Lecture 2: Population Genetics PDF

Lecture 2: Population Genetics ha Dr. Hadil Alahdal preencoded.png Explore the foundational concepts of evolutionary genetics, from the mechanisms of genetic variation to the forces that shape allele frequencies. Learn how these principles drive the adaptation and di...

Lecture 2: Population Genetics ha Dr. Hadil Alahdal preencoded.png Explore the foundational concepts of evolutionary genetics, from the mechanisms of genetic variation to the forces that shape allele frequencies. Learn how these principles drive the adaptation and diversification of species over time. Lectures outline G en etic Variatio n M echanism s that g enerate g enetic divers ity within a pop ulatio n, including reco m bination, a nd g ene flow. A llele Freq uen cies H ow allele frequencies cha ng e over tim e due to evolutionary fo rces like m ig ratio n. H ard y - W ein b erg Eq u ilib riu m The m athem atica l m odel that describ es the expected g eno typ ic and allelic po pulation under certa in as sum ptions. Ev olutio n ar y Fo rc es The key drivers of evolution, includ ing natural selection, g enetic drift, and g ene how they im p act g enetic diversity. A d ap tatio n and F itnes s H ow g enetic variatio n enab les org anism s to ad apt to their environm ent, a nd reproductive fitness. S p eciatio n The processes by which new species a rise, includ ing g eog ra phic isolation, ba rriers, and ada ptive rad iation. C o n ser vatio n G enetic s H ow evolutionary g enetics p rincip les are ap plied to conserve g enetic diversity endang ered species. The Wolves of Isle Royale P: 1149 file:///C:/Users/al_ma/Download s/Genetics%20A%20Conceptual%2 0Approach%20by%20Pierce,%20Be njamin%20A.%20(z- lib.org)%20(1).pdf Conservation Genetics Preserving Genetic Diversity Ensuring Species Survival Genetic Analysis Conservation genetics focuses on Strategies are employed to protect genetic Advanced genetic analysis techniques are maintaining healthy gene pools and genetic diversity and avoid the harmful techniques are used to monitor preventing the loss of genetic variation harmful effects of inbreeding, allowing populations and guide conservation within endangered populations. allowing endangered species to thrive. efforts to preserve critical genetic thrive. diversity. preencoded.png Conservation Genetics Conservation genetics uses genetic information to guide conservation efforts for endangered or threatened species. Genetic Monitoring Population Management Tracking genetic diversity over time. Designing strategies for species recovery. Habitat Connectivity Evolutionary Adaptation Maintaining gene flow between Understanding how species adapt to populations. environmental change. preencoded.png Genotypic and Allelic Frequencies Are Used to Describe the Gene Pool of a Population Population genetics is a field of study that focuses on the genetic makeup of populations and how it changes over time. The genetic makeup of a population, known as its gene pool, is represented by the frequencies of genotypes and alleles. Population Genetics: Uncovering Genetic Variation Understanding Genetic Variation Fundamental for Research Population genetics studies how genetic variation changes within and This field is fundamental for understanding evolution, conservation, between populations over time. and human health. preencoded.png Inbreeding Inbreeding is the mating of closely related individuals. It can lead to a decrease in genetic diversity and an increase in the frequency of harmful recessive alleles. Reduced Fitness Increased Genetic Load Increased vulnerability to Accumulation of harmful diseases and environmental recessive alleles. stresses. Inbreeding Depression Reduced fertility, survival, and overall fitness. preencoded.png Mutation: The Driving Force of Genetic Diversity Spontaneous Mutations Induced Mutations Beneficial Mutations Unintended changes in the DNA sequence External factors like radiation or chemicals Mutations that improve an organism's that occur naturally during replication, can disrupt DNA replication, leading to chances of survival and reproduction, introducing new genetic variation. errors and genetic changes. providing the raw material for evolution. preencoded.png Mutation: The Driving Force of Genetic Diversity 2 Deleterious Mutations Neutral Mutations Genetic changes that reduce an organism's fitness and overall well-being, DNA changes that neither improve nor reduce an organism's fitness, but often targeted by natural selection. are important for tracing evolutionary history. preencoded.png Gene Flow Gene flow is the movement of genes between populations. It can increase genetic diversity and prevent populations from becoming isolated. Migration Movement of individuals between populations. Interbreeding Introduction of new alleles and mixing of gene pools. Reduced Genetic Drift Counteracts the effects of random allele frequency changes. Increased Adaptation Promotes the spread of advantageous alleles. preencoded.png Evolutionary Biology: Speciation The Process of Speciation Mechanisms of Speciation Importance for Biodiversity Speciation is the process by which new Speciation can occur through a variety of The study of speciation is crucial for species arise, often through the mechanisms, such as geographic isolation, understanding the origins of biodiversity development of reproductive barriers that adaptation to different environments, or and the evolutionary trajectories of lead to the divergence of populations over the emergence of genetic different lineages. time. incompatibilities. preencoded.png Allele Frequencies Allele Frequencies: A Numerical From 0 to 1 Dynamic Frequencies Representation Allele frequencies are represented as Allele frequencies change over time, The frequency of an allele is its proportion decimals, ranging from 0 to 1. An allele driven by factors such as mutation, gene within the gene pool. frequency of 0 indicates the allele is not flow, and genetic drift. present in the population, while a frequency of 1 means all individuals carry that allele. preencoded.png The Hardy–Weinberg Law Describes the Effect of Reproduction on Genotypic and Allelic Frequencies The primary goal of population genetics is to understand the processes that shape a population’s gene pool. 1- we must ask what effects reproduction and Mendelian principles have on the genotypic and allelic frequencies. 2- How do the segregation of alleles in gamete formation and the combining of alleles in fertilization influence the gene pool? The answer to this question lies in the Hardy–Weinberg law,among the most important principles of population genetics. preencoded.png The Hardy–Weinberg Law preencoded.png Hardy-Weinberg Assumption First, it assumes that the population is large. second assumption of the Hardy–Weinberg law is that members of the population mate randomly with respect to genotype, The third assumption of the Hardy–Weinberg law is that the allelic frequencies of the population are not affected by natural selection, migration, or mutation. A final point is that the assumptions of the Hardy–Weinberg law apply to a single locus preencoded.png Example: If there are only 2 alleles at a locus and the dominant is at frequency 0.3, what is the frequency of heterozygotes and how do you figure it out? you can figure it out by making use of the Hardy-Weinburg equation which is p+q=1. let’s say p is the frequency of 0.3 and we are looking for the frequency of q. p+q=1 0.3+q=1 q= 0.7 or 70% Concept check Which statement is not true about Hardy-Weinberg law: a- The allelic frequencies of (p and q) are equal b- The population is large. c-The members of the population mate randomly with respect to genotype, d-The allelic frequencies of the population are not affected by natural selection preencoded.png Genetic Diversity Genetic diversity refers to the variation in genes within a population. It is crucial for a population's adaptability and resilience to environmental changes. 1 Adaptability 2 Resilience High genetic diversity allows Genetic diversity safeguards populations to adapt to against the risk of extinction changing environments and caused by disease, climate survive threats. change, or other disturbances. 3 Evolution 4 Conservation Genetic variation is the raw Protecting genetic diversity is material for evolutionary essential for preserving change. biodiversity and ensuring the long-term health of ecosystems. preencoded.png Factors Affecting Genetic Diversity Genetic Drift Gene Flow Natural Selection Random fluctuations in allele frequencies, The movement of individuals between Differential survival and reproduction especially in smaller populations, can lead populations introduces new alleles and based on traits influenced by genes. It to changes in the genetic makeup over alters the allele frequencies, increasing favors advantageous alleles and eliminates time. genetic diversity. disadvantageous ones, shaping the genetic diversity of a population. preencoded.png Genetic Drift Genetic drift is the random fluctuation of allele frequencies within a population over successive generations. This process is especially significant in smaller populations, where the effects of chance events can have a more pronounced impact on the genetic makeup of the group. 1 Founder Effect A new population is established by a small group of individuals from a larger population. This can lead to a loss of genetic diversity, as the random sampling of alleles from the original population may not be representative of the full diversity present. Over time, the founder population can diverge significantly from the source population due to this random sampling effect. 2 Bottleneck Effect A drastic reduction in population size due to a catastrophic event, such as a natural disaster, disease outbreak, or human-caused environmental degradation. The surviving population may have a limited gene pool, leading to a loss of genetic diversity. This can make the population more vulnerable to future threats and reduce its ability to adapt to changing conditions. preencoded.png The Effects of Genetic Drift Genetic drift is a random process that can have significant effects on the genetic makeup of a population over time. The key effects of genetic drift: 1 A change in allelic frequencies 2 Reduced of genetic variation within a population. (Fixation) 3 Different population diverge genetically with time The first two factors tack place within population, and the third is between populations preencoded.png Genetic Drift Genetic drift is a random process that can have significant effects on the genetic makeup of a population over time. It occurs due to the random sampling of alleles during reproduction, which can lead to changes in allele frequencies from one generation to the next. Genetic drift can also occur between different populations of the same species. When populations become isolated from one another, random changes in allele frequencies can lead to those populations diverging genetically over time. This is known as interpopulation genetic drift. preencoded.png Several evolutionary forces can cause changes in allelic frequencies Natural Selection Natural selection is the process by which individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to future generations. This drives the adaptation of species over time. Natural selection acts on the phenotypes of individuals - the observable physical and behavioral characteristics that result from the interaction of an organism's genotype and its environment. Individuals with phenotypes that are better adapted to their environment will have a higher fitness, meaning they are more likely to survive and reproduce. This in turn leads to an increase in the frequency of the corresponding genotypes in the population over time. summary: These evolutionary forces affect both genetic variation within populations and genetic divergence between populations. Evolutionary forces that increase genetic variation within populations are listed. These forces include some types of natural selection, such as overdominance, in which both alleles are favored. Mutation and migration also increase genetic variation within populations, because they introduce new alleles into the population. Evolutionary forces that decrease genetic variation within populations are listed in the lower left quadrant. These forces include genetic drift, which decreases variation through the fixation of alleles, and some forms of natural selection, such as directional selection. preencoded.png References https://www.khanacademy.org/science/ap-biology/natural-selection/hardy- weinberg-equilibrium/v/allele-frequency https://www.biologyonline.com/dictionary/genetic-diversity