Q.17.87 - An Introduction to General, Organic, and Biological Chemistry

Question

The following is a segment of the template strand of the human BRCA1 gene:

TGG AAT TAT CTG CTG TTC GCG 

a. Write the corresponding mRNA segment.

b. Write the three letters and one letter abbreviation for the corresponding peptide segment.

c. If there is a point mutation in the fourth nucleotide triplet and A replaces G, if any, in the amino acid sequence?

Step-by-Step Solution

Answer

a. The mRNA segment is  5' ACC UUA AUA GAC GAG AAG CGC 3' .

b.  Amino acids: Thr-Leu-Ile-Asp-Glu-Lys-Arg 

c. Amino acids: Thr-Leu-Ile-Asn-Glu-Lys-Arg 

Step 1: Part (a) Given information

The strand of the human BRCA1 gene is given as:

TGG AAT TAT CTG CTG TTC GCG 

Step 2: Part (a) Explanation

RNA differs from DNA in that it lacks nitrogenous base THYMINE and possesses URACIL instead. The base pairing will be as follows:

DNA       RNA

5'              3'

A   <---->   U

T   <---->   A

C   <---->   G

G   <---->   C

Hence the mRNA sequence will be as follows

DNA      3'  TGG AAT TAT CTG CTC TTC GCG 5'

RNA      5' ACC UUA AUA GAC GAG AAG CGC 3'

Step 1: Part (b) Explanation

The strand of the human BRCA1 gene is given as:

TGG AAT TAT CTG CTG TTC GCG 

Thus the corresponding mRNA segment will be given as: 

ACC UUA AUA GAC GAG AAG CGC 

Thus, the three-letter abbreviations for an amino acid is given as:

Amino acids: Thr-Leu-Ile-Asp-Glu-Lys-Arg

Note: Referring to the table given below:

Step 1: Part (c) Explanation

The strand of the human BRCA1 gene is given as:

TGG AAT TAT CTG CTG TTC GCG 

If the fourth nucleotide triplet and A replaces G  if any. Since in the fourth nucleotide there is no A. Thus the corresponding mRNA segment will be given as: 

ACC UUA AUA GAC GAG AAG CGC 

Thus, the three-letter abbreviations for an amino acid are given as:

Amino acids: Thr-Leu-Ile-Asp-Glu-Lys-Arg