Bio Module 3- Genes, Genetics, and Cell Division

Activator

A protein that binds to the promoter to enhance the binding of RNA polymerase.

cAMP (Cyclic AMP)

A signaling molecule involved in glucose and energy metabolism in E. coli.

Coding region

The region of an operon that includes the genes for the biosynthesis enzymes.

Enhancers

DNA sequences that help augment transcription; sites for specific transcription factors.

Exons

Sequence present in final mature mRNA; protein-coding segments.

Gene

The basic unit of heredity; a sequence of DNA that codes for a functional product.

General transcription factors

Proteins that bind to the core promoter region to assist with binding RNA polymerase.

lac operon

A typical inducible operon that includes the genes needed to use lactose as an energy source.

Negative control

A mechanism where a repressor protein actively binds to the operator to keep the genes turned off.

Operator

A region of DNA to which a repressor protein can bind to block the action of RNA polymerase.

Operon

A block of genes needed for a specific function, encoded together and transcribed into a single mRNA.

Positive control

A mechanism where proteins bind to promoter sequences to turn genes on and activate them.

Primary transcript

The newly transcribed RNA molecule; also called pre-mRNA in eukaryotes.

Promoter

A DNA sequence upstream of the coding sequence to which RNA polymerase binds to initiate transcription.

Repression

A mechanism in which a repressor protein actively binds to the operator to keep the genes turned off.

Repressor

A protein that binds to an operator region to block the action of RNA polymerase.

RNA polymerase

The enzyme that synthesizes an RNA strand from a DNA template.

Specific transcription factors

Proteins that bind to various regions outside of the core promoter region and interact with the core promoter.

Transcriptional gene regulation

The primary method in prokaryotes to control what type of protein is expressed by regulating DNA transcription.

Transcription complex

The assembly of general transcription factors, RNA polymerase, and other proteins that initiate transcription.

Transcription factors

Proteins that control the initiation of transcription by binding to the promoter and regulatory elements.

trp operon

An operon containing the genes for the five tryptophan biosynthesis enzymes.

UTR (Untranslated Region)

Region just upstream (5' UTR) or downstream (3' UTR) of the protein-coding region in an RNA molecule.

Chromatin remodeling complex

A protein machine that slides nucleosomes down the DNA to open chromosomal regions.

Histones

Proteins that package and order DNA into structural units called nucleosome complexes.

Histone acetylation

The addition of acetyl groups to histone tails, which relaxes DNA binding and opens chromatin regions.

Nucleosomes

Structural units formed by the winding of DNA strands around histone proteins.

Alternate splicing

The mechanism of splicing differently to produce different proteins from the same gene.

Chemical modification of proteins

The addition or removal of groups to proteins to regulate their activity or lifespan.

Double stranded RNA (dsRNA)

RNA that is double-stranded and can cause gene silencing.

Export inhibition

A control mechanism preventing pre-mRNA from being transported from the nucleus to the cytoplasm.

Induction

The process where a small molecule inactivates a repressor or activates an activator to increase transcription.

Initiation complex

The complex that assembles to start the process of translation.

mRNA editing

A mechanism that changes the sequence of the primary transcript after transcription.

miRNA (microRNA)

Small regulatory RNA molecules that bind to complementary mRNA sequences to inhibit translation.

Post-transcriptional gene regulation

Regulation occurring after RNA is transcribed but before translation into protein.

Post-translational gene regulation

Regulation occurring after proteins are made, including chemical modifications and degradation.

Proteasome

An organelle that removes proteins marked for degradation and breaks them down.

RNA interference (RNAi)

A cellular process that protects the cell from infections by shutting off gene expression.

RNA splicing

The process of removing introns and reconnecting exons in the primary transcript.

siRNA (small interfering RNA)

Small regulatory RNA molecules that bind to mRNA to inhibit translation or target it for degradation.

Small RNAs

General term for small regulatory RNA molecules like miRNA and siRNA.

Spliceosomes

Complexes of proteins and RNA molecules that carry out RNA splicing.

Ubiquitin

A small protein that marks other proteins for degradation.

Ubiquitination

The process of adding a ubiquitin group to a protein, marking it for degradation.

Histones

Proteins associated with DNA that help form nucleosomes.

Nucleosome

A beadlike structure consisting of DNA wrapped around histones.

Chromatin

The complex of DNA and proteins that make up chromosomes.

Euchromatin

Loosely packed chromatin that is accessible for transcription.

Heterochromatin

Densely packed chromatin that is typically not accessible for transcription.

10 nm fiber

DNA wound around histones to form nucleosomes.

Solenoid

A 30-nm fiber formed by the condensation of the 10-nm fiber.

30 nm fiber

The solenoid structure formed by the condensation of the 10-nm fiber.

Centromere

The constricted region of a chromatid where sister chromatids are tightly attached.

Kinetochore

Protein structure on the centromere that attaches to the mitotic spindle.

Sister chromatids

Identical copies of a chromosome after DNA replication attached by cohesin proteins.

Cohesin proteins

Proteins that seal sister chromatids together until anaphase.

Karyotype

An arrangement of chromosomes according to length.

Haploid (n)

Cell or organism containing one set of chromosomes.

Diploid (2n)

Cell or organism containing two sets of chromosomes.

Homologous chromosomes

Chromosomes that are the same length and have the same genes in the same location.

Homolog

Individual chromosome from a homologous pair.

Daughter cell

One of the two identical cells produced after a parent cell has divided.

Interphase

A long preparatory period of the cell cycle during which chromosomes are replicated.

G1 phase

The first growth phase where the cell accumulates building blocks and energy reserves.

S or Synthesis phase

The phase during which nuclear DNA is duplicated.

G2 phase

The second growth phase where the cell replenishes energy and synthesizes proteins for chromosome movement.

M or Mitotic phase

The phase during which duplicated chromosomes and cytoplasm are separated.

Mitosis

The division of genetic material (nuclear division, or karyokinesis).

Centrosome

Structure containing a pair of centrioles that orchestrates chromosome movement during mitosis.

Prophase

The first stage of mitosis; chromatin coils and condenses into visible chromosomes.

Metaphase

Stage where sister chromatids line up along a linear plane in the middle of the cell.

Spindle equator (metaphase plate)

The plane through the center of the spindle where sister chromatids are positioned during metaphase.

Anaphase

The stage when sister chromatids separate and are pulled to opposite ends of the cell.

Telophase

The final stage of mitosis; two new daughter nuclei form at either end of the dividing cell.

Cytokinesis

The physical separation of the cytoplasmic components into the two daughter cells.

Cleavage furrow

A constriction formed by the contractile ring during cytokinesis in animal cells.

Contractile ring

The actin ring that separates daughter cells in animal cells during cytokinesis.

Cell Plate

Structure formed during plant cell cytokinesis that grows into a new cell wall.

Checkpoint

Points in the cell cycle where progression can be halted until conditions are favorable.

G1/S checkpoint

Determines whether all conditions are favorable for the cell to commit to division.

G2/M checkpoint

Ensures all chromosomes have been replicated and DNA is not damaged before entering mitosis.

Metaphase or Spindle checkpoint

Determines whether all sister chromatids are correctly attached to the spindle.

Growth factor

A signaling molecule that promotes cell division.

Proto-oncogene

A normal gene coding for positive cell cycle regulators.

Oncogene

A mutated proto-oncogene that can cause cancer.

Tumor suppressor gene

A gene that codes for negative regulator proteins that prevent uncontrolled division.

Binary fission

Prokaryotic cell division resulting in two identical daughter cells.

Septum

A wall formed across the cell during prokaryotic cell division.

Meiosis

A two-step cell division process resulting in four cells with half the number of chromosomes as the original cell.

Sexual reproduction

The union of two cells from two individual organisms.

Gametes

Haploid reproductive cells (sperm or egg).

Fertilization

The union of two haploid cells from two individual organisms.

Zygote

A diploid cell resulting from the fusion of two haploid gametes.

Meiosis I

The first round of meiotic cell division; sometimes termed reduction division.

Meiosis II

The second round of meiotic cell division following meiosis I.

Genetic variation

The diversity of alleles and genotypes in a population.

Prophase I

The first stage of meiosis I; homologous chromosomes condense and form complexes.

Synapsis

Formation of a close association between homologous chromosomes during prophase I.

Synaptonemal complex

A protein lattice that forms between homologous chromosomes during prophase I.