Question

You can represent a dna segment by writing out the sequence of its base pairs. which of the following sequences represents a correct dna segment?

a. 5'-g t c c a-3' 5'-c a g g t'-3'
b. 5'-g t c c a-3' 3'-c a g g t'-5'
c. 5'-g t c c a-3' 3'-c a g g t'-3'
d. 5'-g t c c a-3' 5'-c a g g t-5'

Answer 1

The correct DNA segment that has a complementary sequence to 5'-ATTCCGGATCGA-3' is 5'-TAAGGCCTAGCT-3', which is option A. DNA strands are antiparallel and follow base pairing rules: Adenine pairs with Thymine, and Cytosine pairs with Guanine.

Step-by-step explanation:

To determine which sequence represents a correct DNA segment, we need to remember the base pairing rules: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G). DNA strands are antiparallel, which means one strand runs from 5' to 3' and the complementary strand runs from 3' to 5'. Given the DNA segment 5'-ATTCCGGATCGA-3', the correct complementary strand would have to be antiparallel and follow base pairing rules. Therefore, the sequence of the complementary DNA strand would be 3'-TAAGGCCTAGCT-5'. This matches option A.

If the sequence of the 5'-3' strand is AATGCTAC, then according to the base pairing rules the complementary sequence would be 3'-TTACGATG-5'.

These examples demonstrate how complementary sequences are determined in DNA molecules. For practice, given the sequence 5'-G T C C A-3', the correct complementary sequence, following the base pairing rules and the antiparallel orientation, would be 3'-C A G G T-5' which corresponds to option B in the original question.