Question

The following sequence is a fragment from the normal version of the Social B gene of Solenopsis daguerrei ants. You may need to use the codon table provided.

DNA SocialB: 5’- ATG TCG GTA GCA TGT GTC TGC-3’

A transition mutation in the sequence results in a change in the 3^rd amino acid of the polypeptide chain: Alanine is produced. The DNA sequence with the mutation (the one used to name the SNP 5’ to 3’) is_______.

Options -

a. 5’- ATG TCG GCA GCA TGT GTC TGC-3’

b. 5’-CGT CTG TGT ACG ATG GCT GTA-3’

c. 3’- TAC AGC CAT CGT ACA CAG ACG-5’

d. 5’- AUG UCG GUA GCA UGU GUC UGC-3’

e. 5’-ATG TCG GTA GCA ATC GTC TGC-3’

Answer 1

Answer: a. 5’- ATG TCG GCA GCA TGT GTC TGC-3’

Explanation: Following conversion can be followed for the transcription (DNA to mRNA) and translation (mRNA to protein):

DNA	mRNA
A-T	A-U
T-A	T-A
C-G	C-G
G-C	G-C

- And for protein conversion one can follow the genetic codon table available as a free resource on internet.

- The provided strand in sense strand (5'-->3') of DNA sequence. This sense strand gets converted into template strand (3' --> 5') via complementary pairing.

- This template strand gets transcribed into RNA. Then this RNA forms codons int order to translate into amino acids.

DNA Social B
Sense Strand	5'- ATG TCG GTA GCA TGT GTC TGC-3'
Template Strand	3'- TAC AGC CAT CGT ACA CAG ACG-5'
mRNA	5'- AUG UCG GUA GCA UGU GUC UGC-3'
Protein	MET SER VAL ALA CYS VAL CYS

Protein	MET	SER	VAL	ALA	CYS	VAL	CYS
Number	1	2	3	4	5	6	7

- In here third amino acid codon codes for valine.

- Transition mutation is a mutation in which purine gets mutated to other purine (A-G or G-A) or pyrimidine gets converted to other pyrimidine (C-T or T-C).

- In here it is said that the third amino acid gets converted to alanine due to transition mutation. Only option A supports this fact.

Option a
Sense Strand	5'- ATG TCG GCA GCA TGT GTC TGC-3'
Template Strand	3'- TAC AGC CGT CGT ACA CAG ACG-5'
mRNA	5'- AUG UCG GCA GCA UGU GUC UGC-3'
Protein	MET SER ALA ALA CYS VAL CYS

- In here T gets mutated to C. (pyrimidine to pyrimidine)

Protein	MET	SER	ALA	ALA	CYS	VAL	CYS
Number	1	2	3	4	5	6	7

.Other options:

- Option b: Cysteine is formed as the third amino acid in the sequence.

-Option c: Histidine is formed as the third amino acid in the sequence.

- Option d: This is RNA sequence. Question is about DNA sequence.

- Option e: Valine is formed as the third amino acid in the sequence.