Mendelian Genetics and Evolutionary Biology Review

A comprehensive vocabulary flashcard set covering Mendelian inheritance, extensions to Mendel's principles, history of evolutionary thought, evidence for evolution, and natural selection.

Gene

A segment of DNA that codes for a specific trait and occupies a particular location (locus) on a chromosome.

Allele

One of the alternative versions of a gene that can occupy a given gene's locus.

Genotype

The specific combination of alleles an organism carries for a given gene.

Phenotype

An individual's observable physical or physiological traits, which result from its genotype and environmental influences.

Homozygous

Having two identical alleles for a given gene on homologous chromosomes.

Heterozygous

Having two different alleles for a given gene on homologous chromosomes.

Dominant Allele

An allele whose phenotypic effect is fully expressed in both homozygous and heterozygous genotypes, masking the recessive allele when present.

Recessive Allele

An allele whose phenotypic effect is expressed only in homozygous genotypes and is masked by a dominant allele in a heterozygote.

Particulate Inheritance Hypothesis

Gregor Mendel's hypothesis stating that heredity is transmitted by discrete, intact units (alleles) that separate intact during gamete formation rather than blending together.

Principle of Segregation

Mendel's principle stating that two alleles for a gene separate into different gametes during meiosis, specifically when homologous chromosomes separate during Meiosis I.

Monohybrid Cross

A cross between two individuals that focuses on the inheritance pattern of a single trait, yielding a $3:1$ phenotypic ratio in the F2 generation under complete dominance.

Principle of Independent Assortment

Mendel's principle stating that alleles of different genes transmit to gametes independently of one another, provided the genes are located on different chromosomes.

Dihybrid Cross

A mating between two individuals that are heterozygous for two distinct traits, producing a $9:3:3:1$ phenotypic ratio in the F2 generation under complete dominance.

Linkage

The phenomenon where two or more genes located close together on the same chromosome tend to be inherited together rather than assorting independently.

Sex-Linked Trait

A trait caused by a gene located on a sex chromosome (either X-linked or Y-linked).

Multiple Allelism

The existence of more than two common alleles for a single gene locus within a population, such as the coyote coat color K-locus ($K^B > k^{br} > k^y$).

Incomplete Dominance

A pattern of inheritance in which heterozygotes exhibit an intermediate phenotype between the phenotypes of the two homozygotes (e.g., pink flowers in four o'clocks).

Codominance

A pattern of inheritance in which heterozygotes simultaneously and fully express the distinct phenotypes associated with both alleles (e.g., roan coat color in Longhorn cattle or human ABO blood type $I^A I^B$).

Pleiotropy

A genetic pattern where a single gene influences multiple, seemingly unrelated phenotypic traits.

Epistasis (Gene Interaction)

A genetic interaction where the phenotypic expression of an allele at one locus depends on which alleles are present at another gene locus.

Polygenic Trait

A quantitative trait controlled by the combined additive or multiplicative effects of multiple genes, producing continuous variation in a population.

Phenotypic Plasticity

The ability of a single genotype to produce multiple distinct phenotypes depending on environmental conditions during development (e.g., temperature-dependent sex determination in alligators).

Evolution

The change in allele frequencies within a population over time.

Typological Thinking (Essentialism)

The philosophical view originating with Plato holding that species are static, unchanging entities defined by an idealized 'essence,' and that individual variation represents accidental imperfection.

Scale of Nature (Great Chain of Being)

Aristotle's hierarchical organization of living species into a fixed, unchanging linear scale from lower to higher complexity.

Uniformitarianism

The geological concept proposed by James Hutton and Sir Charles Lyell stating that past geological processes operated at the same rates and in the same manner as those observed in the present.

Inheritance of Acquired Characteristics

Jean-Baptiste de Lamarck's proposed mechanism of evolution stating that individual organisms change physically during their lifetime through use and disuse and pass those acquired traits to offspring.

Descent with Modification

Charles Darwin's proposal that modern species are modified descendants of ancestral species, connected across generations by common ancestry.

Transitional Feature

An intermediate physical trait in a fossil species that links an older ancestral group to a younger derived group (e.g., the forelimb bones of Tiktaalik).

Law of Succession

The pattern in the fossil record where extinct fossil species in a geographical region closely resemble living species found in the same area.

Vestigial Trait

A reduced or nonfunctional structure in an organism that is homologous to a fully functional structure present in ancestral or related species.

Genetic Homology

Similarity in DNA, RNA, or amino acid sequences among different species due to inheritance from a common ancestor.

Developmental Homology

Similarity in embryonic forms or developmental processes among different species due to common ancestry (e.g., pharyngeal pouches and tails in vertebrate embryos).

Structural Homology

Similarity in adult organismal structures (such as the arrangement of vertebrate forelimb bones) due to inheritance from a common ancestor.

Transformational Evolution

The outdated evolutionary model proposing that individual organisms alter their phenotypes in response to environmental demands and pass those modified traits directly to offspring.

Variational Evolution

The Darwinian evolutionary model proposing that differential survival and reproduction of pre-existing, variable individuals in a population changes the proportion of traits over generations.

Darwin's Four Postulates

The necessary conditions for natural selection: 1) Individuals in a population vary; 2) Some variations are heritable; 3) Survival and reproduction are variable; 4) Individuals that survive and reproduce best are a non-random sample of the population.

Biological Fitness

The relative ability of an individual to produce surviving, fertile offspring compared to other individuals in the same population.

Adaptation

A heritable trait that increases an individual's biological fitness in a specific environment compared to individuals lacking the trait.