D2.2 Gene expression (HL) Notes

Phenotype

The observable traits or characteristics of an organism, resulting from the interaction of its genotype and environment.

Genotype

The genetic makeup of an organism, including all its genes.

Transcription

The process of converting a specific gene's DNA sequence into messenger RNA (mRNA).

RNA polymerase

The enzyme responsible for synthesizing RNA from a DNA template during transcription.

Promoter

A specific DNA sequence where RNA polymerase binds to initiate transcription.

Elongation

The stage of transcription where RNA polymerase unwinds DNA and synthesizes the RNA strand.

Termination

The completion of transcription when RNA polymerase reaches a termination sequence and releases the mRNA.

mRNA processing

The modifications that mRNA undergoes after transcription, including the addition of a 5' cap and a poly-A tail, and splicing out introns.

Translation

The process in which the mRNA sequence is decoded to produce a polypeptide chain at ribosomes.

Codon

A sequence of three nucleotides in mRNA that codes for a specific amino acid.

tRNA

Transfer RNA; a molecule that carries amino acids to the ribosome during translation.

Polypeptide

A chain of amino acids that fold into a functional protein.

Protein function

The roles that proteins perform in organisms, such as enzymatic, structural, or transport functions.

Cell differentiation

The process by which cells become specialized in function, leading to varying cell types.

Epigenesis

The development of patterns of differentiation in multicellular organisms, guided by epigenetic modifications.

Epigenetic modifications

Chemical changes to DNA or histone proteins that regulate gene activity without altering the DNA sequence.

DNA methylation

The addition of a methyl group to DNA, often silencing gene expression.

Histone modification

Chemical alterations to histone proteins that affect how tightly DNA is packed and gene accessibility.

Genetic determinism

The concept that genes alone determine an organism's traits, without considering environmental influences.

Feedback regulation

The process by which the end product of a pathway influences its own production through controlling gene expression.

Silencer

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

Enhancer

A DNA sequence that increases transcription when activator proteins bind to it.

Transcription factor

Proteins that control the transcription of specific genes by binding to nearby DNA.

Genomic imprinting

A form of epigenetic inheritance where the expression of a gene depends on its parental origin.

Monozygotic twins

Identical twins that develop from a single fertilized egg, sharing the same genetic material.

Lac operon

A model of gene regulation in prokaryotes that controls the metabolism of lactose.

Inducer

A substance that initiates gene expression by binding to a repressor protein.

Repressor protein

A protein that binds to an operator and blocks transcription of genes.

Structural genes

Genes that code for proteins that play roles in metabolism or structure.

RNA stability

The lifespan of an mRNA molecule, affecting how long it is available for translation.

Nucleus

The membrane-bound organelle in eukaryotic cells where transcription occurs.

Cytoplasm

The fluid portion of the cell where translation occurs on ribosomes.

Chronic stress

A prolonged state of stress that can alter epigenetic tags, affecting gene expression.

Adaptive responses

Changes in gene expression that allow an organism to adjust to environmental changes.

Methyl group

A functional group derived from methane; involved in DNA methylation.

Amino acids

The building blocks of proteins, linked together in a polypeptide chain.

Reversible changes

Epigenetic modifications that can be undone, unlike mutations in the DNA sequence.

Poly-A tail

A sequence of adenine nucleotides added to the 3' end of mRNA to protect it from degradation.

Splicing

The process of removing non-coding regions (introns) from pre-mRNA.

Functional proteins

Proteins that have a specific role or activity within a biological system.

Nucleotide sequence

The order of nucleotides in a DNA or RNA strand that determines genetic information.

The TATA box

A conserved sequence within promoters that aids in the binding of RNA polymerase.

Chromatin

The complex of DNA and proteins that forms chromosomes within the nucleus.

Signal transduction

The process by which a cell responds to external signals through changes in gene expression.

Cell signals

Molecules that communicate information to trigger cellular responses.

Homeostasis

The maintenance of stable internal conditions in an organism despite external changes.

Transcription initiation complex

The assembly of transcription factors and RNA polymerase at the promoter to begin transcription.

Nuclease

An enzyme that cleaves the chains of nucleotides in nucleic acids.

Molecular chaperones

Proteins that assist in the proper folding of other proteins.

Cellular metabolism

The set of chemical reactions that occur in cells to maintain life.

Programmed cell death

A regulated process that leads to the elimination of cells, maintaining tissue homeostasis.

Phenotypic plasticity

The ability of an organism to change its phenotype in response to environmental conditions.

Transgenerational epigenetic inheritance

The transmission of epigenetic tags from one generation to the next.

Mitosis

The process of cell division that results in two genetically identical daughter cells.

Meiosis

The process of cell division that results in gametes with half the number of chromosomes.