Gene Expression and Regulation Overview

DNA

A molecule that carries genetic information.

RNA

A nucleic acid that plays a role in coding, decoding, regulation, and expression of genes.

DNA replication

The process by which a DNA molecule makes a copy of itself.

transformation

The genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material.

bacteriophage/phage

A type of virus that infects bacteria.

double helix

The structure formed by double-stranded molecules of nucleic acids, such as DNA.

antiparallel

Referring to the opposite orientation of the two strands of DNA.

base pairing

The specific hydrogen bonding between nucleotides in DNA and RNA.

origins of replication

Specific sequences in the genome where replication begins.

semiconservative replication

The method of DNA replication in which each new DNA molecule consists of one old strand and one new strand.

replication fork

The area where the DNA double helix is unwound to allow replication.

helicases

Enzymes that unwind the DNA double helix during replication.

topoisomerase

An enzyme that alleviates the tension in the DNA helix ahead of the replication fork.

single-strand binding proteins

Proteins that bind to single-stranded DNA and prevent it from re-annealing.

RNA primer

A short strand of RNA that serves as a starting point for DNA synthesis.

primase

An enzyme that synthesizes RNA primers during DNA replication.

DNA polymerase III

An enzyme responsible for synthesizing new DNA strands.

DNA polymerase I

An enzyme that replaces RNA primers with DNA nucleotides.

leading strand

The DNA strand that is synthesized continuously during replication.

lagging strand

The DNA strand that is synthesized in short fragments during replication.

Okazaki fragments

Short sequences of DNA nucleotides synthesized on the lagging strand.

DNA ligase

An enzyme that joins Okazaki fragments together.

mismatch repair

The process by which the cell identifies and corrects mismatched nucleotides.

nuclease

An enzyme that cuts DNA or RNA, removing nucleotides.

telomere

The repetitive nucleotide sequences at the ends of chromosomes.

nucleotide excision repair

A DNA repair mechanism that removes damaged DNA segments.

telomerase

An enzyme that extends the telomeres of chromosomes.

chromatin

The complex of DNA and proteins that forms chromosomes.

histones

Proteins that help package and order DNA into structural units called nucleosomes.

nucleosome

The basic unit of DNA packaging, consisting of a segment of DNA wound around a core of histone proteins.

heterochromatin

Tightly packed form of DNA, which is transcriptionally inactive.

gene expression

The process by which information from a gene is used to synthesize a functional gene product, typically proteins.

transcription

The process of copying a segment of DNA into RNA.

messenger RNA (mRNA)

The type of RNA that carries the genetic information from DNA to the ribosome.

translation

The process by which ribosomes synthesize proteins using mRNA as a template.

ribosomes

Molecular machines that facilitate the translation of mRNA into proteins.

triplet code

The genetic code that consists of three nucleotide bases that correspond to a specific amino acid.

codon

A sequence of three nucleotides in mRNA that specifies an amino acid.

template strand

The strand of DNA that is used as a template for RNA synthesis.

reading frame

The way nucleotides in mRNA are divided into codons.

RNA polymerase

The enzyme that synthesizes RNA from a DNA template.

promoter/terminator

Sequences in DNA that signal the start and end of transcription.

transcription factors

Proteins that regulate the transcription of genes.

TATA box

A DNA sequence that indicates where a genetic sequence can be read and decoded.

RNA processing

The modifications that occur to RNA before it is translated into protein.

5' cap/poly-A tail

Modifications added to the ends of mRNA to protect it and facilitate translation.

RNA splicing

The process of removing introns and joining exons in mRNA.

introns/exons

Introns are non-coding sequences, while exons are coding sequences in RNA.

spliceosome

A complex that removes introns from pre-mRNA.

ribozymes

RNA molecules that have catalytic properties.

alternative RNA splicing

A process that allows a single gene to code for multiple proteins.

transfer RNA (tRNA)

The type of RNA that carries amino acids to the ribosome during translation.

anticodon

A sequence of three bases in tRNA that is complementary to a codon in mRNA.

ribosomal RNAs (rRNAs)

The type of RNA that makes up the ribosome.

P site/ A site/ E site

The three sites in a ribosome where tRNA molecules bind during translation.

signal peptide

A short peptide sequence that directs the transport of a protein.

mutation

A change in the DNA sequence that can lead to changes in protein function.

point mutation

A mutation that affects a single nucleotide.

substitution mutation

A type of point mutation where one base is replaced by another.

silent mutation

A mutation that does not change the amino acid sequence of a protein.

missense mutation

A mutation that results in a different amino acid being incorporated into a protein.

nonsense mutation

A mutation that creates a premature stop codon in the protein sequence.

insertion

A mutation involving the addition of one or more nucleotide bases.

deletion

A mutation involving the removal of one or more nucleotide bases.

frameshift mutation

A mutation that shifts the reading frame of the genetic message.

mutagens

Agents that cause mutations in DNA.

operon

A cluster of genes under the control of a single promoter.

operator

A segment of DNA that a repressor protein can bind to, inhibiting transcription.

repressor

A protein that inhibits gene expression by binding to the operator.

regulatory gene

A gene that codes for a protein that regulates gene expression.

repressible operon

An operon that is usually on but can be turned off.

inducible operon

An operon that is usually off but can be turned on.

lac operon

An example of an inducible operon that is involved in lactose metabolism.

trp operon

An example of a repressible operon that is involved in tryptophan synthesis.

cyclic AMP (cAMP)

A signaling molecule that plays a role in the regulation of gene expression.

differential gene expression

The process by which cells with the same DNA express different genes.

histone acetylation

The addition of acetyl groups to histones, which can enhance gene expression.

DNA methylation

The addition of methyl groups to DNA, which can suppress gene expression.

epigenetics

The study of changes in gene expression that do not involve changes to the underlying DNA sequence.

control elements

DNA sequences that regulate the transcription of nearby genes.

enhancers

DNA sequences that increase the likelihood of transcription of a particular gene.

proteasomes

Protein complexes that degrade unneeded or damaged proteins.

RNAi

A biological process in which RNA molecules inhibit gene expression.

siRNAs

Small interfering RNAs that play a role in RNA interference.

miRNAs

MicroRNAs that regulate gene expression by targeting mRNA.

differentiation

The process by which cells become specialized in structure and function.

morphogenesis

The biological process that causes an organism to develop its shape.

induction

The process by which one group of cells influences the development of another group.

determination

The process by which a cell becomes committed to a specific fate.

pattern formation

The development of spatial organization in an organism.

homeotic genes (Hox)

Genes that regulate the development of anatomical structures.

lethal genes

Genes that can cause the death of an organism.

maternal effect gene/bicoid

A gene that affects the development of the embryo based on the mother's genotype.

oncogenes

Genes that have the potential to cause cancer.

proto-oncogenes

Normal genes that can become oncogenes due to mutations.

tumor suppressor genes

Genes that help prevent uncontrolled cell growth.