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For many of the loci, trinucleotide expansion is harmless, [citation needed] but in some areas expansion has detrimental effects that cause symptoms. When the trinucleotide repeat is present within the protein-coding region, the repeat expansion leads to production of a mutant protein with gain of function .
Generally, the larger the expansion the more likely they are to cause disease or increase the severity of disease. Other proposed mechanisms for expansion and reduction involve the interaction of RNA and DNA molecules. [3] In addition to occurring during DNA replication, trinucleotide repeat expansion can also occur during DNA repair. [4]
In these examples, the source of selection on a trait coevolves with the trait itself, therefore causation is reciprocal and developmental processes potentially become relevant to evolutionary accounts. For instance, a peacock’s tail evolves through mating preferences in peahens, and those preferences coevolve with the male trait.
In genetics, trinucleotide repeat disorders, a subset of microsatellite expansion diseases (also known as repeat expansion disorders), are a set of over 30 genetic disorders caused by trinucleotide repeat expansion, a kind of mutation in which repeats of three nucleotides (trinucleotide repeats) increase in copy numbers until they cross a threshold above which they cause developmental ...
Cell growth refers to an increase in the total mass of a cell, including both cytoplasmic, nuclear and organelle volume. [1] Cell growth occurs when the overall rate of cellular biosynthesis (production of biomolecules or anabolism) is greater than the overall rate of cellular degradation (the destruction of biomolecules via the proteasome, lysosome or autophagy, or catabolism).
One example comes from the human influenza virus, which has been involved in an adaptive contest with humans for hundreds of years. While antigenic drift (the gradual change of surface antigens) is considered the traditional model for changes in the viral genotype, recent evidence [ 7 ] suggests that selective sweeps play an important role as well.
For example, Denis Noble says that using terms and categories of the modern synthesis distorts the picture of biology that modern experimentation has discovered. [91] Proponents therefore claim that the extended synthesis is necessary to help expand the conceptions and framework of how evolution is considered throughout the biological disciplines.
Snakes are a particularly good example for studying limb loss, as they underwent limb loss and regeneration multiple times throughout their evolution before they finally lost their legs for good. Much of the gene expression during embryonic development is regulated via spatiotemporal and chemotactic signaling, [ 20 ] as depicted by the image to ...