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Flashcards in DNA Enzymes Deck (13):

What does polymerase catalyse?

The condensation synthesis of DNA and RNA nucleic acid polymers. Hydrogen bonding between complementary pair of monomer nucleotides and the base sequence of a template strand organises the nucleotides into the correct position and sequence.


What do Polymerases catalyse?

Catalyse the formation of a phosphodiester bonds between a nucleotide and the nucleic acid of the newly synthesised strand. This new strand can be synthesised by polymerase in a 5' to 3' direction only.


What is the formula for Polymerases?

DNA nucleotide (monomer) + DNA (polymer) -------DNA polymerase-----> DNA (longer polymer) + water

RNA nucleotide (monomer) + RNA (polymer) -------RNA polymerase----->RNA (longer polymer) + water


What do Polymerases catalyse?

The addition of monomers (nucleotides) onto the end of a strand of polymer (the nucleic acid), a short sequence of polymer complementary to the start of the template strand is required to initiate Polymerisation. These short single-stranded sequences are known as primers.


What needs to be used in cyclic reactions involved in PCR and DNA sequencing?

A thermostable DNA polymerase must be used. This DNA polymerase has been cloned from a hot-spring bacterium, thermus aquaticus, and is stable to 95 Celsius. It's usually referred to as Taq Polymerase.


What is DNA ligase?

It catalyses the condensation synthesis of phosphodiester bonds between two strands of nucleic acid polymer. In DNA replication, it joins the sugar-phosphate backbone between fragments of DNA as they are synthesised on the lagging strand.


What is the formula for DNA ligase?

DNA (polymer) + DNA (polymer) -------DNA ligase----> DNA (longer polymer) + water


What are sticky ends and blunt ends?

All restriction enzymes cut phosphodiester bonds at specific nucleotide base sequences. Some restriction enzymes cut straight across the DNA strand, breaking the two phosphodiester bonds opposite one another and producing DNA with what are known as blunt ends. However, most restriction enzymes make a staggered cut in DNA, hydrolysis a phosphodiester bond on each strand several base pairs apart. The staggered cut is known as a sticky end.


What is an advantage of blunt-ended DNA fragments?

They can be joined with any other blunt-ended fragment. An advantage of sticky ends is that is that the short sections of single-stranded DNA at the ends only form hydrogen bonds with complementary single-stranded sequences. This means the DNA fragments with sticky ends will hybridise with other DNA fragments produced by the same restriction enzyme, but not with fragments produced by a different restriction enzyme.


What are endonucleases?

They catalyse the hydrolytic degradation of phosphodiester bonds. In digestion, they catalyse the complete breakdown of nucleic acid polymers into nucleotide monomers.


What is the formula for endonucleases?

DNA (polymer) + water -------(endonuclease)-------> DNA nucleotides (monomers)


What are restriction endonucleases?

Often referred to as a restriction enzymes also break the phosphodiester bonds between adjacent nucleotides in a sequence but they are restricted to making the cut between a specific sequence of nucleotide bases.


What is the formula for restriction enzymes?

DNA (polymer) + water----(restriction endonucelase)-----> DNA (shorter polymer) + DNA (shorter polymer)