IB Biology - D2.2 Gene Expression

Genetic Imprinting

process by which only one of the inherited genes for a trait is expressed; one copy is silenced by epigenetic tags

ex: tigons and ligers

Monozygotic Twins

identical twins resulting from the fertilization of one egg; same genome and very similar epigenomes

Reprogramming

when most (not all) of the epigenetic tags are removed at fertilization

Gene Expression

the mechanism by which genetic info in a gene is expressed as a protein

Phenotype

the observable traits of an organism, a result of its genotype and environmental factorsthat influence gene expression.

Genotype

the combination of alleles inherited by an organism

Promoter Region

regions located near the beginning of a gene; binding site for RNA polymerase

RNA Polymerase

enzyme that transcribes the gene into mRNA

Enhancers

regulatory sequences of DNA located away (sometimes very far) from the gene

Transcription Factors

regulatory proteins that bind to the enhancer region and activate the promoter region; can activate or repress transcription

Epigenesis

the process by which a multicellular organism develops from a zygote through a sequence of steps in which cells differentiate and organs form

Epigenetics

study of changes in organisms caused by modification of gene expression, via epigenetic tags, rather than changes in the genetic code; phenotype is changed but genotype is not

Epigenetic Tags

chemical markers that attach to DNA or histone proteins and influence gene transcription

Genome

all the genetic information of an organism; includes chloroplast and mitochondrial DNA

Transcriptome

all of the RNA molecules transcribed at a specific time within a cell or organism

Proteome

complete set of proteins present in a cell or organisms at a given time

Methyl Groups

CH₃; acts as epigenetic tags by attaching to the promoter region or histones

Epigenome

all of the epigenetic tags on the DNA and histone proteins; can be affected by environmental factors such as diet, cigarette smoke, and air pollution

Lac Operon

regulates the transcription of enzymes required for lactose metabolism; consists of promoter, operator, and three genes