Dr. John H. Gillespie - Population Genetics_ A Concise Guide-The Johns Hopkins University Press (1997)

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https://www.differencebetween.com/difference-between-transition-and-vs-transversion/

Key Difference – Transition vs Transversion

It is important to have a general knowledge of base pairing in DNA in order to understand the difference between transition and transversion mutations. There are five different nitrogenous bases in nucleic acids: adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). First two bases (A & G) are purines while latter three (C, T and U) are pyrimidines. T is unique to DNA and U is unique to RNA. Purine bases form hydrogen bonds with complementary pyrimidine bases. It is known as a complementary base pairing of nucleic acids. Complement base of A is T in DNA. In RNA instead of T, U is present and A forms hydrogen bonds with U. Complement Base of G is C. Purine bases are composed of two ring systems and pyrimidine bases are composed of one ring systems. Mutations occur in DNA and RNA base sequences due to interchanges in base pairing. Substitution of an incorrect base during DNA replication repairs by DNA polymerase enzymes. However, transversion and transition are two such mutations that occur in DNA due to substitution errors, and they are not recognized by enzymes for repairing. Transition mutation occurs due to an interchange of purines or pyrimidines. Transversion mutation occurs due to interchanges of pyrimidine for purines or purines for pyrimidines. This is the key difference between transition and transversion.

CONTENTS

Overview and Key Difference What is Transition Mutation What is Transversion Mutation Side by Side Comparison – Transition and Transversion Summary

What is Transition Mutation?
Transition is a point mutation that occurs due to an interchange of purines (A ↔ G) or pyrimidines (C ↔ T) in DNA. It is a kind of a substitution mutation. During replication, the correct purine base can substitute another purine. For example, instead of A in the correct sequence, G can be substituted. Once G is substituted, complementary C will substitute to the other strand. In the same way, another pyrimidine base T can be substituted instead of pyrimidine base C and change the complementary base in the other strand. Transition mutations are more frequent than transversions. Single nucleotide polymorphism is a common type of point mutations, and two out of three SNPs are caused by transitional mutations. However, transition mutations are less likely to cause amino acid sequence changes. Hence, they remain neutral and are known as silent mutations.

Difference Between Transition and Transversion - 1
Figure 01: A Transition Mutation
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What is Transversion Mutation?
Transversion is the second type of point mutation that occurs due to the wrong substitution of bases. Transversion happens when a purine base is substituted with a pyrimidine base, or a pyrimidine base is substituted with a purine base as shown in figure 02.
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Key Difference - Transition vs Transversion
Figure 02: A Transversion Mutation

Transversion occurs in two possible ways since two pyrimidines and two purines are present. This type of mutation is less likely to produce incorrect amino acid sequences during translation.

Transversions are caused by ionizing radiation, strong chemicals, etc.

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Type Definition
A type specimen is a specimen selected to serve as a reference point when a plant species is first named. As a result, these specimens are extremely important to botanists who are attempting to determine the correct application of a name. They are often specially curated in herbaria, such as at the NYBG, where they are filed separately. There are several different categories of types; the most common are:

Holotype: The single specimen designated as the type of a species by the original author at the time the species name and description was published.

Isotype: A duplicate specimen of the holotype.

Syntype: Any of two or more specimens listed in the original description of a taxon when a holotype was not designated.

Isosyntype: A duplicate of a syntype.

Paratype: A specimen not formally designated as a type but cited along with the type collection in the original description of a taxon.

Lectotype: A specimen chosen by a later researcher to serve as if it were the holotype. It is chosen from among the specimens available to the original publishing author (the isotypes, syntypes and/or paratypes) of a scientific name when the holotype was either lost or destroyed, or when no holotype was designated.

Neotype: A specimen chosen by a later researcher to serve in place of a holotype when all specimens available to the original publishing author of a scientific name have been lost or destroyed.

Topotype: A specimen of a plant collected from the same locality as the holotype and usually on a different date. A topotype has no formal standing. = locotype

Cotype: A term formerly used for syntype and sometimes (erroneously) for isotype and paratype. This is an old term that was used loosely and is not used by today's taxonomists.

Generitype: The type specimen of a genus. It is designated by using the type for the name of a particular species within that genus. For example, the generitype for Aster is the type for Aster amellus L.

For further information on the Vascular Plant Type Specimens Imaging Project, please contact our Imaging Coordinator.

https://sciweb.nybg.org/science2/herbarium_imaging/typedefinition.asp.html#:~:text=Topotype%3A A specimen of a,topotype has no formal standing. %3D

A quantitative trait locus (QTL) is a locus (section of DNA) that correlates with variation of a quantitative trait in the phenotype of a population of organisms.[1] QTLs are mapped by identifying which molecular markers (such as SNPs or AFLPs) correlate with an observed trait. This is often an early step in identifying and sequencing the actual genes that cause the trait variation.

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Complex traits, also known as quantitative traits, are traits that do not behave according to simple Mendelian inheritance laws. More specifically, their inheritance cannot be explained by the genetic segregation of a single gene. Such traits show a continuous range of variation and are influenced by both environmental and genetic factors. Compared to strictly Mendelian traits, complex traits are far more common, and because they can be hugely polygenic, they are studied using statistical techniques such as QTL mapping rather than classical genetics methods.[1] Examples of complex traits include height, circadian rhythms, enzyme kinetics, and many diseases including diabetes and Parkinson's disease. One major goal of genetic research today is to better understand the molecular mechanisms through which genetic variants act to influence complex traits.

https://www.sciencedaily.com/terms/allele.htm