Question

What are palindromic nucleotide sequences?

Answer 1

Hint: A palindromic sequence is the same forwards and backward on both sides. The enzyme recognizes the sequence doesn’t matter from which side the enzyme approaches the DNA. The palindromic sequence has an important role in molecular biology, as the DNA sequence is double-stranded and by reading base pairs palindromes can be determined. Palindromic sequences are typically 3 to 5 bases in length. Importance of this sequence is that it reads the same in both directions.

Complete answer:
A palindromic sequence is defined as a nucleotide sequence in a double-stranded DNA or RNA, when we read it from 5' end to 3' end is the same as that on the complementary strand reading from 3' end to 5' end.

For example:
5'-GAATTC-3'
3'-CTTAAG- 5'

- The top strand reads from 5' -GAATTC -3' and the bottom strand reads 3' -CTTAAG -5'.
- This palindromic sequence is recognized by the enzyme EcoR1.
- If in case, the DNA strand is flipped over, the sequence is exactly the same.
- The palindromic sequence also consists of methylation sites where a methyl group can be attached to the palindromic sequence.
- Methylation inactivates the resistant gene this is known as insertional mutagenesis or insertional inactivation.

Additional information:
- Two paired antiparallel strands of nucleotides that run in opposite directions form a double helix.
- The nucleotide pairing is like that adenine(A) pairs with thymine(T) in DNA or uracil(U) in RNA, cytosine(C) with guanine(G).
- A palindromic nucleotide sequence forms a hairpin.
- BamH1 recognizes this sequence 5' GGATCC 3' and 3' CCTAGG 5'.

Note: A palindromic sequence is a sequence in double-stranded DNA or RNA molecule in which reading in a 5'- 3' on one strand matches the sequence reading in the same direction on the complementary strand. Specific palindromic sequences are recognized by the restriction enzymes (restriction endonucleases) and cut them. Palindromes are also found frequently in the peptide sequences that make proteins, but their role in the protein function is unknown. It plays an important role in processes of transcription, replication, and repair mechanisms which are directional.