Why are dominant traits not always common

Any alleles of the nearby genes that are on the same chromosome as the beneficial allele of the gene undergoing selection will also be selected for, so recessive alleles can increase in frequency this way.ДЈ) While it's simple to get rid of individuals with two copies of a recessive allele (especially if they have lowered fitness as a result), it's tricky to identify the individuals carrying recessive alleles that don't impact phenotype.

This means that selection for an allele of a gene that impacts fitness can result in selection for certain alleles of the nearby genes as well. Genes that are located near each other are linked, meaning that inheriting the allele on chromosome 1 for one gene makes it likely you'll also inherit the allele on chromosome 1 for any nearby genes. It's also commonly referred to as 'hybrid vigor,' which gets at the idea that it's often beneficial to merge the traits from two very different parents so that their offspring can tolerate or react to a wider range of environments.Дў) The placement of genes on chromosomes influences how they are inherited. Geneticists describe this as 'overdominance,' meaning that the individuals with one dominant and one recessive allele actually have a more extreme phenotype than individuals with two dominant alleles. Having two recessive alleles means you have the sickle-cell phenotype and the health problems that go with it. This doesn't always mean that the recessive phenotype is beneficial - for example, having one recessive allele for the sickle-cell gene causes individuals to be resistant to malaria, increasing fitness of heterozygotes in environments where malaria is common. That said, there are many things that keep recessive alleles present in populations:ДЎ) Some recessive alleles are beneficial (they increase the fitness of individuals who carry them). Genes cannot be dominant or recessive, alleles are dominant or recessive. We make our world significant by the courage of our questions and by the depth of our answers. For more open-ended questions, try /r/AskScienceDiscussion | Sign up to be a panelist!.Looking for flair? Sign up to be a panelist!.Richard Johnson, Nature Wants Us To Be FatДЄskScience AMA Series: Deep Brain Stimulation for OCDДЄsk Anything Wednesday - Engineering, Mathematics, Computer scienceДЄsk Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, PsychologyДЄsk Anything Wednesday - Economics, Political Science, Linguistics, Anthropology Neuroscience, Neurology, Neurochemistry, Cognitive NeuroscienceДЄskScience AMA Series: Diagnostics, American Society for MicrobiologyДЄsk Anything Wednesday - Physics, Astronomy, Earth and Planetary ScienceДЄskScience AMA Series: Dr. Medicine, Oncology, Dentistry, Physiology, Epidemiology, Infectious Disease, Pharmacy, Human Body Psychology, Cognitive Psychology, Developmental Psychology, Abnormal, Social Psychology Social Science, Political Science, Economics, Archaeology, Anthropology, LinguisticsД«iology, Evolution, Morphology, Ecology, Synthetic Biology, Microbiology, Cellular Biology, Molecular Biology, Paleontology

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Why are dominant traits not always common