Molecular Biology: Comparison Between B and Z Structures of Dna

Molecular Biology

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NO.1

Comparison between B and Z structures of DNA

B-form DNA

The B-form DNA structure has two strands of the DNA each of them in the right-hand helix that are wound around the same axis. The two strands of the DNAS are held together by the hydrogen bond between the bases. The B-form structure of the DNA has a high humidity of 92%. The bases usually fit in the model of double helix if the pyrimidine on one of the strand is always paired with the purine on the other strand. From the rule of Chargaff’s the two strands of the DNA pair A with T and G with C. Two hydrogen bonds are capable of forming between A and T and, three are capable of forming between G and C. The third hydrogen bond in the in the base pair of G: C occurs between the additional exocyclic amino group on the G and the C2 keto group on C. The B-form structure has a pitch Å of 33.2 and residues per turn of approximately 10.

Z-form DNA

The Z-form DNA is a radically duplex structure that is different, with two strands that coil in the left-handed helices and have a zigzag pattern in the phosphodiester backbone. The Z-form DNA is capable of forming when the DNA is in an alternating sequence of purine-pyrimidine like GCGCGC, where the G and C nucleotides are in conformations that are different leading to a pattern that is a zigzag. The duplex in the Z-form DNA is supposed to accommodate the distortion of the G-nucleotide in the synconformation. The Z-form structure usually places the guanine back over the sugar-ring unlike to the usual anticonformation in the B-form structure. The Z-form DNA has pitch Å of 45.5 and the residues per turn is 12.

No.2

Standard PCR

The standard polymerase chain reaction utilizes the enzyme DNA polymerase to make the regions of the DNA that are selected from the initial DNA template. The standard polymerase chain reaction utilizes the following chemicals in making the DNA;

• A small quantity of the DNA that is utilized to the target sequence or initial template of the DNA.
• A couple of the primers that are made to join to each end of the initial template of the DNA and four dNTPs
• DNA polymerase enzymes and a few salts and ions that are in the class of essential

Procedure

The short pieces of the DNA are that usually hybridize to the sequences of DNA on either side of the piece of interest leads to the initiation of the synthesis of DNA via area X.

The copies of the both strands of X and that one of the initial DNA strands are the templates for the next cycle of the DNA synthesis

The region of the DNA that is selected now doubles in amount after every cycle of synthesis

Amplification of the DNA by standard PCR

The process of amplifying starts with the DNA template that is double-stranded, present in limited amounts, dNTPS, and two primers available in high amounts and complementary to the end of the DNA region to be amplified and a Taq polymerase.

During every cycle, the strands of the DNA template are usually separated by heating. The temperature is then lowered to ensure the primers to bind to the complementary strands that are being made.