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- https://bio.libretexts.org/Courses/Clackamas_Community_College/Clackamas_Biology_112_OER_Textbook_(OpenStax)/08%3A_Molecular_Biology/8.02%3A_DNA_ReplicationWhen a cell divides, it is important that each daughter cell receives an identical copy of the DNA. This is accomplished by the process of DNA replication. The replication of DNA occurs during the syn...When a cell divides, it is important that each daughter cell receives an identical copy of the DNA. This is accomplished by the process of DNA replication. The replication of DNA occurs during the synthesis phase, or S phase, of the cell cycle, before the cell enters mitosis or meiosis.
- https://bio.libretexts.org/Courses/North_Central_State_College/BIOL_1550%3A_Microbiology_(2025)/14%3A_Horizontal_Gene_Transfer_and_Operons/14.01%3A_MutationsA mutation is a heritable change in the DNA sequence of an organism. The resulting organism, called a mutant, may have a recognizable change in phenotype compared to the wild type, which is the phenot...A mutation is a heritable change in the DNA sequence of an organism. The resulting organism, called a mutant, may have a recognizable change in phenotype compared to the wild type, which is the phenotype most commonly observed in nature. A change in the DNA sequence is conferred to mRNA through transcription, and may lead to an altered amino acid sequence in a protein on translation.
- https://bio.libretexts.org/Courses/Citrus_College/Citrus_College_General_Biology_Textbook/13%3A_Evolution_and_Natural_Selection/13.02%3A_Discovering_How_Populations_ChangeEvolution by natural selection arises from three conditions: individuals within a species vary, some of those variations are heritable, and organisms have more offspring than resources can support. Th...Evolution by natural selection arises from three conditions: individuals within a species vary, some of those variations are heritable, and organisms have more offspring than resources can support. The consequence is that individuals with relatively advantageous variations will be more likely to survive and have higher reproductive rates than those individuals with different traits. The advantageous traits will be passed on to offspring in greater proportion.
- https://bio.libretexts.org/Courses/Citrus_College/Citrus_College_General_Biology_Textbook/13%3A_Evolution_and_Natural_Selection/13.04%3A_Mechanisms_of_EvolutionFour factors that can change the allele frequencies of a population. Natural selection works by selecting for alleles that confer beneficial traits or behaviors, while selecting against those for dele...Four factors that can change the allele frequencies of a population. Natural selection works by selecting for alleles that confer beneficial traits or behaviors, while selecting against those for deleterious qualities. Mutations introduce new alleles into a population. Genetic drift stems from the chance occurrence that some individuals have more offspring than others and results in changes in allele frequencies that are random in direction.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Principles_of_Biology/03%3A_Chapter_3/22%3A_Evolution_in_Action/22.02%3A_Population_GeneticsBy chance, some individuals will have more offspring than others—not due to an advantage conferred by some genetically-encoded trait, but just because one male happened to be in the right place at the...By chance, some individuals will have more offspring than others—not due to an advantage conferred by some genetically-encoded trait, but just because one male happened to be in the right place at the right time (when the receptive female walked by) or because the other one happened to be in the wrong place at the wrong time (when a fox was hunting).
- https://bio.libretexts.org/Courses/Gettysburg_College/01%3A_Ecology_for_All/07%3A_Phylogenies_and_the_History_of_Life/7.04%3A_Perspectives_on_the_Phylogenetic_TreeThe concepts of phylogenetic modeling are constantly changing. It is one of the most dynamic fields of study in all of biology. Over the last several decades, new research has challenged scientists’ i...The concepts of phylogenetic modeling are constantly changing. It is one of the most dynamic fields of study in all of biology. Over the last several decades, new research has challenged scientists’ ideas about how organisms are related. New models of these relationships have been proposed for consideration by the scientific community.
- https://bio.libretexts.org/Courses/Gettysburg_College/01%3A_Ecology_for_All/06%3A_The_Evolution_of_Populations_and_Species/6.04%3A_Population_GeneticsIndividuals of a population often display different phenotypes, or express different alleles of a particular gene, referred to as polymorphisms. Populations with two or more variations of particular c...Individuals of a population often display different phenotypes, or express different alleles of a particular gene, referred to as polymorphisms. Populations with two or more variations of particular characteristics are called polymorphic. The distribution of phenotypes among individuals, known as the population variation, is influenced by a number of factors, including the population’s genetic structure and the environment.
- https://bio.libretexts.org/Courses/Gettysburg_College/01%3A_Ecology_for_All/06%3A_The_Evolution_of_Populations_and_Species/6.03%3A_The_Hardy-Weinberg_EquilibriumThe Hardy-Weinberg law argues that the gene frequencies and genotype ratios in a randomly-breeding population remain constant from generation to generation. Evolution involves changes in the gene poo...The Hardy-Weinberg law argues that the gene frequencies and genotype ratios in a randomly-breeding population remain constant from generation to generation. Evolution involves changes in the gene pool, while a population in Hardy-Weinberg equilibrium shows no change. Hence, populations are able to maintain a reservoir of variability so that if future conditions require it, the gene pool can change.
- https://bio.libretexts.org/Courses/Gettysburg_College/01%3A_Ecology_for_All/07%3A_Phylogenies_and_the_History_of_Life/7.03%3A_Determining_Evolutionary_RelationshipsScientists must collect accurate information that allows them to make evolutionary connections among organisms. Similar to detective work, scientists must use evidence to uncover the facts. In the cas...Scientists must collect accurate information that allows them to make evolutionary connections among organisms. Similar to detective work, scientists must use evidence to uncover the facts. In the case of phylogeny, evolutionary investigations focus on two types of evidence: morphologic (form and function) and genetic.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/10%3A_Mutation/10.01%3A_Mutations_-_Causes_and_SignificanceThis page discusses DNA mutations in living cells, their types (point mutations, indels, etc.), and diseases associated with them, like sickle cell anemia. It highlights the role of mutations in evolu...This page discusses DNA mutations in living cells, their types (point mutations, indels, etc.), and diseases associated with them, like sickle cell anemia. It highlights the role of mutations in evolution, gene duplication, and translocations, along with their rarity and varying rates across species. Specifically, C. elegans has a mutation rate of approximately 2.1 x 10^-8 per base pair per generation, with males contributing more due to mitotic divisions.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/11%3A_Genomics/11.09%3A_Genetic_Screening_for_PhenylketonuriaThis page discusses Phenylketonuria (PKU), a genetic disorder resulting from defective genes affecting phenylalanine hydroxylase, leading to harmful phenylalanine buildup. Early diagnosis through bloo...This page discusses Phenylketonuria (PKU), a genetic disorder resulting from defective genes affecting phenylalanine hydroxylase, leading to harmful phenylalanine buildup. Early diagnosis through blood tests is crucial, and genetic screening can assess parental transmission risk. Despite available treatments, testing can be complicated by false negatives. PKU is a recessive trait, but the phenylalanine tolerance test complicates its dominance classification.
