Mutations arise from errors in DNA replication or from environmental factors and can cause changes to single bases, larger DNA segments, or chromosome structure. Novel variants spread through populations by genetic drift or natural selection. Molecular data is used in taxonomy to describe evolutionary relationships, with species sharing a common ancestor and higher taxa descended from each other. However, morphology and molecules sometimes conflict, with one type of data showing multiple lineages or morphologies where the other shows a single one, possibly due to neutral evolution. Research on molecular evolution is published in specialized journals and informs understanding of genome architecture and the origin of novel genes.

1. GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE AND
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Maulana Abul Kalam Azad University of Technology
MODES OF MOLECULAR EVOLUTION
Shreya Panja
31308421033
2022-2023
BiologicalDiversityAnd Taxonomy
GEMc-302

2. B. Sc./ SEM 3/2022-23/ /Paper name/ Paper Code/Presentation_1
INTRODUCTION
Molecular evolution is the process of change
in the sequence composition
of cellular molecules such as DNA, RNA,
and proteins across generations. The field of
molecular evolution uses principles
of evolutionary biology and population
genetics to explain patterns in these changes.
Major topics in molecular evolution concern
the rates and impacts of single nucleotide
changes, neutral evolution vs. natural
selection, origins of new genes, the genetic
nature of complex traits, the genetic basis
of speciation, evolution of development, and
ways that evolutionary forces
influence genomic and phenotypic changes.

3. B. Sc./ SEM 3/2022-23/ /Paper name/ Paper Code/Presentation_1
Forces in molecular evolution
The content and structure of a genome is the product of the molecular and population genetic forces which
act upon that genome. Novel genetic variants will arise through mutation and will spread and be maintained
in populations due to genetic drift or natural selection.
Mutations are permanent, transmissible changes to the genetic material (DNA or RNA) of a cell or virus.
Mutations result from errors in DNA replication during cell division and by exposure to radiation, chemicals,
and other environmental stressors, or viruses and transposable elements. Most mutations that occur
are single nucleotide polymorphisms which modify single bases of the DNA sequence, resulting in point
mutations. Other types of mutations modify larger segments of DNA and can cause duplications, insertions,
deletions, inversions, and translocations.

4. B. Sc. / SEM 3/2022-23/ /Paper name/ Paper Code/Presentation_1
• How is taxonomy and evolution related?
 In modern taxonomy, that means describing
evolutionary links. A taxonomic group must
always refer to a set of organisms that
descended from the same ancestor, at
some point in evolutionary history. Species
within the same genus all share a common
ancestor. The same goes for each genus
within one family and so on. Thus,
molecular approaches have found a niche in
taxonomy. Measurement of DNA
hybridization between strains is the single
most definitive tool for defining a species.
Data on sequences of DNA and amino acids
can be used to infer phylogeny. It helps in
reconstructing the genetic relationship
between various species. It helps in the
study of evolution in a sequential manner. It
helps in finding the time of divergence
occurring between the various species.

5. CONCLUSION
B. Sc./ SEM 3/2022-23/ /Paper name/ Paper Code/Presentation_1
There are sometimes discordances between molecular and morphological evolution, which are reflected in molecular
and morphological systematic studies, especially of bacteria, archaea and eukaryotic microbes. These discordances can
be categorized as two types: (i) one morphology, multiple lineages (e.g. morphological convergence, cryptic species)
and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity, multiple life-cycle stages). Neutral
evolution possibly could explain the incongruences in some cases.
The Society for Molecular Biology and Evolution publishes the journals "Molecular Biology and Evolution" and "Genome
Biology and Evolution" and holds an annual international meeting. Other journals dedicated to molecular evolution
include Journal of Molecular Evolution and Molecular Phylogenetics and Evolution. Research in molecular evolution is
also published in journals of genetics, molecular biology, genomics, systematics, and evolutionary biology.

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REFERENCES
• Li, W.-H. (2006). Molecular Evolution. Sinauer. ISBN 0-87893-480-4.
• Lynch, M. (2007). The Origins of Genome Architecture. Sinauer. ISBN 978-0-87893-484-3.
• A. Meyer (Editor), Y. van de Peer, "Genome Evolution: Gene and Genome Duplications and the Origin of
Novel Gene Functions", 2003, ISBN 978-1-4020-1021-7
• T. Ryan Gregory, "The Evolution of the Genome", 2004, ISBN 978-0123014634
• Levinson, Gene (2020). Rethinking evolution: the revolution that's hiding in plain sight. World Scientific.
ISBN 9781786347268