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Inbreeding Depression
Inbreeding depression is the reduced biological fitness caused by loss of genetic diversity as a consequence of inbreeding, the breeding of individuals closely related genetically. This loss of genetic diversity results from small population size, often stemming from a population bottleneck. Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. In general, the higher the genetic variation or gene pool within a breeding population, the less likely it is to suffer from inbreeding depression, though inbreeding and outbreeding depression can simultaneously occur. Inbreeding depression seems to be present in most populations of organisms, but varies across mating systems. Remarkably, hermaphroditic species often exhibit lower degrees of inbreeding depression than outcrossing species, as repeated generations of selfing is thought to purge deleterious alleles from populations. For example, the outcrossing nematode (roundworm) '' Caen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inbreeding Depression In Delphinium Nelsonii
Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and other consequences that may arise from expression of deleterious recessive traits resulting from incestuous sexual relationships and consanguinity. Animals avoid inbreeding only rarely. Inbreeding results in homozygosity which can increase the chances of offspring being affected by recessive traits. In extreme cases, this usually leads to at least temporarily decreased biological fitness of a population (called inbreeding depression), which is its ability to survive and reproduce. An individual who inherits such deleterious traits is colloquially referred to as ''inbred''. The avoidance of expression of such deleterious recessive alleles caused by inbreeding, via inbreeding avoidance mechanisms, is the main selective reason for outcrossi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shetland Pony Inbred
Shetland (until 1975 spelled Zetland), also called the Shetland Islands, is an archipelago in Scotland lying between Orkney, the Faroe Islands, and Norway, marking the northernmost region of the United Kingdom. The islands lie about to the northeast of Orkney, from mainland Scotland and west of Norway. They form part of the border between the Atlantic Ocean to the west and the North Sea to the east. The island's area is and the population totalled in . The islands comprise the Shetland (Scottish Parliament constituency), Shetland constituency of the Scottish Parliament. The islands' administrative centre, largest settlement and only burgh is Lerwick, which has been the capital of Shetland since 1708, before which time the capital was Scalloway. Due to its location it is accessible only by ferry or flight with an airport located in Sumburgh as well as a port and emergency airstrip in Lerwick. The archipelago has an oceanic climate, complex geology, rugged coastline, and m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological properties, and its behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code (its genotype) and the influence of environmental factors. Both factors may interact, further affecting the phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black, and brown. Richard Dawkins in 1978 and again in his 1982 book '' The Extended Phenotype'' suggested that one can regard bird nests and other built structures such as caddisfly larva cases and beaver dams ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
De Novo Mutation
A de novo mutation (DNM) is any mutation or alteration in the genome of an individual organism (human, animal, plant, microbe, etc.) that was not inherited from its parents. This type of mutation spontaneously occurs during the process of DNA replication during cell division. De novo mutations, by definition, are present in the affected individual but absent from both biological parents' genomes. A de novo mutation can arise in a sperm or egg cell and become a germline mutation, or after fertilization as a post-zygotic mutation that cannot be inherited by offspring. These mutations can occur in any cell of the offspring, but those in the germ line (eggs or sperm) can be passed on to the next generation. In most cases, such a mutation has little or no effect on the affected organism due to the redundancy and robustness of the genetic code. However, in rare cases, it can have notable and serious effects on overall health, physical appearance, and other traits. Disorders that most co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with selective breeding, artificial selection, which is intentional, whereas natural selection is not. Genetic diversity, Variation of traits, both Genotype, genotypic and phenotypic, exists within all populations of organisms. However, some traits are more likely to facilitate survival and reproductive success. Thus, these traits are passed the next generation. These traits can also become more Allele frequency, common within a population if the environment that favours these traits remains fixed. If new traits become more favoured due to changes in a specific Ecological niche, niche, microevolution occurs. If new traits become more favoured due to changes in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purebred
Purebreds are cultivars of an animal species achieved through the process of selective breeding. When the lineage of a purebred animal is recorded, that animal is said to be pedigreed. Purebreds breed true-to-type, which means the progeny of like-to-like purebred parents will carry the same phenotype, or observable characteristics of the parents. A group of like purebreds is called a pure-breeding line or strain. True breeding In the world of selective animal breeding, to "breed true" means that specimens of an animal breed will breed true-to-type when mated like-to-like; that is, that the progeny of any two individuals of the same breed will show fairly consistent, replicable and predictable characteristics, or traits with sufficiently high heritability. A puppy from two purebred dogs of the same breed, for example, will exhibit the traits of its parents, and not the traits of all breeds in the subject breed's ancestry. Breeding from too small a gene pool, especially direct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Livestock
Livestock are the Domestication, domesticated animals that are raised in an Agriculture, agricultural setting to provide labour and produce diversified products for consumption such as meat, Egg as food, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animals which are raised for consumption, and sometimes used to refer solely to farmed ruminants, such as cattle, sheep, and goats. The breeding, maintenance, slaughter and general subjugation of livestock called ''animal husbandry'', is a part of modern agriculture and has been practiced in many cultures since humanity's transition to farming from hunter-gatherer lifestyles. Animal husbandry practices have varied widely across cultures and periods. It continues to play a major economic and cultural role in numerous communities. Livestock farming practices have largely shifted to intensive animal farming. Intensive animal farming increases the yield of the various commercial outputs, but also nega ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hybrid Vigour
Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. The heterotic offspring often has traits that are more than the simple addition of the parents' traits, and can be explained by Mendelian or non-Mendelian inheritance. Typical heterotic/hybrid traits of interest in agriculture are higher yield, quicker maturity, stability, drought tolerance etc. Definitions In proposing the term heterosis to replace the older term heterozygosis, G.H. Shull aimed to avoid limiting the term to the effects that can be explained by heterozygosity in Mendelian inheritance. Heterosis is often discussed as the opposite of inbreeding depression, although differences in these two concepts can be seen in evolutionary considerations such as the role of genetic variation or the effects of genetic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overdominance
Overdominance is a phenomenon in genetics where the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents. Overdominance can also be described as heterozygote advantage regulated by a single genomic locus, wherein heterozygous individuals have a higher fitness than homozygous individuals. However, not all cases of the heterozygote advantage are considered overdominance, as they may be regulated by multiple genomic regions. Overdominance has been hypothesized as an underlying cause for heterosis (increased fitness of hybrid offspring). Examples Sickle cell anemia An example of overdominance in humans is that of the sickle cell anemia. This condition is determined by a single polymorphism. Possessors of the deleterious allele have lower life expectancy, with homozygotes rarely reaching 50 years of age. However, this allele also yields some resistance to malaria. Thus in regions where malaria exerts or has exerted a strong selectiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sterility (physiology)
Sterility is the physiological inability to effect sexual reproduction in a living thing, members of whose kind have been produced sexually. Sterility has a wide range of causes. It may be an inherited trait, as in the mule; or it may be acquired from the environment, for example through physical injury or disease, or by exposure to radiation. Sterility is the inability to produce a biological child, while infertility is the inability to conceive after a certain period. Sterility is rarely discussed in clinical literature and is often used synonymously with infertility. Infertility affects about 12-15% of couples globally. Still, the prevalence of sterility remains unknown. Sterility can be divided into three subtypes natural, clinical, and hardship. Natural sterility is the couple's physiological inability to conceive a child. Clinical sterility is natural sterility for which treatment of the patient will not result in conception. Hardship sterility is the inability to take adv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterozygous
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Most eukaryotes have two matching sets of chromosomes; that is, they are diploid. Diploid organisms have the same locus (genetics), loci on each of their two sets of homologous chromosomes except that the sequences at these loci may differ between the two chromosomes in a matching pair and that a few chromosomes may be mismatched as part of a chromosomal Sex-determination system#Chromosomal determination, sex-determination system. If both alleles of a diploid organism are the same, the organism is #Homozygous, homozygous at that locus. If they are different, the organism is #Heterozygous, heterozygous at that locus. If one allele is missing, it is #Hemizygous, hemizygous, and, if both alleles are missing, it is #Nullizygous, nullizygous. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of Gene product, RNA or protein from a gene), DNA is first transcription (biology), copied into RNA. RNA can be non-coding RNA, directly functional or be the intermediate protein biosynthesis, template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of the population (biology), population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
