IB Biology Topic D2.2: Gene Expression Key Definitions

The percentage of twin pairs in which both twins share a trait or disease. A rate below 100% in monozygotic twins shows that the trait is not determined by genes alone.

DNA methylation involves the addition of a methyl group (–CH₃) to a cytosine base in DNA.

Enhancers are DNA sequences that increase the rate of transcription when activator proteins bind to them.

Epigenesis refers to the development of patterns of differentiation in cells, enabling them to perform specific functions.

Regulation of gene expression without altering the DNA sequence itself.

An epigenetic tag is a chemical modification to DNA or histone proteins that regulates gene expression without altering the underlying DNA sequence.

Gene expression is the process of using genetic information to produce functional products like proteins.

The genome is the complete set of genetic instructions that determines the structure, function, and traits of an organism.

Genomic imprinting is a form of epigenetic inheritance, where the expression of a gene depends on whether it is inherited from the mother or the father.

A protein that provides structural support for DNA in eukaryotic cells. Histones are positively charged, allowing them to interact with negatively charged DNA, helping to compact it into a condensed form called chromatin.

Hormones are chemical messengers that travel through the bloodstream to regulate various physiological processes.

Monozygotic twins (identical twins) arise when a single fertilized egg splits into two embryos.

mRNA degradation is the process by which mRNA molecules are broken down after they have served their purpose in protein synthesis.

The phenotype of an organism refers to its observable traits or characteristics, which result from the interaction between its genetic makeup (genotype) and the environment.

A promoter is a specific DNA sequence located near the start of a gene. It acts as a binding site for RNA polymerase and other proteins needed to initiate transcription.

The proteome is the complete set of proteins produced by a cell, tissue, or organism at a specific time.

A DNA sequence that decreases the rate of transcription when repressor proteins bind to it.

Transcription factors are proteins that control transcription by binding to specific DNA sequences.

The transcriptome is the complete set of RNA molecules transcribed from the genome in a cell at a specific time.