_}{ATA}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}\\ \underset{\_}{TAT}\underset{\_}{CAG}\underset{\_}{ATA}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}\\ \uparrow \end{array}$

Corresponding RNA sequence: $\underset{\_}{UAU}\underset{\_}{CAA}\underset{\_}{AUG}\underset{\_}{CAU}\underset{\_}{UCU}\underset{\_}{CCC}$

Amino acid sequence: Tyrosine Glutamine Methionine Histidine Serine Proline

(iii)

Summary Introduction

To create:

The nonsense mutation from the DNA sequence: TAC CAG ATA CAC TCC CCT

Introduction:

The nonsense mutations are the mutations that generate the stop codon. The generated stop codon terminates the translational process and thus, the protein structure will not be formed because no more amino acids will be added to the sequence.

Explanation of Solution

Nonsense mutation involves substitution of a single base pair that yields a stop codon.

Original DNA sequence: $\underset{\_}{TAC}\underset{\_}{CAG}\underset{\_}{ATA}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}$

Nonsense mutation: $\begin{array}{l}\underset{\_}{TAG}\underset{\_}{CAG}\underset{\_}{ATA}\underset{\_}{CAC}\underset{\_}{TCC}\underset{\_}{CCT}\\ \uparrow \end{array}$

Corresponding RNA sequence: $\begin{array}{l}\underset{\_}{UAG}\underset{\_}{CAG}\underset{\_}{AUA}\underset{\_}{CAC}\underset{\_}{UCC}\underset{\_}{CCU}\\ \uparrow \\ \text{Stop}\text{codon}\end{array}$