BIO 101: Concept of Heredity and Evolution

Vocabulary flashcards covering Mendelian and non-Mendelian genetics, chromosome organization, inheritance patterns, molecular biology, mechanisms of evolution, and microbial heredity.

Heredity

The biological process through which traits and characteristics are transmitted from parents to their offspring through genetic material.

Genetics

The scientific study of heredity and variation, concerned with understanding how traits are inherited and how genetic differences arise; a term first coined by William Bateson in 1905.

Gregor Johann Mendel

An Austrian scientist and Augustinian monk ($1822–1884$) recognized as the Father of Genetics for his experiments on garden pea plants (Pisum sativum).

Alleles

Different forms of a gene that can occupy the same position (locus) on a chromosome.

Genotype

The complete genetic constitution of an organism, which determines its potential for traits.

Phenotype

The observable physical and physiological traits of an organism, resulting from the interaction between its genotype and the environment.

Homozygous

Possessing two identical alleles for a particular trait (e.g., $TT$ for tallness or $rr$ for dwarfness).

Heterozygous

Possessing two different alleles for a particular trait (e.g., $Tt$ for tallness).

Dominant Trait

A characteristic expressed in the phenotype even if only one copy of the allele is present.

Recessive Trait

A characteristic expressed in the phenotype only when both alleles are identical and recessive.

First Filial Generation ($F_1$)

The hybrid offspring produced from a cross between purebred parents with contrasting traits.

Second Filial Generation ($F_2$)

The generation of offspring produced by self-fertilization of $F_1$ hybrid plants, in which recessive traits reappear in an approximate phenotypic ratio of $3:1$.

Law of Dominance

Mendel's principle stating that dominant alleles are expressed in the phenotype even when only one copy is present, while recessive alleles require both copies to be expressed.

Law of Segregation

Mendel's principle stating that the two alleles for a gene separate during gamete formation so that each gamete receives only one allele.

Law of Independent Assortment

Mendel's principle stating that genes residing on different chromosomes segregate and sort independently of one another during gamete formation.

Transmission Genetics

A subfield of genetics (also known as Mendelian genetics) focusing on how traits and alleles are transmitted from parents to offspring.

Chromatin

The loosely packed form of DNA and associated proteins present in interphase that facilitates transcription and replication.

Nucleosomes

Eukaryotic structures consisting of DNA wrapped around histone proteins, forming higher-order chromatin structures.

Aneuploidy

A numerical chromosomal abnormality involving extra or missing chromosomes, such as Down syndrome (Trisomy $21$), Turner syndrome ($XO$), or Klinefelter syndrome ($XXY$).

Polyploidy

A chromosomal condition in which an individual possesses more than two complete sets of chromosomes.

Sex-linked Inheritance

An inheritance pattern for traits determined by genes located on a sex chromosome, such as red-green color blindness located on the $X$ chromosome.

Linkage

The tendency of genes located close together on the same chromosome to be inherited together, limiting independent assortment during meiosis.

Crossing Over

The process during meiosis where homologous chromosomes exchange DNA segments at chiasmata, resulting in allele recombination.

Punnett Square

A diagrammatic tool used to predict all possible allele combinations and phenotypic ratios in offspring based on parental genotypes.

Incomplete Dominance

A non-Mendelian inheritance pattern where a heterozygous genotype results in an intermediate phenotype between the two homozygous conditions.

Codominance

A non-Mendelian inheritance pattern where both alleles in a heterozygote are fully and simultaneously expressed in the phenotype.

Extranuclear Inheritance

The transmission of traits controlled by DNA located outside the nucleus, such as in mitochondria or chloroplasts, which is typically inherited maternally.

Mutation

A heritable change in the DNA sequence that serves as the primary source of genetic variation.

Lamarckism

An early evolutionary theory proposed by Jean-Baptiste Lamarck emphasizing the inheritance of acquired characteristics and the development or extinction of organs based on use and disuse.

Natural Selection

The evolutionary process proposed by Charles Darwin and Alfred Russel Wallace in which organisms with advantageous heritable traits survive and reproduce more successfully.

Gene Flow

The movement of individuals or genetic material between distinct populations, increasing genetic diversity.

Genetic Drift

Random fluctuations in allele frequencies within a population due to chance events, particularly influential in small populations.

Speciation

The evolutionary process by which new species arise through geographical (allopatric) or ecological/behavioral (sympatric) reproductive isolation.

Vertical Gene Transfer

The direct transmission of genetic material from parent to offspring during reproduction, such as via binary fission in bacteria.

Horizontal Gene Transfer (HGT)

The exchange of genetic material between distantly related or unrelated organisms bypassing traditional reproduction, occurring via transformation, transduction, or conjugation.

Transformation

A mechanism of horizontal gene transfer in which a bacterial cell takes up free fragments of extracellular DNA from its environment.

Transduction

A mechanism of horizontal gene transfer in which bacterial DNA is transferred from one host cell to another by a bacteriophage.

Conjugation

A mechanism of horizontal gene transfer involving direct cell-to-cell contact to transfer DNA, often via plasmids.