Antiparallel: A term applied to two molecules that are side by side but run in opposite directions. The two strands of DNA are antiparallel. The head of one strand is always laid against the tail of the other strand of DNA. CONTINUE SCROLLING OR CLICK HERE In biochemistry, two biopolymers are antiparallel if they run parallel to each other but with opposite directionality (alignments). An example is the two complementary strands of a DNA double helix, which run in opposite directions alongside each other.
Nucleic acid molecules have a phosphoryl (5') end and a hydroxyl (3') end. This notation follows from organic chemistry nomenclature, and can be used to define the movement of enzymes such as DNA polymerases relative to the DNA strand in a non-arbitrary manner.
G-quadruplexes, also known as G4 DNA are secondary structures found in nucleic acids that are rich in guanine.[1] These structures are normally located at the telomeres (the ends of the chromosomes). The G-quadruplex can either be parallel or antiparallel depending on the loop configuration, which is a component of the structure. If all the DNA strands run in the same direction, it is termed to be a parallel quadruplex, and is known as a strand-reversal/propeller, connecting adjacent parallel strands. If one or more of the DNA strands run in opposite direction, it is termed as an anti-parallel quadruplex, and can either be in a form of a lateral/edgewise, connecting adjacent anti-parallel strands, or a diagonal, joining two diagonally opposite strands.[2] The structure of these G-quadruplexes can be determined by a cation. DNA replicationIn DNA, the 5' carbon is located at the top of the leading strand, and the 3' carbon is located at the lower section of the lagging strand. The nucleic acid sequences are complementary and parallel, but they go in opposite directions, hence the antiparallel designation.[3] The antiparallel structure of DNA is important in DNA replication because it replicates the leading strand one way and the lagging strand the other way. During DNA replication, the leading strand is replicated continuously whereas the lagging strand is replicated in segments known as Okazaki fragments. Anti-parallelism in biochemistryThe importance of an antiparallel DNA double helix structure is because of its hydrogen bonding between the complementary nitrogenous base pairs. If the DNA structure were to be parallel, the hydrogen bonding would not be possible, as the base pairs would not be paired in the known way.[4] The four base pairs are: adenine, guanine, cytosine, and thymine, where adenine complements thymine, and guanine complements cytosine. Transcription would be another problem if the DNA structure were to be parallel, making no sense of the information being read from the DNA. This would further lead to the production of incorrect proteins.[5] Polypeptides have an N-terminus and a C-terminus, which refer to the ends of the polymer in a way that reflects the direction in which the polymer was synthesized. The chronological sequence of each amino acid sub-unit is the basis for directionality notation in polypeptides; a given protein can be represented as its set of unique amino acid abbreviations within an N-terminus and a C-terminus. Beta sheetAntiparallel and parallel beta sheet Many proteins may adopt a beta sheet as part of their secondary structure. In beta sheets, sections of a single polypeptide may run side-by-side and antiparallel to each other, to allow for hydrogen bonding between their backbone chains. Beta sheets can also be either a parallel or anti-parallel secondary structure. However, an anti-parallel beta sheet is significantly more stable than a parallel structure due to their well aligned H-bonds, which are at a 90° angle.[6]
My biology textbook mentions that DNA is antiparallel and it got me wondering... Can DNA be parallel? What would happen if it was parallel? could DNA still replicate right? 3 Answers By Expert Tutors
Jesse E. answered • 06/11/19 Masters in Chemistry and Bachelors in Biology
In antiparallel DNA, one strand runs from 5´ to 3´ prime and the other strand runs form 3´ to 5 ´. This configuration allows the DNA strands to form complementary pair their nucleotides using hydrogen bonds. This configuration allows for the enymes of DNA replication to function. If the DNA strand was parallel, replication would not be possible. The nucleotides would not be complementary to each other and, as a result, would not pair in a genetic molecule. Therefore, the DNA being antiparallel is the only way replication and life could occur.
Lauren H. answered • 03/16/19 Experienced High School Chemistry Teacher
From the Internet: Antiparallel: A term applied to two molecules that are side by side but run in opposite directions. The two strands of DNA are antiparallel. The head of one strand is always laid against the tail of the other strand of DNA. The molecule is constructed in this manner so that each nucleotide has an opposite match (G with C and A with T). This allows for the translation into mRNA which carries the "code" of triplets out into the cytoplasm to serve as a template for protein production.
DNA has to be antiparallel. The antiparallel nature allows two strands to go in opposite direction. Which ultimately facilitate forming daughter DNA into two different directions and preety helpful during polymerase chain reaction that amplify DNA to make multiple copies of it. if two strands of DNA were parallel there will not be any replication bubble as there is no leading strand and lagging strand ( both strands will be leading strands). |