Genetics Chapter 13: Evolutionary Synthesis

A phenomenon where a gene manipulates meiosis to favor the transmission of one allele over another.

The expected 50/50 chance of either allele being passed down.

A phenomenon where genes are close together on a chromosome, leading to inheritance patterns correlated with the proximity of the genes.

A single gene affecting multiple traits or phenotypes.

More than two alleles for a gene.

The way alleles interact to produce a phenotype; it doesn't predict the frequency of the allele.

A cross between an organism with an unknown genotype and an organism with a known genotype (usually homozygous recessive) to determine the unknown genotype.

Genes located close together on a chromosome that are likely to be inherited together.

Many genes are located on a single chromosome.

Traits aren't always inherited independently. Some traits are linked and inherit together more often than not due to their proximity on a chromosome.

Genetic material swapping during meiosis, creating new combinations of traits.

The distance between genes on a chromosome affects the chance of recombination.

One gene affects the expression of another gene.

Homologous chromosomes, which are two matching pairs of chromosomes, line up closely together on the cellular spindle during meiosis.

Different forms of a gene.

A single chromosome contains a large amount of genes, not just one.

The genetic makeup of an offspring

Different genotypes cannot occur together. (e.g., RR and rr cannot coexist)

The likelihood of an offspring having red flowers (given the possible genotypes)

The chance of an offspring inheriting an AABb genotype from AaBb and AaBB parents

The inheritance of alleles for one gene does not influence the inheritance of alleles for another gene.

A genetic situation in which neither allele is completely dominant over the other resulting in an intermediate phenotype

Both alleles contribute equally to the offspring and both traits are visible

An individual carrying two different heterozygous alleles (e.g., AaBb)

Changes in allele frequencies within a population across generations. Focuses on variation within a species and shorter timeframes.

Evolutionary changes above the species level. Focuses on the origin of new species and diversification over long periods.

Differences in genes and traits within a population.

The proportion of a specific allele in a population.

Mutations, gene flow, and genetic drift are the primary sources of genetic variation.

A change in the DNA sequence.

The movement of genes between populations.

Random changes in allele frequencies due to chance events.

Microevolution, the change in allele frequencies within a population, requires genetic variation. Meaning, there must be more than one allele for a particular gene present in the population.

Four main processes drive microevolution: mutation, gene flow, genetic drift, and natural selection. These processes, along with genetic variation, cause the shift in allele frequencies over time.

Macroevolution is the large-scale evolutionary change, often happening over longer periods, and resulting in significant changes like the emergence of new species or major evolutionary trends.

Macroevolution is essentially the cumulative effect of microevolution over extended periods. Small changes in allele frequencies within populations (microevolution) can eventually lead to larger-scale evolutionary transformations (macroevolution).

Quantitative genetics and population genetics use mathematical models to predict and study the effects of evolutionary processes like mutation, selection, drift, and gene flow on both Mendelian traits and quantitative traits.

Mating between related individuals, increasing homozygosity and decreasing heterozygosity.

Reduced fitness due to increased homozygosity resulting from inbreeding.

Having two identical alleles for a gene.

Having two different alleles for a gene.

A theoretical model where allele and genotype frequencies remain constant across generations.

The study and application of scientific principles to preserve biodiversity.

The state of physical, mental, and social well-being.

A process where individuals with traits that increase their survival and reproduction in a specific environment are more likely to pass on their genes.

The reproductive success of an individual, measured by the number of offspring it produces.

Natural selection requires variation in a trait, a non-random link between the trait and reproductive success, and the trait must be heritable.

A trait that enhances an organism's survival and reproduction in a specific environment.

Natural selection acts on the phenotypes of individuals, which are influenced by their underlying genotypes.

Natural selection leads to changes in allele frequencies across generations, shifting the distribution of traits in a population.

An example of how natural selection can lead to rapid evolutionary change. Insects that had a genetic variation allowing them to survive the pesticide became more frequent.

A population with a limited number of individuals. This means that the genetic makeup of the next generation is influenced by a random sample of alleles from the previous generation.

The difference between the true value of a population and the value observed in a finite sample. This causes allele frequencies to fluctuate in smaller populations.

The magnitude of change in allele frequencies due to genetic drift. Smaller populations experience stronger drift because random events have a bigger impact.

Genetic drift generally reduces genetic variation within a population. This is because alleles are lost by chance, leading to a decrease in heterozygosity.

Genetic drift can cause populations to diverge from each other over time, especially in the absence of gene flow. This is because random changes in allele frequencies accumulate in isolated populations.

In small populations, genetic drift can overwhelm natural selection. This means that harmful alleles can become more common, even though they reduce fitness.

Random mating in each generation helps to minimize the deviations from Hardy-Weinberg equilibrium (expected genotype frequencies) caused by genetic drift. However, drift still has an impact, especially in smaller populations.

Migration, or gene flow, is the movement of individuals between populations, which can alter allele frequencies. Higher migration rates lead to more gene flow and less divergence between populations.

A sudden decrease in population size due to random events like disease or habitat loss, which can significantly reduce genetic variation and increase the impact of genetic drift.

A special case of a bottleneck where a small group of individuals establishes a new population, often in a new geographic location, leading to reduced genetic variation in the new population.

A change in DNA sequence that is harmful or reduces an organism's fitness.

Bottlenecks can increase the frequency of deleterious mutations in isolated populations, as harmful alleles are more likely to become common by chance in a small population.

Bottlenecks can have negative consequences for human health. Examples include increased rates of genetic disorders in specific populations.

Genetic variation is crucial for a population's ability to adapt to changing environments. Bottlenecks and founder effects can limit this variation, making adaptation more challenging.

The reproductive success of an individual, measured by the number of offspring it produces.

Mutation, gene flow, genetic drift, and natural selection are the four main processes that drive changes in allele frequencies within a population.

Macroevolution is essentially the cumulative effect of microevolution over extended periods. Small changes in allele frequencies within populations (microevolution) can eventually lead to larger-scale evolutionary transformations (macroevolution).

Mating patterns where individuals choose partners based on factors other than random chance, such as relatedness or similarity in phenotype.

Individuals with similar phenotypes are more likely to mate than expected by chance.

An organism fertilizes its own eggs, leading to increased homozygosity and a reduced genetic diversity.

Migration, or gene flow, is the movement of individuals between populations. Higher migration rates lead to more gene flow and less divergence in allele frequencies between populations.

Inbreeding increases the frequency of homozygous genotypes and decreases the frequency of heterozygous genotypes. This deviation from Hardy-Weinberg equilibrium is temporary, and random mating can restore expected genotype frequencies within a few generations.

Inbreeding depression can exacerbate the loss of genetic variation in small populations, making it harder for them to adapt to environmental changes and increasing vulnerability to extinction.

Inbreeding can increase the frequency of recessive genetic disorders, leading to health problems in individuals and affecting population health overall.

Inbreeding can intensify the effects of genetic drift, as reduced genetic variation due to inbreeding makes populations more susceptible to random changes in allele frequencies.

Mutation, gene flow, genetic drift, and natural selection are the four main processes that drive changes in allele frequencies within a population.

Macroevolution is essentially the cumulative effect of microevolution over extended periods. Small changes in allele frequencies within populations (microevolution) can eventually lead to larger-scale evolutionary transformations (macroevolution).

Differences in genes and traits within a population. This is essential for populations to adapt to their environment.

Inbreeding causes a deviation from Hardy-Weinberg equilibrium. It increases the frequency of homozygous genotypes and decreases the frequency of heterozygous genotypes. However, this effect is temporary and can be reversed by a few generations of random mating.

Inbreeding can exacerbate the loss of genetic variation in small populations, making them less adaptable to environmental changes and more vulnerable to extinction.

Inbreeding increases the frequency of recessive genetic disorders, which can lead to health problems for individuals and impact overall population health.

Inbreeding can intensify the effects of genetic drift. Reduced genetic variation from inbreeding makes populations more susceptible to random changes in allele frequencies.

Inbreeding depression leads to reduced fitness in populations, making individuals less likely to survive and reproduce. This can have significant consequences for the long-term viability of populations.

Inbreeding depression highlights the importance of genetic diversity for the long-term health of populations. Understanding inbreeding depression is crucial for conservation efforts and can be applied to human health issues as well.

Explains inbreeding depression by stating that deleterious alleles (harmful alleles) are often recessive and become more prevalent in homozygous individuals due to inbreeding.

Gene flow can both promote and hinder local adaptation. It can spread beneficial alleles, but also introduce maladaptive ones from other populations.

A population adapting to its specific environment, leading to differences between populations in different environments.

Gene flow is essential for maintaining genetic diversity and preventing populations from becoming too isolated, reducing their ability to adapt to environmental changes.

High gene flow can homogenize populations, reducing genetic differences between them. This can hinder local adaptation but also promote the spread of beneficial alleles.

Natural selection requires variation in a trait, a non-random link between the trait and reproductive success, and the trait must be heritable.

Natural selection acts on the phenotypes of individuals, which are influenced by their underlying genotypes.

Natural selection leads to changes in allele frequencies across generations, shifting the distribution of traits in a population.