Introduction to Genetics and Evolution

Genotype refers to the genetic makeup of an organism, while phenotype is the expressed traits resulting from that genotype. Natural selection acts on phenotypes, influencing their reproductive success, which can change allele frequencies in a population.

Stabilizing selection promotes average traits and eliminates extremes, leading to reduced trait variation. An example is the optimal human birth weight of 3-4 kg, where weights outside this range are associated with higher risks of complications.

Directional selection favors one extreme trait, leading to gradual changes in that trait over time. For instance, lighter skin became advantageous for vitamin D production in populations migrating to areas with less sunlight.

<p>Gene flow occurs when individuals migrate and breed in new locations, introducing new alleles into the gene pool. This can increase genetic diversity and alter allele frequencies, potentially enhancing evolutionary change.</p> Signup and view all the answers

<p>Genetic drift is the random change in allele frequencies, especially in small populations, which can lead to decreased genetic diversity. It may result in the loss of advantageous alleles and fixation of harmful ones.</p> Signup and view all the answers

<p>The founder effect occurs when a small group colonizes a new area, leading to a limited gene pool that defines the new population. This can decrease genetic diversity and increase the likelihood of inbreeding and genetic disorders.</p> Signup and view all the answers

<p>Environmental factors affect reproductive success by favoring certain traits that enhance survival. These changes in trait fitness can lead to shifts in allele frequencies, driving evolutionary changes in populations.</p> Signup and view all the answers

<p>Natural selection can lead to speciation by promoting the divergence of traits in populations subjected to different environmental pressures, ultimately resulting in reproductive isolation. This divergence can lead to the formation of new species over time.</p> Signup and view all the answers

<p>The genotype refers to the genetic makeup of an organism, while the phenotype is the observable characteristics resulting from that genotype.</p> Signup and view all the answers

<p>Stabilizing selection favors intermediate phenotypes and reduces phenotypic variation.</p> Signup and view all the answers

<p>Directional selection causes the population's traits to shift towards one extreme of a trait spectrum.</p> Signup and view all the answers

<p>Disruptive selection favors individuals at both extremes of a trait spectrum, increasing phenotypic variation.</p> Signup and view all the answers

<p>Gregor Mendel established foundational principles of inheritance through his experiments with pea plants, demonstrating how traits are passed from parents to offspring.</p> Signup and view all the answers

<p>The four main mechanisms of natural selection are overproduction, competition, variation, and survival of the fittest.</p> Signup and view all the answers

<p>'Descent with modification' refers to the gradual change in populations over time, leading to the development of new species from common ancestors.</p> Signup and view all the answers

<p>Speciation is the evolutionary process through which new biological species arise, important because it contributes to biodiversity and the adaptation of organisms.</p> Signup and view all the answers

<p>Phenotype refers to the physical expression of a trait, while genotype refers to the genetic constitution of an individual.</p> Signup and view all the answers

<p>Disruptive selection favors individuals at both extremes of a trait distribution; for example, small-billed and large-billed birds thrive while medium-billed birds struggle to survive.</p> Signup and view all the answers

<p>Stabilizing selection favors intermediate phenotypes, reducing variation, whereas disruptive selection favors extreme phenotypes, leading to increased variation.</p> Signup and view all the answers

<p>Gregor Mendel is known as the father of modern genetics for his experiments with garden peas, which established the fundamental laws of inheritance.</p> Signup and view all the answers

<p>Speciation is the process by which new species are formed; it can occur through reproductive isolation due to geographic barriers.</p> Signup and view all the answers

<p>An allele is a version of a gene, with dominant alleles expressing the trait over recessive alleles, which are masked in the presence of a dominant partner.</p> Signup and view all the answers

<p>The filial generation (F1) represents the offspring of the parental generation (P), demonstrating how traits are inherited from one generation to the next.</p> Signup and view all the answers

<p>Homozygotes have identical alleles for a trait, while heterozygotes have two different alleles, influencing the trait's expression and inheritance.</p> Signup and view all the answers

<p>They discovered sperm and ova, highlighting that both males and females contribute to inheritance.</p> Signup and view all the answers

<p>Mendel's work provided genetic insight that Darwin's theory of evolution by natural selection lacked.</p> Signup and view all the answers

<p>'Survival of the Fittest' refers to individuals with advantageous traits being more likely to survive and reproduce.</p> Signup and view all the answers

<p>Adaptation refers to inherited traits that enhance an organism's survival and reproductive success.</p> Signup and view all the answers

<p>The chromosome theory explains that genes on chromosomes dictate inherited traits, linking genetics to evolution.</p> Signup and view all the answers

<p>'Descent with modification' refers to the gradual changes in species over time, leading to new species from common ancestors.</p> Signup and view all the answers

<p>Competition leads to the survival of individuals with advantageous traits, driving evolutionary change.</p> Signup and view all the answers

<p>Phenotypic variation provides the raw material for natural selection, allowing advantageous traits to be favored.</p> Signup and view all the answers

<p>Higher fitness increases the likelihood of passing genes to future generations, thereby altering allele frequency.</p> Signup and view all the answers

<p>A population bottleneck can significantly reduce genetic diversity by limiting the number of individuals contributing to the gene pool.</p> Signup and view all the answers

<p>Gene flow introduces new alleles into the gene pool, which can change allele frequencies within the population.</p> Signup and view all the answers

<p>Stabilizing selection favors intermediate traits, reducing the prevalence of extremes and keeping the population centered around an optimal trait value.</p> Signup and view all the answers

<p>The founder effect occurs when a small group colonizes a new area, leading to reduced genetic variation due to a limited allele pool.</p> Signup and view all the answers

<p>Directional selection has favored lighter skin in populations migrating to areas with lower sunlight, enhancing vitamin D production.</p> Signup and view all the answers

<p>Genetic drift can lead to the loss of genetic diversity and fixation of harmful alleles, impacting the overall adaptability of small populations.</p> Signup and view all the answers

<p>Environmental factors influence reproductive success, determining which traits are favored or selected against in a population.</p> Signup and view all the answers

<p>Disruptive selection favors individuals at both extremes of a trait, like small-billed and large-billed birds, resulting in reduced survival for intermediate phenotypes.</p> Signup and view all the answers

<p>Darwin lacked a scientific understanding of the mechanism of inheritance, which left his theory susceptible to critique.</p> Signup and view all the answers

<p>Geographical isolation prevents gene flow between populations, allowing for different traits to become dominant and leading to the formation of new species.</p> Signup and view all the answers

<p>Homozygotes have two identical alleles for a trait, while heterozygotes carry one dominant and one recessive allele.</p> Signup and view all the answers

<p>Mendel's experiments established fundamental laws of inheritance by demonstrating how traits are passed through discrete units, now known as genes.</p> Signup and view all the answers

<p>Mendel used manual techniques such as removing male parts and hand pollination.</p> Signup and view all the answers

<p>Alleles are different versions of a gene, and a dominant allele will express its trait over a recessive allele, which is masked in its presence.</p> Signup and view all the answers

<p>Mendel's study of filial generations, notably F1 and F2, revealed predictable patterns of inheritance that are central to genetic theory.</p> Signup and view all the answers

<p>The expected phenotypic ratio is 3:1, with three exhibiting the dominant trait and one the recessive trait.</p> Signup and view all the answers

<p>The locus is the specific location of a gene on a chromosome, essential for identifying alleles and understanding genetic variation.</p> Signup and view all the answers

<p>Mendel focused on binary traits, ensuring that traits were inherited similarly in both sexes, which simplified his observations.</p> Signup and view all the answers

<p>The Principle of Dominance states that in a pair of alleles, one can mask the expression of the other.</p> Signup and view all the answers

<p>Mendel's experiments laid the groundwork for the laws of inheritance and the concepts of dominant and recessive traits.</p> Signup and view all the answers

<p>All offspring will be heterozygous (Aa), showing the dominant phenotype.</p> Signup and view all the answers

<p>Pollination is the transfer of pollen from the male parts to the female parts of a flower, essential for fertilization.</p> Signup and view all the answers

<p>All offspring will be homozygous recessive (aa).</p> Signup and view all the answers

<p>It states that during gamete formation, the two alleles for a trait separate so that each gamete receives only one allele.</p> Signup and view all the answers

<p>A Test Cross involves crossing the individual with a homozygous recessive to observe the offspring, determining if the individual is homozygous dominant or heterozygous.</p> Signup and view all the answers

<p>Mendel found that both dominant and recessive traits reappeared in the F2 generation, disproving the blending inheritance theory.</p> Signup and view all the answers

<p>A dihybrid cross examines the inheritance of two different genes, each with two alleles, which helps understand the principle of independent assortment.</p> Signup and view all the answers

<p>An organism is homozygous recessive if it has two copies of the recessive allele, resulting in the expression of the recessive phenotype.</p> Signup and view all the answers

<p>The Punnett square predicts the possible genotypes of offspring based on the gametes of the parents by showing how alleles combine.</p> Signup and view all the answers

<p>Dominance refers to the phenomenon where the presence of a dominant allele masks the expression of a recessive allele in a heterozygous organism.</p> Signup and view all the answers

<p>Meiosis creates haploid gametes by separating homologous chromosomes, allowing for a mix of parental alleles in the offspring.</p> Signup and view all the answers

<p>The phenotypic ratio is 9:3:3:1.</p> Signup and view all the answers

<p>The F1 generation displays a light purple phenotype.</p> Signup and view all the answers

<p>Codominance occurs when both alleles are fully expressed; an example is human blood type AB.</p> Signup and view all the answers

<p>The gametes consist of WG, Wg, wG, and wg, totaling four types.</p> Signup and view all the answers

<p>Incomplete penetrance occurs when a dominant allele does not always manifest in the phenotype.</p> Signup and view all the answers

<p>The recombinant phenotypes are wrinkled yellow and wrinkled green.</p> Signup and view all the answers

<p>True breeding refers to organisms that consistently produce offspring with a specific phenotype, such as WWGG for smooth yellow seeds.</p> Signup and view all the answers

<p>Mendel established that dominant alleles completely mask recessive alleles, forming the foundation of classical genetics.</p> Signup and view all the answers