ANSWER: (D) Restriction endonucleaseREF: Basic Genetics: Textbook and Activities by Ahmed Abouelmagd, Hussein M. Ageely page 117A palindromic sequence is a nucleic acid sequence {DNA or RNA) that is the same whether read 5' (five-prime) to 3' (three prime) on one strand or 5' to 3' on the complementary strand with which it forms a double helix.A restriction enzyme (or restriction endonuclease) is an enzyme that cuts DNA at specific recognition nucleotide sequences (with Type II restriction enzymes cutting double-stranded DNA) known as restriction sites. Such enzymes, found in bacteria and archaea, are thought to have evolved to provide a defense mechanism against invading viruses. Inside a bacterial host, the restriction enzymes selectively cut up foreign DNA in a process called restriction; host DNA is methylated by a modification enzyme (a methylase) to protect it from the restriction enzyme's activity. Collectively, these two processes form the restriction modification systemRestriction enzymes recognize a specific sequence of nucleotides and produce a double-stranded cut in the DNA. While recognition sequences vary betwreen 4 and 8 nucleotides, many of them are palindromic, wrhich correspond to nitrogenous base sequences that read the same backwards and forwards. In theory, there are two types of palindromic sequences that can be possible in DNA.The mirror-like palindrome is similar to those found in ordinary text, in which a sequence reads the same forward and backwards on a single strand of DNA strand, as in GTAATG.The inverted repeat palindrome is also a sequence that reads the same forward and backwards, but the forward and backward sequences are found in complementary DNA strands (i.e., of double-stranded DNA), as in GTATAC (GTATAC being complementary to CATATG). Inverted repeat palindromes are more common and have greater biological importance than mirror-like palindromes.Naturally occurring restriction endonucleases are categorized into four groups (Types I, II III, and IV) based on their composition and enzyme cofactor requirements, the nature of their target sequence, and the position of their DNA cleavage site relative to the target sequenceCategoryFunctionCofactors requiredCleavageType IMultifunctional protein with both restriction and DNA modify-cation (methylase) activityMg2+, ATP SAM (S- adenosylmethionine)Cleave DNA at non specific sites usually remote from recognition siteType IISingle function (restriction) en-zymes independent of methylaseOnly Mg2+Site specific 8t cleave writhin or at short specific distances from recognition siteType IIICombine restriction and DNA modification (methylase) activity in a single enzyme complex with different subunitsMg2+, SAM stimulates reaction but is not requiredCleave at sites a short distance from recognition siteHere are some restriction enzymes and the palindromic sequences which they recognizeEnzymeSourceRecognition SequenceCutEcoRlEscherichia coli5'GAATTC3'CTTAAG5---G AATTC---3'3---CTTAAG---5'BamH1Bacillus amylobquefaciens5'GGATCC3'CCTAGG5'---G GATCC---3'3'---CCTAG G---5'Taq1Thermus aquaticus5'TCGA3'AGCT5'---T CGA--3'3'---AGC T---5'Alul*Arthrobacter luteus5'AGCT3'TCGA5'---AG CT---3'3'---TC GA---5'* = blunt ends