gene expression

the activation or "turning on" of a gene that results in transcription and the production of mRNA

genome

the complete genetic material contained in an individual

structural gene

a gene that codes for a product, such as an enzyme, protein, or RNA, rather than serving as a regulator

operator

a short sequence of viral or bacterial DNA to which a repressor binds to prevent transcription (mRNA synthesis) of the adjacent gene in an operon

operon

a unit of gene regulation and transcription in bacterial DNA that consists of a promoter, an operator, and one or more structural genes

lac operon

a gene system whose operator gene and three structural genes control lactose metabolism in E. coli

repressor protein

a regulatory protein that binds to an operator and blocks transcription of the genes of an operon

regulator gene

a genetic unit that regulates or suppresses the activity of one or more structural genes

inducer

a substance that combines with and inactivates a repressor which allows the transcription of a gene

euchromatin

a region of DNA that is uncoiled and undergoing active transcription into RNA

intron

a segment of a structural gene that is transcribed but not translated

exon

in a sturctural gene, one of the segments that are ultimately transcribe and translated when the gene is expressed

pre-mRNA

precursor mRNA; the first strand of mRNA produced by gene transcription that contains both introns and exons

enhancer

a DNA sequence that recognizes certain transcription factors that can stimulate transcription of nearby genes

cell differentiation

the process by which a cell becomes specialized for a specific structure or function

homeotic gene

a gene that controls the development of a specific adult structure

homeobox

a DNA sequence within a homeotic gene that regulates development in animals

proto-oncogene

a gene that regulates normal cell division but that can become a cancer-causing oncogene as a result of mutation or recombination

oncogene

a gene that induces cancer, or uncontrolled cell proliferation

cancer

a tumor in which the cells begin dividing at an uncontrolled rate and become invasive

tumor

a growth that arises from normal tissue but that grows abnormally in rate and structure and lacks a function

tumor-suppressor gene

a gene that suppresses tumor formation but that, when mutated, causes a loss in cell function, which results in tumor formation

metastasis

the spread of cancer cells beyond the original site of growth

carcinogen

a cancer causing substance

carcinoma

a malignant tumor that grows in the skin or in the tissues that line organs

sarcoma

a malignant tumor that grows in bone or muscles tissue

lymphoma

a tumor in the lymphoid tissues

leukemia

a progressive, malignant disease of the blood-forming organs

transcription factor

a regulatory protein that bins to DNA and stimulates the transcription of certain genes