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11.1 Genetic Variation Within Populations
11.1 Genetic Variation Within Populations

... The gall fly and its predators provide an excellent example of stabilizing selection. During stabilizing selection, the intermediate phenotype is favored and becomes more common in the population. That is, the distribution becomes stable at the intermediate phenotype rather than shifting toward one ...
Functional and Evolutionary Analysis of Flowering Time Genes in
Functional and Evolutionary Analysis of Flowering Time Genes in

... variation. Thus much evolutionary research is focused on detecting positively selected sites, because these sites can tell us something about ongoing evolution. However, examples of coding regions under positive selection are rare. In many cases where positive selection is invoked, the genes are sel ...
1 Epistasis Underlying a Fitness Trait within a Natural
1 Epistasis Underlying a Fitness Trait within a Natural

... founder events. The two assumptions were that post-glacial dispersal had taken place by sequential founder events along a latitudinal gradient and that there is actually epistatic variation for photoperiodic response within populations. The first of these assumptions was supported by Armbruster et a ...
ª2010 Elsevier Ltd All rights reserved DOI 10.1016/j.cub.2010.06.022
ª2010 Elsevier Ltd All rights reserved DOI 10.1016/j.cub.2010.06.022

... ecological isolation [3, 4] and Dobzhansky-Muller (DM) interaction [5]. Under ecological isolation, populations adapt to divergent environments through the accumulation of genetic changes that result in increased fitness. If formed, hybrid populations are genotypically intermediate and therefore sub ...
Selection  - Integrative Biology
Selection - Integrative Biology

... Relative fitness: the average number of offspring produced by individuals with a certain genotype, relative to the number produced by individuals with other genotypes. Quantitative trait: determined by a large number of genes each of small effect and environmental factors, e.g., height and weight (F ...
Evolutionary implications of non- neutral
Evolutionary implications of non- neutral

... characteristics of mutational changes by evaluating the ratio of nonsynonymous to synonymous fixations between species (dN/dS). Ratios above 1 indicate positive selection, ratios below 1 indicate purifying selection, and a dN/dS ratio of 1 implies strict neutrality [3,7]. Although some studies have ...
Nucleotide substitutions and evolution of duplicate genes.
Nucleotide substitutions and evolution of duplicate genes.

... aligning the underlying nucleotides, we look on each side of a gap for a region that begins with an anchor and in which two out of the seven amino acids (including the anchor) are an exact match. The probability of two out of seven random amino acids being the same is less than 5%. We then discard t ...
Evolution #12 Selection
Evolution #12 Selection

... genetically diverse offspring. There are several reasons for thinking this. One is that sexual reproduction is often associated with stress or environmental change, which is when variability would be most useful. Sexual reproduction is often associated with dispersal, and making it through an unfavo ...
Evolutionary Genomics of Fast Evolving Tunicates
Evolutionary Genomics of Fast Evolving Tunicates

... have undergone a similar, yet less extreme, process of genome compaction, gene density is between three (C. intestinalis) and four (C. savignyi) times lower than O. dioica (see table 1 for details on genome sizes and gene numbers). In turn, in comparison to nontunicate chordates, the difference is c ...
The evolutionary origins of inflammation
The evolutionary origins of inflammation

... beings   no   longer   live   in   an   environment   that   is   period  of  time,  has  therefore  been  put  to  the  test   optimally   suited   to   their   genes.   In   other   words:   extensively,   and,   as   a   result,   ha ...
Article Positive Selection Underlies Faster-Z
Article Positive Selection Underlies Faster-Z

... was in general detected for both males and females (fig. 5A). Consistent with the pairwise species comparisons in the gonad (fig. 3) we found higher expression divergence for genes on the Z than for autosomal genes in all six species comparisons in females, but not in males (fig. 6A). We calculated ...
Simple Sequence Repeats as Advantageous Mutators
Simple Sequence Repeats as Advantageous Mutators

... rodent species, while montane and meadow voles (M. montanus and M. pennsylvanicus) are asocial and non-monogamous. These differing social behaviors depend on the pattern of expression for the vasopressin receptor avpr1a gene, with higher levels of expression in the ventral forebrain of the social vo ...
Emergent Neutrality in Adaptive Asexual Evolution
Emergent Neutrality in Adaptive Asexual Evolution

... a—potentially large—fraction of genomic sites to have nearly random fixed alleles, which do not reflect the direction of selection at these sites. Thus, interference interactions not only reduce the speed of adaptation, but also degrade the genome state and the population’s fitness in its current envir ...
Phenotypic Evolution and Parthenogenesis Michael Lynch
Phenotypic Evolution and Parthenogenesis Michael Lynch

... Cenozoic suggests that Melanoides tuberculata, one of the few unisexual mollusks in existence today, has undergone evolutionary transitions just as dramatic as sexual species (Williamson 1981). Although theoretical work signals the potential importance of Muller's ratchet in haploid unisexual popula ...
The Birth- and- Death Evolution of Multigene Families Revisited
The Birth- and- Death Evolution of Multigene Families Revisited

... the origin of the family members is, in many cases, much more informative: not only does it explain the chromosomal distribution of family members, but it also provides insights into their evolutionary fate. Gene families essentially arise by 2 basic gene duplication mechanisms: unequal crossing-ove ...
Variation in a Population
Variation in a Population

... frequency of alleles that have a deleterious effect on the phenotype - that is, produce organisms of lower fitness. This process can continue until the allele is eliminated from the population. Purifying selection results in functional genetic features, such as protein-coding genes or regulatory seq ...
The evolutionary causes and consequences of sex
The evolutionary causes and consequences of sex

... Abstract | Females and males often differ extensively in their physical traits. This sexual dimorphism is largely caused by differences in gene expression. Recent advances in genomics, such as RNA sequencing (RNA-seq), have revealed the nature and extent of sex-biased gene expression in diverse spec ...
- Cypress HS
- Cypress HS

... Random mating ensures that each individual has an equal chance of passing on its alleles to offspring. In natural populations, mating is rarely completely random. Many species select mates based on particular heritable traits. ...
16-2 Evolution as Genetic Change
16-2 Evolution as Genetic Change

... Copyright Pearson Prentice Hall ...
An evolutionary relationship between genetic variation and
An evolutionary relationship between genetic variation and

... genetic variation, whereas the above recent study concerns evolution speed and intrinsic phenotypic fluctuations of clones. As both state the proportionality with the evolution speed, the question arises whether there should be some relationship between phenotypic variance by the distribution of gene ...
Oakley
Oakley

... the organism can generate replicated structures. Perhaps stemmata originated in this way. In these cases, the structure is duplicated in a morphological sense, but each individual structure is also the product of the same wavegenerating process. Fates of duplicated eyes Regardless of the mechanism, ...
Evolutionary significance of stress- induced mutagenesis in
Evolutionary significance of stress- induced mutagenesis in

... selective cost associated with the activity of error-free DNA repair systems. Therefore, there is no strong selective pressure to reduce the error-rate. Another example of molecular constraints leading to mutagenesis is RpoS-dependent induction of the dinB gene, which is specific to the stationary p ...
lactase persistence: evidence for selection
lactase persistence: evidence for selection

... There was strong selection pressure for the lactase-persistence allele. This selection caused the allele (and surrounding DNA) to be passed on from one generation to the next. Evidence for this selective sweep can be seen as a large area of homozygosity in all lactase-persistent individuals. Because ...
The emergence of individual species
The emergence of individual species

... influence in terms of distribution of molecules with universal functions, because if there was no HGT at all, the distribution of molecules should be solely depends on vertical inheritance, i.e. genealogy and that would lead to a simple tree instead of a reticulated tree in Figure 1b, which is not t ...
L20PositiveNegativeBalancing
L20PositiveNegativeBalancing

... factors, working together, affect genetic variation within populations. However, this theory is useful only if we know the actual parameters of factors of Microevolution. This can be accomplished either by direct measurements, for example of the mutation rate (by parentoffspring comparisons), or thr ...
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Adaptive evolution in the human genome

Adaptive evolution results from the propagation of advantageous mutations through positive selection. This is the modern synthesis of the process which Darwin and Wallace originally identified as the mechanism of evolution. However, in the last half century there has been considerable debate as to whether evolutionary changes at the molecular level are largely driven by natural selection or random genetic drift. Unsurprisingly, the forces which drive evolutionary changes in our own species’ lineage have been of particular interest. Quantifying adaptive evolution in the human genome gives insights into our own evolutionary history and helps to resolve this neutralist-selectionist debate. Identifying specific regions of the human genome that show evidence of adaptive evolution helps us find functionally significant genes, including genes important for human health, such as those associated with diseases.
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