| Term | Definition |
|---|---|
| adenine | A purine nitrogenous base found in both DNA and RNA that pairs with thymine in DNA or uracil in RNA. |
| base pairing | The specific pairing of nitrogenous bases between DNA strands (A-T and C-G) or in RNA (A-U). |
| circular chromosomes | Ring-shaped DNA structures typically found in prokaryotic organisms that contain genetic information. |
| cytosine | A pyrimidine nitrogenous base found in both DNA and RNA that pairs with guanine. |
| DNA molecules | Deoxyribonucleic acid molecules that store genetic information in living organisms. |
| eukaryotes | Organisms whose cells contain a membrane-bound nucleus and other membrane-bound organelles. |
| guanine | A purine nitrogenous base found in both DNA and RNA that pairs with cytosine. |
| hereditary information | Genetic material passed from parent organisms to offspring that determines inherited traits. |
| hereditary material | Genetic material that is passed from parent organisms to offspring and carries the instructions for life. |
| histones | Proteins around which DNA wraps to condense and organize chromosomes in eukaryotic cells. |
| linear chromosomes | Chromosomes with defined endpoints found in eukaryotic cell nuclei, as opposed to the circular chromosomes found in prokaryotes. |
| nucleic acid | Macromolecules composed of nucleotides containing carbon, hydrogen, oxygen, nitrogen, and phosphorus that store and transmit genetic information. |
| nucleotide | The monomer unit of nucleic acids, consisting of a five-carbon sugar, a phosphate group, and a nitrogenous base. |
| plasmids | Small, circular, extra-chromosomal DNA molecules found in prokaryotes and eukaryotes that carry genetic information. |
| prokaryotes | Single-celled organisms without a membrane-bound nucleus, such as bacteria and archaea. |
| purines | Nitrogenous bases with a double ring structure; includes adenine and guanine. |
| pyrimidines | Nitrogenous bases with a single ring structure; includes cytosine, thymine, and uracil. |
| RNA molecules | Ribonucleic acid molecules that can store and transmit genetic information in some organisms. |
| thymine | A pyrimidine nitrogenous base found in DNA that pairs with adenine. |
| uracil | A pyrimidine nitrogenous base found in RNA that pairs with adenine. |
| Term | Definition |
|---|---|
| 5' to 3' direction | The direction in which DNA is synthesized, from the 5' carbon of one sugar to the 3' carbon of the next sugar in the phosphate backbone. |
| complementary DNA | A newly synthesized strand of DNA that is formed based on the base-pairing rules with the template strand. |
| DNA polymerase | An enzyme that synthesizes new DNA strands by adding nucleotides in the 5' to 3' direction. |
| DNA replication | The process by which DNA makes an exact copy of itself, which can be subject to errors that cause mutations. |
| genetic information | The hereditary instructions encoded in DNA that direct the synthesis of proteins and determine organism traits. |
| helicase | An enzyme that unwinds the double helix structure of DNA by breaking hydrogen bonds between base pairs during replication. |
| lagging strand | The strand of DNA synthesized discontinuously in short fragments (Okazaki fragments) in the 5' to 3' direction during replication. |
| leading strand | The strand of DNA synthesized continuously in the 5' to 3' direction during replication. |
| ligase | An enzyme that joins DNA fragments together by forming phosphodiester bonds between adjacent nucleotides on the lagging strand. |
| replication fork | The Y-shaped structure formed during DNA replication where the double helix unwinds and new strands are synthesized. |
| RNA primer | A short RNA sequence synthesized by primase that provides the 3'-OH group required for DNA polymerase to begin DNA synthesis. |
| semiconservative replication | A mechanism of DNA replication in which each new DNA molecule consists of one original strand and one newly synthesized complementary strand. |
| template strand | The original strand of DNA that serves as a pattern for synthesizing a new complementary strand during replication. |
| topoisomerase | An enzyme that relieves tension and relaxes supercoiling in DNA ahead of the replication fork. |
| Term | Definition |
|---|---|
| 3' to 5' direction | The direction in which RNA polymerase reads the template DNA strand during transcription. |
| 5' to 3' direction | The direction in which DNA is synthesized, from the 5' carbon of one sugar to the 3' carbon of the next sugar in the phosphate backbone. |
| alternative splicing | The process by which different combinations of exons are joined together during mRNA processing, producing multiple versions of mature mRNA from a single gene. |
| anticodon | A three-base sequence on tRNA that base pairs with a complementary codon on mRNA during translation. |
| codon | A sequence of three nucleotides on mRNA that specifies a particular amino acid or stop signal during translation. |
| exon | A coding segment of a eukaryotic gene that is retained in the mature mRNA molecule after RNA processing. |
| genetic information | The hereditary instructions encoded in DNA that direct the synthesis of proteins and determine organism traits. |
| guanosine triphosphate cap | A modified guanosine nucleotide structure added to the 5' end of eukaryotic mRNA that aids in ribosomal recognition. |
| intron | A non-coding segment of a eukaryotic gene that is removed from the mRNA transcript during RNA processing. |
| poly-A tail | A string of adenine nucleotides added to the 3' end of eukaryotic mRNA that increases mRNA stability. |
| primary peptide sequence | The initial linear arrangement of amino acids in a protein as determined by the mRNA codon sequence during translation. |
| ribosome | The cellular structure composed of rRNA and proteins that catalyzes the synthesis of polypeptides during translation. |
| RNA polymerase | An enzyme that catalyzes the synthesis of RNA by reading a DNA template strand and linking RNA bases in sequence. |
| RNA processing | A series of enzyme-mediated modifications to eukaryotic mRNA transcripts, including capping, polyadenylation, and splicing. |
| template strand | The original strand of DNA that serves as a pattern for synthesizing a new complementary strand during replication. |
| transcription | The process by which RNA polymerase synthesizes RNA molecules using a DNA template strand. |
| transfer RNA | An RNA molecule that binds specific amino acids and uses anticodon sequences to recognize and pair with mRNA codons during translation. |
| translation | The process by which mRNA is decoded by ribosomes to synthesize a polypeptide chain. |
| Term | Definition |
|---|---|
| amino acid | Organic molecules that serve as the building blocks of proteins, each composed of a central carbon atom bonded to a hydrogen atom, a carboxyl group, an amine group, and a variable R group. |
| codon | A sequence of three nucleotides on mRNA that specifies a particular amino acid or stop signal during translation. |
| elongation | The stage of translation in which amino acids are sequentially added to the growing polypeptide chain. |
| eukaryotic | Referring to organisms that have a membrane-bound nucleus and organelles, such as animals, plants, and fungi. |
| genetic code | The set of rules by which nucleotide sequences in mRNA are translated into amino acid sequences in proteins. |
| genotype | The genetic makeup of an organism; the specific alleles present for each gene. |
| initiation | The first stage of translation in which the ribosome assembles on the mRNA at the start codon. |
| messenger RNA | The RNA molecule that carries genetic information from DNA and serves as the template for protein synthesis. |
| phenotype | The observable physical and biochemical characteristics of an organism, determined by both genetic and environmental factors. |
| polypeptide | A chain of amino acids linked together by peptide bonds. |
| prokaryotic | Referring to organisms that lack a membrane-bound nucleus and organelles, such as bacteria. |
| protein | Macromolecules composed of amino acids linked together, containing carbon, hydrogen, oxygen, nitrogen, and often sulfur, that perform diverse functions in cells. |
| retrovirus | A virus that uses reverse transcriptase to convert its RNA genome into DNA for integration into the host genome. |
| reverse transcriptase | An enzyme that synthesizes DNA from an RNA template, used by retroviruses to convert their RNA genome to DNA. |
| ribosomal RNA | The RNA component of the ribosome that catalyzes peptide bond formation. |
| ribosome | The cellular structure composed of rRNA and proteins that catalyzes the synthesis of polypeptides during translation. |
| rough endoplasmic reticulum | Endoplasmic reticulum with attached ribosomes on its cytoplasmic surface; site of synthesis for proteins destined for secretion or membrane insertion. |
| start codon | The codon AUG where translation begins, coding for the amino acid methionine. |
| stop codon | A codon that signals the termination of translation and the release of the completed polypeptide chain. |
| termination | The final stage of translation in which the ribosome releases the completed polypeptide chain. |
| transcription | The process by which RNA polymerase synthesizes RNA molecules using a DNA template strand. |
| transfer RNA | An RNA molecule that binds specific amino acids and uses anticodon sequences to recognize and pair with mRNA codons during translation. |
| translation | The process by which mRNA is decoded by ribosomes to synthesize a polypeptide chain. |
| Term | Definition |
|---|---|
| cell differentiation | The process by which cells become specialized through the selective expression of genes for tissue-specific proteins. |
| constitutively expressed | Genes that are continuously transcribed and translated at relatively constant levels. |
| coordinately regulated | The simultaneous regulation of multiple genes as a group, often in response to the same signal or regulatory mechanism. |
| epigenetic changes | Reversible modifications of DNA or histone proteins that affect gene expression without changing the DNA sequence. |
| gene products | The proteins or RNA molecules produced by the expression of genes that determine cellular function and organism phenotype. |
| inducible | Genes that are expressed only in response to specific environmental signals or regulatory molecules. |
| inducible system | A gene regulation system in prokaryotes where genes are turned on in response to the presence of a substrate or signal molecule. |
| operons | In prokaryotes, a cluster of genes under the control of a single regulatory sequence that are transcribed together as one unit. |
| phenotype | The observable physical and biochemical characteristics of an organism, determined by both genetic and environmental factors. |
| regulatory proteins | Proteins that bind to regulatory sequences to control whether genes are transcribed. |
| regulatory sequences | Stretches of DNA that interact with regulatory proteins to control the transcription of genes. |
| repressible system | A gene regulation system in prokaryotes where genes are turned off in response to the presence of a substrate or signal molecule. |
| tissue-specific proteins | Proteins whose expression is limited to particular cell types or tissues, contributing to cell differentiation. |
| transcription | The process by which RNA polymerase synthesizes RNA molecules using a DNA template strand. |
| transcription factors | Proteins that bind to specific DNA sequences (promoters or enhancers) to regulate the initiation of transcription and control gene expression. |
| Term | Definition |
|---|---|
| differential gene expression | The selective expression of different genes in different cells or at different times, resulting in variation in which proteins are produced. |
| enhancer | A DNA sequence that can be located upstream or downstream of a gene and where transcription factors bind to increase the rate of transcription. |
| gene expression | The process by which information from a gene is used to synthesize functional gene products, typically proteins, which can be influenced by environmental conditions. |
| gene regulation | The mechanisms that control when and how often a gene is expressed, determining the amount of gene product produced. |
| negative regulatory molecules | Molecules that inhibit gene expression by binding to DNA and blocking transcription. |
| phenotype | The observable physical and biochemical characteristics of an organism, determined by both genetic and environmental factors. |
| phenotypic differences | Observable variations in the physical or biochemical characteristics of cells or organisms resulting from differences in gene expression and protein production. |
| promoter | A DNA sequence located upstream of a gene where RNA polymerase and transcription factors bind to initiate transcription. |
| RNA polymerase | An enzyme that catalyzes the synthesis of RNA by reading a DNA template strand and linking RNA bases in sequence. |
| small RNA molecules | Short RNA sequences, such as microRNAs, that regulate gene expression by controlling mRNA translation or degradation. |
| transcription | The process by which RNA polymerase synthesizes RNA molecules using a DNA template strand. |
| transcription factors | Proteins that bind to specific DNA sequences (promoters or enhancers) to regulate the initiation of transcription and control gene expression. |
| transcription start site | The location on DNA where RNA polymerase begins synthesizing RNA, relative to which promoter and enhancer sequences are positioned. |
| Term | Definition |
|---|---|
| aneuploidy | An abnormal number of chromosomes resulting from nondisjunction, often causing new phenotypes. |
| beneficial mutation | A mutation that has a positive effect on the organism's phenotype or survival. |
| chromosome structure | The physical organization of chromosomes, including the arrangement and integrity of genetic material; alterations can lead to genetic disorders. |
| conjugation | A process of horizontal gene transfer in prokaryotes involving direct cell-to-cell transfer of DNA. |
| cystic fibrosis | A genetic disorder caused by mutations in the CFTR gene that disrupt ion transport in cells. |
| detrimental mutation | A mutation that has a negative effect on the organism's phenotype or survival. |
| DNA repair mechanisms | Cellular processes that identify and correct errors in DNA to maintain genetic integrity. |
| DNA replication | The process by which DNA makes an exact copy of itself, which can be subject to errors that cause mutations. |
| DNA sequences | The specific order of nucleotide bases (A, T, G, C) in a DNA molecule that encodes genetic information. |
| frameshift mutation | A type of mutation in which one or more nucleotides are inserted or deleted, causing the reading frame of the genetic code to shift. |
| genetic variation | Differences in DNA sequences and alleles that exist within a population. |
| genotype | The genetic makeup of an organism; the specific alleles present for each gene. |
| meiosis | A process of cell division in diploid organisms that produces haploid gamete cells, reducing chromosome number by half for sexual reproduction. |
| mitosis | A process of cell division in eukaryotes that produces two genetically identical daughter cells, each with a complete copy of the parent cell's genome. |
| mutation | An alteration in a DNA sequence that can cause changes in the type or amount of protein produced and the resulting phenotype. |
| mutations | Random changes in DNA sequences that create new genetic variations in populations. |
| natural selection | A major mechanism of evolution in which individuals with more favorable phenotypes are more likely to survive and reproduce, passing advantageous traits to subsequent generations. |
| neutral mutation | A mutation that has no effect on the organism's phenotype or protein function. |
| nondisjunction | The failure of chromosomes to separate properly during mitosis or meiosis, resulting in changes in chromosome number. |
| nonsense mutation | A type of point mutation that results in a premature stop codon, terminating protein synthesis early. |
| phenotype | The observable physical and biochemical characteristics of an organism, determined by both genetic and environmental factors. |
| point mutation | A type of mutation in which one nucleotide is substituted for a different nucleotide in the DNA sequence. |
| prokaryotes | Single-celled organisms without a membrane-bound nucleus, such as bacteria and archaea. |
| reading frame | The grouping of nucleotides into consecutive triplets (codons) that are read during translation to produce a protein. |
| recombination | The process by which genetic material is exchanged between homologous chromosomes, creating new combinations of alleles. |
| reproductive processes | Biological mechanisms that generate genetic variation and are conserved across different organisms. |
| sickle cell anemia | A genetic disorder caused by mutations in hemoglobin genes that result in abnormal red blood cell shape and reduced oxygen transport. |
| silent mutation | A type of mutation in which a change in the nucleotide sequence has no effect on the amino acid sequence or protein produced. |
| transduction | A process of horizontal gene transfer in prokaryotes where viruses transfer genetic information from one cell to another. |
| transformation | A process of horizontal gene transfer in prokaryotes where cells take up DNA from their environment. |
| transposition | The movement of DNA segments (transposons) within or between DNA molecules, creating genetic variation. |
| triploidy | A condition in which an organism has three complete sets of chromosomes instead of the normal two. |
| variation | Differences in traits among individuals within a population due to genetic and environmental factors. |
| Term | Definition |
|---|---|
| bacterial transformation | The process of introducing foreign DNA into bacterial cells, allowing them to take up and express new genetic material. |
| DNA denaturation | The process of separating double-stranded DNA into single strands, typically by heating. |
| DNA fingerprint | A unique pattern of DNA sequences from an individual that allows for comparison and identification of DNA samples. |
| DNA sequencing | Technology that determines the precise order of nucleotides in a DNA molecule. |
| gel electrophoresis | A laboratory process that separates DNA fragments based on their size and electrical charge by moving them through a gel matrix. |
| gene cloning | The process of creating identical copies of a specific DNA fragment for propagation and study. |
| genetic engineering techniques | Methods used to analyze, manipulate, or alter DNA and RNA in organisms. |
| polymerase chain reaction | A technique that amplifies specific DNA fragments through repeated cycles of denaturing, primer annealing, and DNA extension. |
| primer annealing | The binding of short DNA sequences (primers) to complementary regions on a template DNA strand during PCR. |
| transgenic animals | Animals that have been genetically modified to contain foreign DNA from another organism. |