Give brief definitions or unique descriptions of the following terms:

Give brief definitions or unique descriptions of the following terms:

A) neutral drift

B) sickle cell trait

C) secondary structure

D) torsion angle

E) domain

F) quaternary structure

Answer:

A) Neutral drift:

It is a process in population genetics that majors in the randomness of a change in allele frequencies where the change does not have any effect on the fitness of an organism. This again can cause variation within populations and in the long run fixation of neutral alleles might occur. One such event that brings change to the evolution process, is the neural drift that happens particularly more in small groups of evolution and produces the changes that are not a result of Natural selection.

B) Sickle cell trait:

Sickle cell trait on the other hand is one gene which one inherits but the other gene is normal hemoglobin. People with this engaging trait neither have complications of sickle cell disease but are capable of causing the gene to the upcoming generation. However, one should not confuse pathologic adaptation with protection since the sickle cell trait provides certain protection against malaria, which is why this gene is much more widespread in the territories where this tropical disease is widespread.

C) Secondary structure:

Secondary structure can be defined as the somewhat limited or usual twist of the polypeptide chain of a protein. Common types of secondary structures are alpha helices and beta sheets and the structure is stabilized by hydrogen bonds between the backbone atoms of the polypeptide bonds. They are the basic unit of the gross structure of the protein molecules and an ingredient in determining the functions and stability of the majority of the proteins.

D) Torsion angle:

The torsion angle or dihedral angle is defined as the angle that two planes containing four subsequent bonded atoms make with each other. Proteins have up to two torsion angles: phi, which denotes the rotation around the N-Cα bond and psi for the rotation around the Cα-C bond of the peptide backbone. Torsion angles is rather important for the description of protein conformation and it is customary to represent torsion angles in the form of the Ramachandran plots.

E) Domain:

A domain is a comprehensible structural and/or functional part of the protein that can fold independently from other parts of the protein. Domains may have their function as, for example, binding to other molecules or being engaged in some catalytic processes of chemical reactions. Many proteins contain several domains; such domains, can form part of a multitude of protein configurations that consequently lead to proteins with diverse functions.

F) Quaternary structure:

Quaternary structure refers to the arrangement of the protein subunits in case the protein is made up of folded proteins more than one. This level of protein structure is well facilitated by the binding of at least two or more dissimilar protein molecules also called subunits with the use of non-bonded interactions. Another structural level is quaternary structure which is as crucial to a protein’s functionality as the previous; for instance, hemoglobin is a protein that is made up of four polypeptide subunits that undertake the chore of ferrying oxygen in the bloodstream.