The dog is an example of how selection can change the frequency of alleles inpopulation. Dog have been artificially selected for certain characteristics for manyyears and different breeds have different alleles.(a) What do you understand by the term artificial selection?(b) Which of the following statements is not true about micro-evolution?1(i) Changes are small even though they are significant.(ii) It properly explains how many new species come into existence.(in) It simply changes the common characteristics of a particular crecies.(iv) Two independent species can be evolved.(c) Write the term for the type of evolution being discussed in the example in thepassage.(d) What name would you give to the type of allele discussed in the abovepassage?3
Answers
Explanation:
The size, shape, and behavior of the modern domesticated dog has been sculpted by artificial selection for at least 14,000 years. The genetic substrates of selective breeding, however, remain largely unknown. Here, we describe a genome-wide scan for selection in 275 dogs from 10 phenotypically diverse breeds that were genotyped for over 21,000 autosomal SNPs. We identified 155 genomic regions that possess strong signatures of recent selection and contain candidate genes for phenotypes that vary most conspicuously among breeds, including size, coat color and texture, behavior, skeletal morphology, and physiology. In addition, we demonstrate a significant association between HAS2 and skin wrinkling in the Shar-Pei, and provide evidence that regulatory evolution has played a prominent role in the phenotypic diversification of modern dog breeds. Our results provide a first-generation map of selection in the dog, illustrate how such maps can rapidly inform the genetic basis of canine phenotypic variation, and provide a framework for delineating the mechanistic basis of how artificial selection promotes rapid and pronounced phenotypic evolution.
Keywords: Canis lupis, evolution
The modern domesticated dog (Canis lupus familiaris) represents one of the longest-running experiments in human history (1, 2). This experiment, still actively being conducted, has resulted in over 400 genetically distinct breeds that harbor considerable variation in behavioral, physiological, and morphological phenotypes (3). Although the domestication of dogs began over 14,000 years ago (4, 5), the spectacular phenotypic diversity exhibited among breeds is thought to have originated much more recently, largely through intense artificial selection and strict breeding practices to perpetuate desired characteristics. Thus, the canine genome, shaped by centuries of strong selection, likely contains many important lessons about the genetic architecture of phenotypic variation and the mechanistic basis of rapid short-term evolution. Indeed, dogs and other domesticated species played an important role in Darwin’s On the Origin of the Species (6), as they provide vivid examples of descent with modification. However, relatively little progress has been made on systematically identifying which regions of the canine genome have been influenced by selective breeding during the natural history of the dog.
Most studies of artificial selection in dogs have focused on single-gene analyses arising from phenotype-driven studies. Notable examples include IGF1 (7), an expressed FGF4 retrogene (8), and three genes (RSPO2, FGF5, and KRT71) (9) that influence variation in size, limb length, and coat phenotypes, respectively. However, candidate gene approaches are not well suited to providing general insights into the frequency, location, and types of loci influenced by selection. Furthermore, disentangling the confounding effects of selection and demographic history on patterns of DNA sequence variation is notoriously difficult with single-locus analyses (10). To date, the only genome-wide analysis of selection in dogs has focused on a specific phenotype in a single breed, foreshortened limbs in Dachshunds, using a relatively coarse panel of microsatellite markers (11).
Recent advances in canine genomics, including a high-quality reference sequence (12), the construction of a dense map of over 2.5 million SNPs (12), and the development of SNP genotyping arrays (13) have enabled systematic studies of canine genomic variation. Using these genomic resources, we performed the largest genome-wide scan to date for targets of selection in purebred dogs. By applying unique statistical methods to a map of over 21,000 SNPs genotyped in a phenotypically diverse panel of 10 breeds, we identified 155 regions of the canine genome that have likely been subject to strong artificial selection. Our results are unique in providing a detailed glimpse into the genetic legacy of centuries of breeding practices, suggest that regulatory evolution has played a prominent role in the rapid phenotypic diversification of breeds, and nominate numerous candidate genes for contributing to breed-specific differences in behavior, morphology, and physiology.
b) Two independent species can be evolved due to micro evolution is false.
c) Artificial selection
d) genetic drift
Explanation:
The artificial selection in the breeding of organisms to yield specific phenotypic traits. The two animals with beneficial or specific traits are bred to produce the phenotype trait in the offspring. The process is done by selecting the desired animal with desired trait to be bred.
Two independent species cannot evolve due to micro evolution. The change in frequency of alleles over a time in a population of single species is microevolution
Genetic drift occurs due to random mating in the population causing change in allele frequencies of existing genes. This occurs due to sampling error. The effects are seen mainly in small population. It may result in loss of some benificial genes.
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