In: Biology
Which one of the following DNA chains is both complementary and anti-parallel to this DNA chain: 5' GGGTTT 3'? (it can be more than one answer)
5' TTTGGG 3'
5' GGGTTT 3'
5' CCCAAA 3'
5' AAACCC 3'
The correct option is (d) 5' AAACCC 3'.
In DNA double helix, one strand is complementary and antiparallel to the other strand. In DNA, adenine is complementary to thymine whereas guanine is complementary to cytosine. If one strand is in 3' to 5' direction, then the other strand will be in 5' to 3' direction.
Here, in the above question, the given DNA chain is in 5' to 3' direction and guanine is present at the 5' end and thymine is present at the 3' end. So according to complementarity and antiparallel property of DNA, cytosine should be present at the 3' end and thymine should be present at the 5' end. Hence the correct option is 5' AAACCC 3'.
Option (a) and (b) are incorrect because bases in these chains are not complementary to the given chain.
Option (c) is incorrect because bases in this chain are complementary to the given chain but they are present on wrong ends as the cytosine is present at the 5' end which is complementary to the guanine at 5' end but then they will not be antiparallel.