In: Biology
One strand of a double-helical DNA has the sequence 5'-GCGCAATATTTCTCAAAATATTGCGC-3'. Write the base sequence of the complementary strand. What special type of sequence is contained in this DNA segment? Does this double-stranded DNA have the potential to form any alternative structures?
Answer 1: The given DNA sequence along with the complementary strand sequence is shown below in bold letters.
5'-GCGCAATATTTCTCAAAATATTGCGC-3'
3’-CGCGTTATAAAGAGTTTTATAACGCG-5’
Answer 2: in this strand there is a palindromic sequence . Palindromic sequence is a nucleotide sequence which will remain same even if the direction of reading is changed on the complementary strand.
5'-GCGCAATATTTCTCAAAATATTGCGC-3'
I II
3’-CGCGTTATAAAGAGTTTTATAACGCG-5’
III IV
In this example, sequence I matches with sequence IV and sequence II matches with sequence III , if the reading direction is reversed. Hence this is an example of palindromic sequence.
Answer 3: If only 5’to 3’ strand is considered, we can see the sequences are complementary on the first half and last half, hence a single strand can form a hairpin sturucture. Similar thing can be said about the 3’ to 5’ strand.
Or the double strands can form a cruciform structure