Genetics, Cell Cycle, and Biotechnology Lecture Notes

Comprehensive vocabulary flashcards covering the cell cycle, mitosis, meiosis, cancer biology, gene regulation, Mendelian genetics, chromosomal mutations, and biotechnology.

Cell Cycle

The "life cycle" of a cell, spanning the stages from its formation to its division into daughter cells.

Interphase

The period in a cell's life where it grows, duplicates DNA, and prepares for cell division; includes the $G_1$, $S$, and $G_2$ phases.

G0 Phase

An active, non-dividing state entered by cells that do not proceed past the $G_1$ checkpoint.

Anchorage Dependence

An environmental requirement where cells must be in contact with another solid surface in order to divide.

Density-dependent Inhibition

A regulatory phenomenon where crowded cells stop dividing after forming a single layer because cell density is optimal.

Growth Factors

Proteins in mammalian cells required for cell division; an example is vascular endothelial growth factor (VEGF), which stimulates the growth of new blood vessels during fetal development and after injury.

Cell Cycle Control System

A cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle through hard stop checkpoints.

G1 Checkpoint

A cell cycle checkpoint that verifies whether the cell has enough resources to fully replicate its DNA before advancing to the $S$ phase.

G2 Checkpoint

A cell cycle checkpoint assessing whether the cell has synthesized enough cytoplasm and phospholipids to form two daughter cells.

M Checkpoint

The metaphase checkpoint that verifies whether all chromosomes are properly aligned at the metaphase plate and attached to spindle fibers.

Proto-oncogene

A normal gene that codes for proteins responsible for promoting healthy cell growth, division, and survival; conceptually likened to the "gas pedal" of a car.

Tumor Suppressor Gene

A gene that codes for proteins responsible for slowing cell division, repairing damaged DNA, or triggering cell death; conceptually likened to the "brakes" of a car.

Oncogene

A mutated, altered, or overactive form of a proto-oncogene that causes uncontrolled cell growth.

Apoptosis

Programmed cell death triggered by severely damaged DNA or loss-of-function mutations to eliminate abnormal cells.

Benign Tumor

A noncancerous mass of abnormal cells that develops in one part of the body, remains encapsulated, and does not spread to other tissues.

Malignant Tumor

A mass of abnormally reproducing cells capable of invading neighboring tissues and spreading to other parts of the body.

Metastasis

The spread of cancer cells beyond their original primary site to distant parts of the body.

Carcinoma

A category of cancer that originates in epithelial cells, including the skin and the linings of internal tissues and organs.

Sarcoma

A category of cancer that originates in connective tissues, such as bone and muscle.

HeLa Cells

A continuously dividing, "immortal" line of human cancer cells maintained in culture since 1951, derived from donor Henrietta Lacks.

Gene Expression

The entire set of cellular processes by which the information stored in a gene is used to synthesize functional gene products (RNA or proteins).

Operon

A cluster of genes in prokaryotes with related functions that are regulated together under the control of a single promoter and operator.

Operator

A regulatory DNA sequence within an operon where an activator or repressor protein binds to control transcription.

Promoter

A specific sequence of DNA recognized by RNA polymerase as the binding site to initiate transcription.

Activator

A transcription factor protein that promotes gene expression by facilitating the binding of RNA polymerase to the promoter.

Repressor

A protein that binds to regulatory DNA sequences (such as operators or silencers) to inhibit transcription.

lac Operon

An inducible operon in Escherichia coli containing genes for lactose metabolism, which is repressed in the absence of lactose and turned on when allolactose binds and inactivates the repressor.

Nucleosome

The basic bead-like unit of DNA packaging in eukaryotes, consisting of a segment of DNA wrapped around an octamer core of $8$ histone proteins.

Histone Acetylation

The addition of acetyl groups to positively charged histone tails, loosening their attachment to negatively charged DNA to permit transcription.

Exon

A coding region of a eukaryotic gene that is retained and expressed in mature mRNA after RNA processing.

Intron

A non-translated intervening sequence of nucleotides in eukaryotic pre-mRNA that is spliced out before translation.

Spliceosome

A large complex of proteins and RNA molecules that cuts out introns and splices exons together during eukaryotic mRNA processing.

Alternative Splicing

A process during gene expression that generates distinct mRNA isoforms and different protein products from a single pre-mRNA transcript by selecting different combinations of exons.

Competitive Inhibitor

A regulatory molecule that mimics the substrate and competes directly for binding to an enzyme's active site.

Noncompetitive Inhibitor

An enzyme inhibitor that binds to an allosteric site rather than the active site, altering the enzyme's three-dimensional conformation and rendering it nonfunctional.

Kinase

An enzyme that transfers a phosphate group from ATP to a target protein, inducing a conformational change that alters protein activity.

Cellular Differentiation

The developmental process by which an unspecialized cell acquires distinct structural and functional characteristics to become a specialized cell type.

Totipotent

Describing a stem cell that has the potential to divide and differentiate into every specialized cell type required to form an entire organism.

Nuclear Transplantation

A cloning method in which the nucleus of an unfertilized egg or zygote is removed and replaced with the nucleus of an adult somatic cell.

Recombinant Plasmid

A bacterial plasmid vector that has been opened by a restriction endonuclease and resealed with a foreign DNA fragment of interest using DNA ligase.

CRISPR-Cas9

A gene-editing tool derived from bacterial immune systems that uses guide RNA and the Cas9 endonuclease to introduce precise double-stranded breaks in target DNA.

Gene Knockout

A genetic technique using tools like CRISPR-Cas9 to permanently disrupt, disable, or eliminate the expression of a specific gene.

Polymerase Chain Reaction (PCR)

A thermocyclic laboratory technique used to rapidly amplify millions of copies of a specific DNA segment through rounds of denaturation, primer annealing, and elongation.

Gel Electrophoresis

A technique that separates macromolecules (such as DNA fragments) based on size and electrical charge as they migrate through a gel matrix toward the positive pole.

Short Tandem Repeats (STRs)

Short repetitive sequences of $2\text{–}6$ base pairs occurring in tandem along chromosomal DNA, differing widely in repeat count between individuals.

CODIS

The Combined DNA Index System, an automated FBI database of DNA profiles utilizing standardized STR loci ($13$ core loci originally, expanded to $20$ in 2017) to match crime scene evidence.

Central Dogma

The framework describing the unidirectional flow of genetic information inside a biological system: $\text{DNA} \rightarrow \text{mRNA} \rightarrow \text{Protein}$.

Purines

A class of double-ring nitrogenous bases found in nucleotides, consisting of adenine ($A$) and guanine ($G$).

Pyrimidines

A class of single-ring nitrogenous bases found in nucleotides, consisting of thymine ($T$), cytosine ($C$), and uracil ($U$).

Transfer RNA (tRNA)

An adaptor RNA molecule with a cloverleaf structure of three loops that carries a specific amino acid at one end and displays a complementary anticodon at the other.

Codon

A three-nucleotide sequence in mRNA that specifies a particular amino acid or serves as a start ($AUG$) or stop signal during translation.

Anticodon

A specialized three-base sequence located on a tRNA loop that pairs complementarily with an mRNA codon during translation.

Replisome

The multi-protein complex of enzymes and structural proteins (including helicase, primase, and DNA polymerase) that coordinates replication at a replication fork.

Helicase

An enzyme that unzips double-stranded DNA by breaking the hydrogen bonds between base pairs ahead of the replication fork.

Topoisomerase

An enzyme that binds ahead of the replication fork to relieve structural strain and supercoiling caused by DNA unwinding.

Phosphodiester Bond

A covalent linkage that connects the $3'$ hydroxyl group of one deoxyribose sugar to the $5'$ phosphate group of an adjacent nucleotide.

Leading Strand

The newly synthesized DNA strand elongated continuously toward the advancing replication fork in the $5' \rightarrow 3'$ direction.

Lagging Strand

The newly synthesized DNA strand made discontinuously away from the replication fork as a series of short Okazaki fragments in the $5' \rightarrow 3'$ direction.

DNA Ligase

An enzyme that catalyzes the formation of phosphodiester bonds to join adjacent Okazaki fragments and seal nicks in the sugar-phosphate backbone.

Thymine Dimer

A covalent lesion formed between adjacent thymine bases in DNA resulting from ultraviolet radiation exposure, distorting the double helix.

Exonuclease

An enzymatic activity (such as the $3' \rightarrow 5'$ proofreading ability of DNA polymerase) that excises mismatched nucleotides from the free end of a polynucleotide strand.

Codominance

An inheritance pattern where the phenotypic effects of both alleles at a locus are fully and distinctly expressed in heterozygous individuals, such as roan coloration ($RW$) in cattle.

Polygenic Inheritance

The additive inheritance pattern where a single phenotypic character is controlled by multiple independent genes, producing continuous variation with a normal distribution.

Linked Genes

Genes located close together on the same chromosome that tend to be inherited together as a unit during meiosis.

Pedigree

A diagrammatic family tree recording ancestral relationships and the incidence of specific phenotypic traits across multiple generations.

Genotype

The genetic composition or specific combination of alleles possessed by an organism at one or more gene loci.

Phenotype

The observable physical, physiological, or biochemical traits of an organism, determined by its genotype and environment.

Principle of Segregation

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

Principle of Independent Assortment

Mendel's second law stating that allele pairs for different genes assort into gametes independently of one another during metaphase I of meiosis.

Point Mutation

A chemical mutation involving a change in a single nucleotide base pair within a DNA sequence, including substitutions, insertions, or deletions.

Missense Mutation

A base substitution mutation that changes a codon so that it encodes a different amino acid, altering the resulting protein's structure or function.

Nonsense Mutation

A base substitution that prematurely converts an amino-acid-specifying codon into a stop codon, producing an abnormally shortened, nonfunctional protein.

Chromosomal Deletion and Duplication

Structural chromosome mutations where a chromosomal fragment breaks off and is permanently lost (deletion) or where a segment is copied and repeated (duplication).

Chromosomal Inversion and Translocation

Structural chromosome alterations where a segment breaks, reverses orientation, and reattaches (inversion), or where a segment reattaches to a different, non-homologous chromosome (translocation).

Germline Mutation

A mutation occurring in reproductive gametes or germ cells, making the genetic alteration heritable across generations.

Somatic Mutation

A non-heritable genetic mutation arising in non-germline body cells that can propagate within the tissue via mitosis but cannot be passed to offspring.

Nondisjunction

The failure of homologous chromosomes to separate in meiosis I, or sister chromatids to separate in meiosis II, resulting in aneuploid gametes.

Karyotype

A visual display of an individual's complete condensed chromosome set arranged in homologous pairs by length and centromere location.

Trisomy 21

A human chromosomal condition (Down syndrome) characterized by having three copies of chromosome $21$, resulting from nondisjunction.

Klinefelter Syndrome

A human genetic condition in biological males caused by an extra X chromosome ($XXY$), often resulting in sterile individuals with underdeveloped testes.

Turner Syndrome

A chromosomal condition in biological females lacking a second sex chromosome ($X0$), characterized by sterility and immature sex organs.

Homologous Chromosomes

A pair of chromosomes possessing the same length, centromere position, and loci containing genes for the same characteristics, one inherited from each parent.

Locus

The specific physical location of a particular gene along the length of a chromosome.

Ploidy

The number of complete sets of chromosomes present in the nucleus of a cell, such as haploid ($n$), diploid ($2n$), or polyploid.

Meiosis

A two-stage reductive division process in sexually reproducing organisms that reduces chromosome number from diploid ($2n$) to haploid ($n$), creating $4$ genetically distinct daughter cells.

Tetrad

A four-part structure formed during prophase I of meiosis by the synapsis of a replicated homologous chromosome pair.

Crossing Over

The reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I, generating recombinant chromosomes.

Chiasma

The microscopic X-shaped region representing the physical point of contact where crossing over occurred between non-sister chromatids.

Binary Fission

A form of asexual reproduction in prokaryotes in which the circular chromosome replicates and the single cell splits into two genetically identical daughter cells.

Sister Chromatids

Two identical copies of a duplicated chromosome joined along their length and attached at a common centromere.

Centromere

The specialized DNA region where sister chromatids are most closely attached to each other and where kinetochores form for spindle attachment.

Kinetochore

A specialized protein complex assembled on the centromere that links sister chromatids to mitotic spindle microtubules during division.

Cleavage Furrow

A shallow contractile groove that pinches the plasma membrane inward during cytokinesis to divide animal cells.

Cell Plate

A double membrane and cell wall precursor formed across the midline of a dividing plant cell during cytokinesis.