Chapter 22, Problem 61P

Write a possible mRNA sequence that codes for each peptide.

1. lle-Met-Lys-Ser-Tyr
2. Pro-Gln-Glu-Asp-Phe
3. Thr-Ser-Asn-Arg

Interpretation Introduction

(a)

Interpretation:

Possible mRNA sequence that codes for Ile-Met-Lys-Ser-Tyr should be identified.

Concept Introduction:

Genetic code − 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 61P

5' AUU-AUG-AAA-UCU-UAU 3'

Explanation of Solution

Codons are written from 5 prime ends (5') to 3 prime ends (3') of mRNA. There is a specific sequence of nucleotides for each amino acid. The below-mentioned table represents the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

First Base (5' end)	Second Base								Third Base (3' end)
	U		C		A		G
U	UUU	Phe	UCU	Ser	UAU	Tyr	UGU	Cys	U
	UUC	Phe	UCC	Ser	UAC	Tyr	UGC	Cys	C
	UUA	Leu	UCA	Ser	UAA	Stop	UGA	Stop	A
	UUG	Leu	UCG	Ser	UAG	Stop	UGG	Trp	G
C	CUU	Leu	CCU	Pro	CAU	His	CGU	Arg	U
	CUC	Leu	CCC	Pro	CAC	His	CGC	Arg	C
	CUA	Leu	CCA	Pro	CAA	Gln	CGA	Arg	A
	CUG	Leu	CCG	Pro	CAG	Gln	CGG	Arg	G
A	AUU	Ile	ACU	Thr	AAU	Asn	AGU	Ser	U
	AUC	Ile	ACC	Thr	AAC	Asn	AGC	Ser	C
	AUA	Ile	ACA	Thr	AAA	Lys	AGA	Arg	A
	AUG	Met	ACG	Thr	AAG	Lys	AGG	Arg	G
G	GUU	Val	GCU	Ala	GAU	Asp	GGU	Gly	U
	GUC	Val	GCC	Ala	GAC	Asp	GGC	Gly	C
	GUA	Val	GCA	Ala	GAA	Glu	GGA	Gly	A
	GUG	Val	GCG	Ala	GAG	Glu	GGG	Gly	G

According to the above table; one amino acid has several triplets, but triplet code is unique for an amino acid. For Isoleucine amino acid (Ile) there are 3 different but unique codons are there, which are AUU, AUC and AUA. Likewise, for each amino acid, there are several triplets. Therefore, for a particular amino acid sequence there can be different triplet codes.

5' AUU-AUG-AAA-UCU-UAU 3' is a one possible mRNA sequence for Ile-Met-Lys-Ser-Tyr sequence.

Interpretation Introduction

(b)

Interpretation:

Possible mRNA sequence that codes for Pro-Gln-Glu-Asp-Phe should be identified.

Concept Introduction:

Genetic code − 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 61P

5' CCU-CAA-GAA-GAU-UUU 3'

Explanation of Solution

Codons are written from 5 prime ends (5') to 3 prime ends (3') of mRNA. There is a specific sequence of nucleotides for each amino acid. The below-mentioned table represents the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

First Base (5' end)	Second Base								Third Base (3' end)
	U		C		A		G
U	UUU	Phe	UCU	Ser	UAU	Tyr	UGU	Cys	U
	UUC	Phe	UCC	Ser	UAC	Tyr	UGC	Cys	C
	UUA	Leu	UCA	Ser	UAA	Stop	UGA	Stop	A
	UUG	Leu	UCG	Ser	UAG	Stop	UGG	Trp	G
C	CUU	Leu	CCU	Pro	CAU	His	CGU	Arg	U
	CUC	Leu	CCC	Pro	CAC	His	CGC	Arg	C
	CUA	Leu	CCA	Pro	CAA	Gln	CGA	Arg	A
	CUG	Leu	CCG	Pro	CAG	Gln	CGG	Arg	G
A	AUU	Ile	ACU	Thr	AAU	Asn	AGU	Ser	U
	AUC	Ile	ACC	Thr	AAC	Asn	AGC	Ser	C
	AUA	Ile	ACA	Thr	AAA	Lys	AGA	Arg	A
	AUG	Met	ACG	Thr	AAG	Lys	AGG	Arg	G
G	GUU	Val	GCU	Ala	GAU	Asp	GGU	Gly	U
	GUC	Val	GCC	Ala	GAC	Asp	GGC	Gly	C
	GUA	Val	GCA	Ala	GAA	Glu	GGA	Gly	A
	GUG	Val	GCG	Ala	GAG	Glu	GGG	Gly	G

According to the above table; one amino acid has several triplets, but triplet code is unique for an amino acid. For Proline amino acid (Pro) there are 4 different but unique codons are there, which are CCU, CCC, CCA and CCG. Likewise, for each amino acid, there are several triplets. Therefore, for a particular amino acid sequence there can be different triplet codes.

5' CCU-CAA-GAA-GAU-UUU 3' is a one possible mRNA sequence for Pro-Gln-Glu-Asp-Phe sequence.

Interpretation Introduction

(c)

Interpretation:

Possible mRNA sequence that codes for Thr-Ser-Asn-Arg should be identified.

Concept Introduction:

Genetic code − 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 61P

5' ACU-UCU-AAU-CGU 3'

Explanation of Solution

Codons are written from 5 prime ends (5') to 3 prime ends (3') of mRNA. There is a specific sequence of nucleotides for each amino acid. The below-mentioned table represents the relationship between nucleotides and amino acids.

The Genetic Code- Triplets in Messenger RNA

First Base (5' end)	Second Base								Third Base (3' end)
	U		C		A		G
U	UUU	Phe	UCU	Ser	UAU	Tyr	UGU	Cys	U
	UUC	Phe	UCC	Ser	UAC	Tyr	UGC	Cys	C
	UUA	Leu	UCA	Ser	UAA	Stop	UGA	Stop	A
	UUG	Leu	UCG	Ser	UAG	Stop	UGG	Trp	G
C	CUU	Leu	CCU	Pro	CAU	His	CGU	Arg	U
	CUC	Leu	CCC	Pro	CAC	His	CGC	Arg	C
	CUA	Leu	CCA	Pro	CAA	Gln	CGA	Arg	A
	CUG	Leu	CCG	Pro	CAG	Gln	CGG	Arg	G
A	AUU	Ile	ACU	Thr	AAU	Asn	AGU	Ser	U
	AUC	Ile	ACC	Thr	AAC	Asn	AGC	Ser	C
	AUA	Ile	ACA	Thr	AAA	Lys	AGA	Arg	A
	AUG	Met	ACG	Thr	AAG	Lys	AGG	Arg	G
G	GUU	Val	GCU	Ala	GAU	Asp	GGU	Gly	U
	GUC	Val	GCC	Ala	GAC	Asp	GGC	Gly	C
	GUA	Val	GCA	Ala	GAA	Glu	GGA	Gly	A
	GUG	Val	GCG	Ala	GAG	Glu	GGG	Gly	G

According to the above table; one amino acid has several triplets, but triplet code is unique for an amino acid. For Threonine amino acid (Thr) there are 3 different but unique codons are there, which are ACU, ACC, ACA and ACG. Likewise, for each amino acid, there are several triplets. Therefore, for a particular amino acid sequence there can be different triplet codes.

5' ACU-UCU-AAU-CGU 3'is a one possible mRNA sequence for Thr-Ser-Asn-Arg sequence.