Chapter 18.1, Problem 20AQP

a.

Summary Introduction

To determine:

Mutation 1: A transition at nucleotide 11 in a given nucleotide sequence of ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$

Explanation of Solution

Transition mutation is a type of base-substitution mutation in which either a purine base is replaced with different purine base or pyrimidine base is replaced with different pyrimidine base. Due to transition mutation at nucleotide 11, the DNA template formed is ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{T}C\text{A}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$ in which thymine is replaced by cytosine. The $\text{m-RNA}$ form ${\text{5}}^{\prime }\text{-AUG}\text{ACC}\text{GGC}AGU\text{CAA}\text{CUA}\text{UAU}\text{UGA-}{\text{3}}^{\prime }$ and codon formed after mutation are AGU which codes for amino acid serine.

b.

Summary Introduction

To determine:

Mutation 2: A transition at nucleotide 13 in a given nucleotide sequence of ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$

Explanation of Solution

In transition mutation, a purine base is replaced by different purine base and pyrimidine base is replaced by different pyrimidine base. The transition at 13 nucleotides of DNA sequence results ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}A\text{TT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$ in which guanine is replaced by adenine. The $\text{m-RNA}$ formed is ${\text{5}}^{\prime }\text{-AUG}\text{ACC}\text{GGC}\text{AGU}U\text{AA}\text{CUA}\text{UAU}\text{UGA-}{\text{3}}^{\prime }$ and codon UAA acts as stop codon that terminates the process of translation.

c.

Summary Introduction

To determine:

Mutation 3: A one-nucleotide deletion at nucleotide 7 in a given nucleotide sequence of ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$.

Explanation of Solution

In deletion mutation, removal of single nucleotide results in a frameshift mutation that changes the reading frame. After deletion of the nucleotide at 7 positions the DNA sequence formed is ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CGT}\text{TAG}\text{TTG}\text{ATA}\text{TAA}\text{CT-}{\text{5}}^{\prime }$ in which deletion of cytosine occurs. The $\text{m-RNA}$ formed is ${\text{5}}^{\prime }\text{-}\text{AUG}\text{ACC}GCA\text{AUC}\text{AAC}\text{UAU}\text{AUU}\text{GA-}{\text{3}}^{\prime }$. The codon GCA after deletion codes for alanine.

d.

Summary Introduction

To determine:

Mutation 4: A $\text{T}\to \text{A}$ transversion at nucleotide 15 in a given nucleotide sequence of ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$.

Explanation of Solution

In transversion mutation a pyrimidine base is replaced with purine base or purine base is replaced with pyrimidine base. After transversion of $\text{T}\to \text{A}$ the DNA sequence formed is ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}\text{GT}A\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$. The $\text{m-RNA}$ formed is ${\text{5}}^{\prime }\text{-AUG}\text{ACC}\text{GGC}\text{AGU}CAU\text{CUA}\text{UAU}\text{UGA-}{\text{3}}^{\prime }$ and codon CAU codes for amino acid histidine.

e.

Summary Introduction

To determine:

Mutation 5: An addition of TGG after nucleotide 6 in a given nucleotide sequence of ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$.

Explanation of Solution

Addition of nucleotide in a DNA sequence results in a change in codon sequence that codes for different protein. On addition of TCG after 6 nucleotide DNA sequence is ${\text{3}}^{\prime }\text{-TAC}\text{TGG}TCG\text{CCG}\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$. So the $\text{m-RNA}$ formed is ${\text{5}}^{\prime }\text{-AUG}\text{ACG}ACC\text{GGC}\text{AAU}\text{CAA}\text{CUA}\text{UAU}\text{UGA-}{\text{3}}^{\prime }$  and codon ACC codes for amino acid threonine.

f.

Summary Introduction

To determine:

Mutation 6: A transition at nucleotide 9  in a given nucleotide sequence of ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CCG}\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$.

Explanation of Solution

Transition mutation involves the replacement of a purine with purine or pyrimidine with a pyrimidine. In this transition at nucleotide 9 forms, the DNA sequence is ${\text{3}}^{\prime }\text{-TAC}\text{TGG}\text{CC}A\text{TTA}\text{GTT}\text{GAT}\text{ATA}\text{ACT-}{\text{5}}^{\prime }$ in which guanine is replaced by adenine. So, the $\text{m-RNA}$ formed is ${\text{5}}^{\prime }\text{-AUG}\text{ACG}GGU\text{AAU}\text{CAA}\text{CUA}\text{UAU}\text{UGA-}{\text{3}}^{\prime }$ and codon GGU codes for amino acid glycine.

Conclusion

The mutation causes the change of sequence of nucleotide (one base) in a gene or a chromosome. A change in nucleotide at 11 position results in the coding of amino acid serine. Mutation at nucleotide 13 results in a stop codon. Deletion of the nucleotide at 7 results in the coding of alanine. Transversion of $\text{T}\to \text{A}$ results in the coding of amino acid histidine. Addition of TGG after six nucleotide results in the coding of amino acid threonine and transition at nucleotide 9 results in the coding of glycine amino acid.