When the complementary strand is read backwards, the sequence is 5’-GGATCC-3’ which is identical to the first one, making it a palindromic sequence. This is the sequence where the restriction endonuclease, BamHI, binds to and cleaves at a specific cleavage site. An example of a palindromic sequence is 5’-GGATCC-3’, which has a complementary strand, 3’-CCTAGG-5’. So if a sequence is palindromic, the nucleotide sequence of one strand would be the same as its reverse complementary strand. The word palindrome first appeared in English in the 1620s, when poet and playwright Ben Johnson coined the phrase. ![]() For example, the word did, the number 1991, and the sentence Able was I ere I saw Elba are all palindromes. The pairing of nucleotides within the DNA double-helix is complementary which consist of Adenine (A) pairing with either Thymine (T) in DNA or Uracil (U) in RNA, while Cytosine (C) pairs with Guanine (G). A palindrome (PAL-en-drohm) is a word, sentence, or number that can be read the same way backwards and forwards. ![]() Recognition sites of many restriction enzymes are palindromic. ![]() The sequence is the same when one strand is read left to right and the other strand is read right to left. Here, for example, the single difference in the sequences can be eliminated (red for blue or vice versa).A DNA sequence whose 5'-to-3' sequence is identical on each DNA strand. Repairs can then be made (probably by the mechanism of homologous recombination). All that is needed is to form a loop so that the two sequences line up side-by-side. This orientation and redundancy may help ensure that a deleterious mutation in one copy of the set can be repaired using the information in another copy of that set. GTGTT AAGGGTACCCAACACCCTC 5' - 3' GAGGGTGTTGGGTACCCT AAACAC. 5' to 3') on one strand is identical to the sequence in the same direction (e.g. CACAA TTCCCATGGGTTGTGGGAG 3' - 5' CTCCCACAACCCATGGGA TTTGTG. A palindromic sequence is a nucleic acid sequence in a double-stranded DNA or RNA molecule whereby reading in a certain direction (e.g. (The dashes represent the thousands of base pairs that separate adjacent palindromes.)ĥ'. This sequence-specific restriction digestion evolved as a defense mechanism against invading viruses and has been adapted for DNA manipulation (i.e., molecular cloning) in research labs. The human Y chromosome contains 7 sets of genes - each set containing from 2 to 6 nearly-identical genes - oriented back-to-back or head-to-head that is, they are inverted repeats like the portion shown here. In bacteria, palindromic inverted repeats are recognition sites for sequence-specific restriction enzymes that cut the DNA within the palindrome (Fig. Inverted repeats at either end of retroviral gene sequences aid in inserting the DNA copy into the DNA of the host.The DNA of many transposons is flanked by inverted repeats such as this one:ĥ' GGCCAGTCACAATGG.~400 nt.CCATTGTGACTGGCC 3'ģ' CCGGTCAGTGTTACC.~400 nt.GGTAACACTGACCGG 5'.This graphic shows the "recognition helix" to which the CAP protein (a homodimer) binds in the lac operon of E. Transcription factors are often dimers of identical proteins (" homodimers") so it is not surprising that each member of the pair needs to "see" the same DNA sequence in the same orientation. The DNA sequence shown above is that of the glucocorticoid response element where n represents any nucleotide. ![]() The DNA to which transcription factors bind.In these cases, two different segments of the double helix read the same but in opposite directions. The graphic shows the palindromic sequences "seen" by five restriction enzymes (named in blue) commonly used in recombinant DNA work. This type of palindrome serves as the target for most restriction enzymes. Palindromes that occur on opposite strands of the same section of DNA helix. " able was I ere I saw elba" is a palindrome.ġ. A palindrome is a sequence of letters and/or words, that reads the same forwards and backwards.
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