Q.17.88 - An Introduction to General, Organic, and Biological Chemistry

Question

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

ACA TAT TTT GCA AAT TTT GCA 

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 second nucleotide triplet and C replaces A, if any, in the amino acid sequence?

Step-by-Step Solution

Answer

a. UGU AUA AAA CGU UUA AAA CGU

b. Cys(C), Ile(I), Lys(K), Arg(R), Leu(L), Lys(K), Arg(R)

c. Cys(C), Arg(R), Lys(K), Arg(R), Leu(L), Lys(K), Arg(R)

Step 1: Given information

The template strand of the human BRCA1 gene:

ACA TAT TTT GCA AAT TTT GCA 

Step 1: 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

The template strand of the human BRCA1 gene:

ACA TAT TTT GCA AAT TTT GCA 

Thus, the corresponding mRNA segment is given as:

UGU AUA AAA CGU UUA AAA CGU 

Step 1: Part (b) Explanation

The template strand of the human BRCA1 gene:

ACA TAT TTT GCA AAT TTT GCA 

Thus, the corresponding mRNA segment is given as:

UGU AUA AAA CGU UUA AAA CGU 

According to 64 codon codes to amino acids, UGU codes for Cysteine, AUA codes for Isoleucine, AAA for lysine, CGU for Arginine, UUA for Leucine, CGU for Arginine.

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

Amino acids: Cys(C), Arg(R), Lys(K), Arg(R), Leu(L), Lys(K), Arg(R) 

Note: Referring to the table given below: 

Step 1: Part (c) Explanation

The template strand of the human BRCA1 gene:

ACA TAT TTT GCA AAT TTT GCA 

Thus, the corresponding mRNA segment is given as:

UGU AUA AAA CGU UUA AAA CGU 

If the second nucleotide triplet and C replaces A 

The resulting BRCA1 gene segment is ACA TCT TTT GCA AAT TTT GCA, 

then mRNA segment is UGU AGA AAA CGU UUA AAA CGU

The amino acid sequence will be Cys(C), Arg(R), Lys(K), Arg(R), Leu(L), Lys(K), Arg(R)