Chapter 22, Problem 22.75P

Consider the following mRNA sequence: $\text{5}’\text{-CUU CAG CAC-3}’$.

1. What amino acid sequence is coded for by this mRNA?
2. What is the amino acid sequence if a mutation converts CAG to AAC?
3. What is the amino acid sequence if a mutation converts CUU to CUC?
4. What occurs when a mutation converts CAG to UAG?
5. What occurs if CU is deleted from the beginning of the chain?

Interpretation Introduction

(a)

Interpretation:

Peptide synthesized by the 5' CUU CAG CAC 3' mRNA should be identified.

Concept Introduction:

DNA and RNA transform genetic information of the living cells through triplet code, which is a sequence of three nucleotides on DNA or RNA molecules codes for a specific amino acid in protein synthesis.

Answer to Problem 22.75P

Peptide − Leu-Gln-His

Explanation of Solution

Codons are written from 5 prime end (5) to 3 prime end (3) of mRNA. There is a unique triplet representation for a particular amino acid. Below mentioned table represent the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

 

According to the above table; one amino acid has several triplets, but triplet code is unique for amino acid. CUU triplet is unique for Leucine. CAG triplet is unique for Glutamine. CAC is unique for Histidine.

Therefore, Leu-Gln-His is the amino acid sequence for 5' CUU CAG CAC 3'.

Interpretation Introduction

(b)

Interpretation:

Peptide formed from mutated mRNA5' CUU CAG AAC3' should be identified.

Concept Introduction:

DNA and RNA transform genetic information of the living cells through triplet code, which is a sequence of three nucleotides on DNA or RNA molecules codes for a specific amino acid in protein synthesis.

Mutation is an alteration of a sequence of nucleotides in DNA. Mutations can be classified based on the change that results in a DNA molecule.

Answer to Problem 22.75P

Peptide − Leu-Gln-Asn

Explanation of Solution

Mutation is an alteration of a sequence of nucleotides in DNA. When mutation happens at a particular position of a DNA molecule, that mutation goes through mRNA and translate a wrong peptide.

Mutations can be classified based on the change that results in a DNA molecule. There are three types of mutations which can be classified as follows;

1. Point mutations − A substitution of one nucleotide for another nucleotide.
2. Deletion mutations − One or more nucleotides is lost from a particular DNA molecule.
3. Insertion mutations − One or more nucleotides is added to a DNA molecule.

Codons are written from 5 prime end (5') to 3 prime end (3') of mRNA. There is a specific sequence of nucleotides for each amino acid. Below mentioned table represent the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

 

According to the above table; one amino acid has several triplets, but triplet code is unique for amino acid. CUU triplet is unique for Leucine. CAG triplet is unique for Glutamine. AAC is unique for Asparagine. There is a point mutation in the mRNA strand, which CAC in the normal strand converts to AAC in the mutated strand. The resulting protein is different from the un-mutated one.

Therefore, Leu-Gln-Asn is the amino acid sequence for 5' CUU CAG AAC 3'.

Interpretation Introduction

(c)

Interpretation:

Peptide formed from mutated mRNA 5' CUC CAG CAC 3' should be identified.

Concept Introduction:

DNA and RNA transform genetic information of the living cells through triplet code, which is a sequence of three nucleotides on DNA or RNA molecules codes for a specific amino acid in protein synthesis.

Mutation is an alteration of a sequence of nucleotides in DNA. Mutations can be classified based on the change that results in a DNA molecule.

Answer to Problem 22.75P

Peptide − Leu-Gln-His.

Explanation of Solution

Mutation is an alteration of a sequence of nucleotides in DNA. When mutation happens at a particular position of a DNA molecule, that mutation goes through mRNA and translate a wrong peptide.

Mutations can be classified based on the change that results in a DNA molecule. There are three types of mutations which can be classified as follows;

1. Point mutations − A substitution of one nucleotide for another nucleotide.
2. Deletion mutations − One or more nucleotides is lost from a particular DNA molecule.
3. Insertion mutations − One or more nucleotides is added to a DNA molecule.

Codons are written from 5 prime end (5') to 3 prime end (3') of mRNA. There is a specific sequence of nucleotides for each amino acid. Below mentioned table represent the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

 

According to the above table; one amino acid has several triplets, but triplet code is unique for amino acid. CUC triplet is unique for Leucine. CAG triplet is unique for Glutamine. CAC triplet is unique for Histidine. There is a point mutation in the mRNA strand, which CUU in the normal strand converts to CUC in the mutated strand. Though there is a point mutation in the strand, the resulting protein is not different from the un-mutated one.

Therefore, Leu-Gln-His is the amino acid sequence for 5' CUC CAG CAC 3'.

Interpretation Introduction

(d)

Interpretation:

Peptide formed from mutated mRNA 5' CUU UAG CAC 3' should be identified.

Concept Introduction:

DNA and RNA transform genetic information of the living cells through triplet code, which is a sequence of three nucleotides on DNA or RNA molecules codes for a specific amino acid in protein synthesis.

Mutation is an alteration of a sequence of nucleotides in DNA. Mutations can be classified based on the change that results in a DNA molecule.

Answer to Problem 22.75P

Amino acid is Leucine and after that amino acid sequence generation is terminated.

Explanation of Solution

Mutation is an alteration of a sequence of nucleotides in DNA. When mutation happens at a particular position of a DNA molecule, that mutation goes through mRNA and translate a wrong peptide.

Mutations can be classified based on the change that results in a DNA molecule. There are three types of mutations which can be classified as follows;

1. Point mutations − A substitution of one nucleotide for another nucleotide.
2. Deletion mutations − One or more nucleotides is lost from a particular DNA molecule.
3. Insertion mutations − One or more nucleotides is added to a DNA molecule.

Codons are written from 5 prime end (5') to 3 prime end (3') of mRNA. There is a specific sequence of nucleotides for each amino acid. Below mentioned table represent the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

 

According to the above table; one amino acid has several triplets, but triplet code is unique for amino acid. CUC triplet is unique for Leucine. UAG triplet is a unique for a stop codon. Hence, after this codon peptide synthesis is terminated. In this case required protein is not synthesized. Hence, the effect of this mutation may be catastrophic to the organism.

Therefore, Leu is the amino acid sequence for 5' CUU UAG CAC 3'

Interpretation Introduction

(e)

Interpretation:

Peptide formed from mutated mRNA 5' UCAGCAC 3' should be identified.

Concept Introduction:

DNA and RNA transform genetic information of the living cells through triplet code, which is a sequence of three nucleotides on DNA or RNA molecules codes for a specific amino acid in protein synthesis.

Mutation is an alteration of a sequence of nucleotides in DNA. Mutations can be classified based on the change that results in a DNA molecule.

Answer to Problem 22.75P

Peptide − Ser-Ala

Explanation of Solution

Mutation is an alteration of a sequence of nucleotides in DNA. When mutation happens at a particular position of a DNA molecule, that mutation goes through mRNA and translate a wrong peptide.

Mutations can be classified based on the change that results in a DNA molecule. There are three types of mutations which can be classified as follows;

1. Point mutations − A substitution of one nucleotide for another nucleotide.
2. Deletion mutations − One or more nucleotides is lost from a particular DNA molecule.
3. Insertion mutations − One or more nucleotides is added to a DNA molecule.

Codons are written from 5 prime end (5') to 3 prime end (3') of mRNA. There is a specific sequence of nucleotides for each amino acid. Below mentioned table represent the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

 

According to the above table; one amino acid has several triplets, but triplet code is unique for amino acid. Codons are written from 5 prime end (5') to 3 prime end (3') of mRNA and read as triplets, because of the deletion mutation which occurred here because of deletion of CU in the beginning of the mRNA, triplets are read as follows. UCA triplet is unique for Serine and GCA triplet is unique for Alanine. There is an additional A nucleotide, which is not involved into this peptide. Furthermore, this mutation generates totally different peptide and generated peptide is as follows; Ser-Ala is the amino acid sequence for 5' UCAGCAC 3'.