BSC1005 Exam 3 Study Guide: Cell Division, Gene Inheritance, and Evolution

Vocabulary flashcards covering key terms and concepts for BSC1005 Exam 3 from Chapters 5, 23, and 27 of Inquiry into Life.

Cell Cycle

The orderly sequence of stages through which a cell passes from the time it is first formed until it divides into two new cells.

Interphase

The period of the cell cycle during which the cell carries out normal functions, increases in size, and duplicates its DNA across the G1, S, and G2 stages.

Mitosis

The division of the cell nucleus in which duplicated chromosomes are separated to produce two daughter nuclei with the identical chromosome number.

Cytokinesis

The division of the cytoplasm and its organelles into two separate daughter cells following nuclear division.

G1 Checkpoint

The primary checkpoint of the cell cycle that evaluates cell growth, nutrient availability, and DNA integrity before committing the cell to DNA synthesis.

G2 Checkpoint

The cell cycle control checkpoint that verifies whether DNA replication has completed accurately before the cell is permitted to enter mitosis.

M Checkpoint

The mitotic checkpoint that ensures all chromosomes are properly aligned and attached to the spindle fibers before sister chromatids separate.

Proto-oncogenes

Normal regulatory genes that encode proteins that promote the cell cycle and prevent apoptosis; mutations can convert them into cancer-causing genes.

Tumor Suppressor Genes

Genes that encode proteins that inhibit the cell cycle and promote apoptosis to prevent uncontrolled cell proliferation.

Oncogene

A cancer-causing gene formed by the mutation of a proto-oncogene that causes accelerated and unregulated cell division.

Diploid Number

The total number of chromosomes found in somatic cells, representing two sets of homologous chromosomes ($2n$).

Haploid Number

Half the diploid number of chromosomes ($n$), representing a single set of unpaired chromosomes characteristic of gametes.

Spindle

A microtubule-based apparatus that forms during cell division to organize, maneuver, and segregate chromosomes.

Prophase

The first phase of mitosis characterized by the condensation of chromatin into visible chromosomes, assembly of the spindle, and disintegration of the nucleolus.

Prometaphase

The phase of mitosis in which the nuclear envelope breaks down and spindle fibers connect to the kinetochores of duplicated chromosomes.

Metaphase

The mitotic phase during which chromosomes are aligned along the equatorial plane (metaphase plate) of the cell.

Anaphase

The mitotic phase where sister chromatids separate at their centromeres and are pulled toward opposite poles of the cell.

Telophase

The final stage of mitosis during which daughter chromosomes arrive at opposite poles, decondense back into chromatin, and new nuclear envelopes form.

Cleavage Furrow

An indentation that pinches the plasma membrane of an animal cell inward during cytokinesis, driven by a contractile ring of actin microfilaments.

Cell Plate

A membrane-bound structure that forms along the midline of a dividing plant cell via vesicle fusion, ultimately developing into a new cell wall.

Meiosis

A specialized form of nuclear division that reduces chromosome number from diploid ($2n$) to haploid ($n$), generating genetically diverse gametes.

Homologous Chromosomes

A pair of chromosomes that are identical in length, centromere position, and carry genes controlling the same inherited traits at corresponding loci.

Synapsis

The physical pairing of homologous chromosomes side by side along their lengths during prophase I of meiosis.

Gametes

Haploid sex cells, such as sperm or eggs, that unite during sexual reproduction.

Fertilization

The fusion of haploid male and female gametes to restore the diploid chromosome number in the resulting single-celled zygote.

Crossing-Over

The exchange of corresponding genetic segments between non-sister chromatids of homologous chromosomes during prophase I of meiosis.

Independent Assortment

The random and independent orientation and separation of maternal and paternal homologous chromosome pairs during metaphase I and anaphase I.

Interkinesis

A brief resting phase occurring between meiosis I and meiosis II during which no DNA replication takes place.

Zygote

The diploid cell produced by the union of a sperm and an egg at fertilization.

Allele

An alternative or variant form of a gene located at a specific position (locus) on a chromosome.

Mendel’s Law of Segregation

The genetic principle stating that each individual has two alleles for each trait, which separate during gamete formation so that each gamete receives only one allele.

True-Breeding Organism

An organism that is homozygous for a particular trait and invariably yields offspring identical to the parent when self-fertilized or mated with identical individuals.

Phenotype

The observable physical, physiological, or biochemical traits of an individual resulting from gene expression and environmental influences.

Genotype

The underlying genetic constitution of an organism, specified by the alleles present for particular traits.

Dominant Allele

An allele whose phenotypic effect masks the presence of a recessive allele in a heterozygous individual.

Recessive Allele

An allele whose phenotypic expression is concealed in heterozygotes and is only manifested in homozygous recessive individuals.

Homozygous

Possessing two identical alleles for a particular gene locus on homologous chromosomes.

Heterozygous

Possessing two different alleles for a particular gene locus on homologous chromosomes.

Monohybrid Cross

A genetic cross between two individuals that examines the inheritance patterns of a single pair of contrasting traits.

Punnett Square

A diagrammatic grid used in genetics to calculate and display all possible genotypic and phenotypic outcomes resulting from a genetic cross.

Testcross

A breeding experiment in which an individual exhibiting a dominant phenotype is crossed with a homozygous recessive individual to determine the dominant individual's genotype.

Mendel’s Law of Independent Assortment

The genetic principle stating that allele pairs for different traits separate independently of one another during gamete formation when genes are on nonhomologous chromosomes.

Dihybrid Cross

A genetic cross between individuals that are heterozygous for two distinct traits, typically producing a $9:3:3:1$ phenotypic ratio among offspring.

Evolution

Heritable changes in a population or species across generations, summarized by Darwin as descent with modification.

Inheritance of Acquired Characteristics

Lamarck's proposed mechanism of evolution asserting that physiological changes developed by an organism during its lifetime are transmitted to its offspring.

Natural Selection

The evolutionary mechanism wherein organisms possessing traits best suited to their environment exhibit higher survival and reproductive success, passing those traits to future generations.

Adaptation

An evolved anatomical, physiological, or behavioral feature that enhances an organism's survival and reproductive capability in its environment.

Artificial Selection

The intentional, human-directed breeding of organisms possessing desirable phenotypic traits over successive generations.

Microevolution

Small-scale genetic change involving shifts in allele frequencies within a population over a succession of generations.

Mutation

A permanent alteration in the nucleotide sequence of an organism's DNA, serving as the primary source of novel genetic variation.

Genetic Drift

Random fluctuations in allele frequencies within a population from generation to generation caused purely by chance events rather than natural selection.

Bottleneck Effect

A type of genetic drift that occurs when a population's size is drastically reduced by an environmental catastrophe or human impact, leaving an unrepresentative genetic pool.

Founder Effect

A type of genetic drift that occurs when a small, non-representative sample of individuals establishes a new population isolated from the parent population.

Gene Flow

The transfer of alleles into or out of a population resulting from the movement of fertile individuals or their gametes between populations.

Nonrandom Mating

Mating behavior wherein individuals select sexual partners based on specific phenotypes or genetic relatedness rather than pairing randomly.

Fitness

The reproductive success of an individual relative to other members of a population, determined by the number of viable, fertile offspring contributed to the next generation.

Macroevolution

Large-scale evolutionary patterns and changes occurring above the species level across extensive geological timescales, including speciation and extinction events.

Speciation

The evolutionary lineage-splitting event that results in the formation of one or more new and distinct reproductive biological species.

Allopatric Speciation

The divergence of populations into distinct species following physical geographic isolation that prevents gene flow between them.

Sympatric Speciation

The origin of new species from a common ancestral population occurring in the same geographic range without physical isolation.