Bio 2100: Molecular Biology, Mitosis, Meiosis, and Genetics

Comprehensive vocabulary flashcards covering the Central Dogma, chromosome structure, mitosis, meiosis, Mendelian inheritance, and complex inheritance extensions.

Central Dogma of Molecular Biology

The framework describing the directional flow of genetic information within cells from DNA to RNA via transcription, and from mRNA to proteins via translation.

Reverse Transcriptase

An enzyme that serves as an exception to the standard Central Dogma by catalyzing the synthesis of DNA from an RNA template.

Crystallin

A transparent protein encoded by the crystallin gene in DNA that packs tightly into the lens cells of the eye to focus light.

Replicated Chromosome Structure

A duplicated chromosome composed of two identical sister chromatids joined at a centromere, capped by telomeres at the terminal ends, and formed by DNA double helices wrapped around histone proteins.

Sister Chromatids

Two identical copies of a replicated chromosome formed during interphase that share identical genetic sequences and alleles, originating from one parent.

Homologous Chromosomes

A pair of matched chromosomes carrying the same genes at the same loci—one inherited maternally and one paternally—which may carry different alleles.

Centromere

The specialized region of a replicated chromosome where sister chromatids are joined and where kinetochores attach to spindle microtubules during cell division.

Polyploidy

A chromosomal condition in which an organism or cell possesses more than the normal two complete sets of chromosomes, such as triploid ($3N$) or tetraploid ($4N$).

Aneuploidy

A chromosomal condition characterized by an abnormal number of individual chromosomes within a set (such as trisomy), distinct from polyploidy which involves entire additional sets.

Karyotype

The complete visual profile of an individual's metaphase chromosomes, arranged and numbered in homologous pairs by size, centromere position, and banding patterns.

Cell Cycle

The regular sequence of cellular growth and division consisting of Interphase ($G_1$, $S$ phase for DNA synthesis, and $G_2$) followed by the Mitotic (M) phase.

Mitosis

A form of eukaryotic nuclear division that segregates replicated sister chromatids to produce two genetically identical daughter cells maintaining the original ploidy ($2n \rightarrow 2n$).

Meiosis I

The first division of meiosis wherein homologous chromosome pairs synapse and segregate into separate cells, reducing the ploidy from diploid ($2n$) to haploid ($n$).

Meiosis II

The second meiotic division in which sister chromatids separate into distinct haploid cells, resulting in four genetically distinct gametes.

Crossing Over

The physical breakage and reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis.

Gametes

Haploid ($n$) reproductive cells (such as sperm and egg) produced by meiosis in germ cells that unite during fertilization to form a diploid ($2n$) zygote.

Principle of Segregation

Mendel's first law stating that two alleles of a single gene separate from each other during gamete formation in meiosis so that each gamete carries only one allele.

Principle of Independent Assortment

Mendel's second law stating that alleles of different genes assort independently of one another into gametes during meiosis when located on different chromosomes.

Dihybrid Cross

A genetic cross between parental organisms that are both heterozygous for two distinct traits, producing an $F_2$ phenotypic ratio of $9:3:3:1$ when genes assort independently.

Rule of Multiplication

A mathematical rule stating that the joint probability of two independent events occurring simultaneously is calculated by multiplying their individual probabilities.

Rule of Addition

A mathematical rule stating that the probability of any one of two or more mutually exclusive outcomes occurring is calculated by summing their individual probabilities.

True-Breeding

A homozygous genotype that always produces offspring with the same phenotype when self-fertilized or mated with an individual of identical genotype.

Multiple Allelism

The presence of three or more distinct alleles of a single gene within a population, as observed with the $I^A$, $I^B$, and $i$ alleles of the human ABO blood group system.

Codominance

An inheritance pattern in which the phenotypes produced by both alleles in a heterozygote are fully and equally expressed, such as the $I^A I^B$ genotype expressing both A and B antigens.

Incomplete Dominance

An inheritance pattern where neither allele is completely dominant, resulting in a heterozygous phenotype that is an intermediate blend between the homozygous parental phenotypes.

Incomplete Penetrance

A genetic scenario in which individuals carrying a specific dominant or disease-associated genotype fail to express the associated phenotype, as seen in polydactyly.

Environmental Effects (Gene Expression)

The modification of an organism's phenotypic expression by external factors such as temperature, illustrated by Himalayan rabbits developing dark fur at cooler body extremities.

Epistasis

A gene interaction in which the allele of one gene masks or overrides the phenotypic expression of alleles of another gene, such as the dominant inhibitor allele ($I$) preventing pigment allele ($C$) expression in White Leghorns.

Sex-Linked Genes

Genes physically located on sex chromosomes (primarily the X chromosome), causing phenotypic inheritance ratios that differ between male and female offspring.

Reciprocal Cross

A paired experimental cross where the sexes associated with respective parental phenotypes are reversed, utilized to determine if a trait is autosomal or sex-linked.