Glossary of genetics
This is a glossary of terms and concepts commonly used in the study of genetics and related disciplines in biology. It is intended as introductory material for novices; for more specific and technical detail, please see the article corresponding to each term.
- One of the four nucleotide bases in DNA or RNA; pairs with thymine in DNA or uracil in RNA.
- affected relative pair
- An affected relative pair consists of two organisms related genetically that are both affected by the same trait. For example, two cousins who both have blue eyes are an affected relative pair since they are both affected by the allele coding for blue eyes.
- one of multiple alternative forms of a single gene, each of which is a viable DNA sequence occupying a given position, or locus on a chromosome. For example, in humans, one allele of the eye-color gene produces blue eyes and another allele of the eye-color gene produces brown eyes.
- Any chromosome that differs from an ordinary autosome in size, form, or behavior and which is responsible for determining the sex of an organism. In humans, the X chromosome and the Y chromosome are sex chromosomes.
- amino acid
- An organic compound containing amine and carboxyl functional groups, as well as a side chain specific to each individual amino acid. Out of nearly 500 known amino acids, a set of 20 are coded for by the standard genetic code and incorporated in sequence as the building blocks of polypeptides and hence proteins. The sequences of amino acids in polypeptide chains that form proteins determine the proteins' structure and function.
- Any chromosome that is not an allosome and is hence not involved in the determination of the sex of an organism. Unlike the sex chromosomes, the autosomes in a diploid cell exist in pairs, with the members of each pair having the same structure, morphology, and genetic loci.
- candidate gene
- centimorgan (cM)
- A unit for measuring genetic linkage defined as the distance between chromosomal loci for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01. Though it is not an actual measure of physical distance, it is used to infer the distance between two loci based on the apparent likelihood of a crossover occurring between them. Also called a map unit (m.u.).
- The part of a chromosome that links a pair of sister chromatids. During mitosis, spindle fibers attach to the centromere via the kinetochore.
- One copy of a newly copied chromosome which is still joined to the original chromosome by a centromere.
- chromosomal crossover
- chromosomal duplication
- A molecular "package" for carrying DNA in cells, organized as two double-helical DNA molecules that encode many genes. Some simple organisms have only one chromosome made of circular DNA, while most eukaryotes have multiple chromosomes made of linear DNA.
- classical genetics
- A series of three nucleotides in a coding region of a nucleid acid sequence which code for a particular amino acid or stop signal during protein synthesis. DNA and RNA molecules are each written in a language using four "letters" (four nucleotide bases), but the language used to construct proteins includes 20 "letters" (20 different amino acids). Codons provide the key that allows these two languages to be translated into each other. In general, each codon corresponds to a single amino acid (or stop signal), and the full set of codons is called the genetic code. The vast majority of living organisms use what is called the "standard" genetic code, which includes 64 possible permutations, or combinations, of three-letter nucleotide sequences that can be made from the four nucleotides. Of the 64 codons, 61 code for amino acids, and the remaining three code for stop signals. For example, the codon CAG represents the amino acid glutamine, and TAA is a stop codon. The genetic code is described as degenerate, or redundant, because a single amino acid may be coded for by more than one codon. When codons are read from the nucleotide sequence, they are read in succession and do not overlap with one another.
- copy number variation (CNV)
- One of the four nucleotide bases in DNA or RNA; pairs with guanine.
- An acronym for deoxyribonucleic acid, a polymeric molecule made of deoxyribonucleotides. Most often has the form of a "double helix", which consists of two paired DNA molecules and resembles a ladder that has been twisted. The "rungs" of the ladder are made of base pairs, or nucleotides with complementary hydrogen bonding patterns.
- DNA condensation
- DNA fingerprinting
- DNA polymerase
- DNA replication
- The process by which a DNA molecule copies itself, producing two identical copies of one original DNA molecule.
- DNA sequencing
- double helix
- endoplasmic reticulum (ER)
- The change in the heritable characteristics of biological populations over successive generations. In the most traditional sense, it occurs by changes in the frequencies of alleles in a population's gene pool.
- Any part of a gene that encodes a part of the final mature mRNA produced by that gene after introns have been removed by splicing. The term refers to both the sequence as it exists within a DNA molecule and to the corresponding sequence in RNA transcripts.
- extrachromosomal DNA
- fluorescence in situ hybridization (FISH)
- frameshift mutation
- A mutation caused by insertions or deletions of a number of nucleotides in a nucleic acid sequence that is not divisible by three. Because of the triplet nature by which nucleotides code for amino acids, a mutation of this sort causes a shift in the reading frame of the nucleotide sequence, resulting in a grouping of codons completely different from the original downstream of the mutation site. The earlier in the sequence the deletion or insertion occurs, the more altered the final gene product.
- A set of segments of a nucleic acid molecule that contains the information necessary to produce a functional RNA transcript in a controlled manner. In living organisms, it is a unit of heredity and typically encoded in DNA. A particular gene can have multiple different forms, or alleles, which are defined by different sequences of DNA.
- gene dosage
- gene drive
- gene duplication
- gene expression
- The process in which the information encoded in a gene is converted into a form useful for the cell. The first step is transcription, which produces a messenger RNA molecule complementary to the DNA molecule on which a gene is encoded. For protein-coding genes, the second step is translation, in which the messenger RNA is read by the ribosome to produce a protein.
- gene mapping
- gene pool
- The sum of all of the alleles shared by members of a single population.
- gene regulation
- gene silencing
- gene therapy
- gene trapping
- genetic code
- The set of rules by which information encoded within nucleic acids is translated into proteins by living cells. These rules define how sequences of nucleotide triplets called codons specify which amino acid will be added next during protein synthesis. The vast majority of living organisms use the same genetic code (sometimes referred to as the "standard" genetic code) but variant codes do exist.
- genetic counseling
- genetic disorder
- genetic drift
- genetic engineering
- genetic marker
- gene product
- genetic screening
- genetic testing
- The field of biology that studies genes and their inheritance.
- The entire complement of genetic material in the chromosome set of an organism, virus or organelle.
- The complement of alleles present in a particular individual's genome, which give rise to the individual's phenotype.
- germ line
- One of the four nucleotide bases in DNA or RNA; pairs with cytosine.
- The passing on of phenotypic traits from parents to their offspring, either through sexual or asexual reproduction. Offspring cells or organisms are said to inherit the genetic information of their parents.
- In a diploid organism, having two different alleles of a gene at a given genetic locus. Heterozygous genotypes are represented by a capital letter (indicating the dominant allele) and a lowercase letter (indicating the recessive allele), such as "Aa" or "Bb".
- homologous chromosomes
- A set of two matching chromosomes, one maternal and one paternal, that pair up with each other inside the nucleus during meiosis. They have the same genes at the same loci, but may have different alleles.
- homologous recombination
- horizontal gene transfer (HGT)
- Human Genome Project (HGP)
- map unit (m.u.)
- See centimorgan.
- medical genetics
- Mendelian inheritance
- messenger RNA (mRNA)
- microRNA (miRNA)
- missense mutation
- mitochondrial DNA (mtDNA)
- mobile genetic element
- Any change in the base pair sequence of DNA or RNA.
- nitrogenous base
- non-coding DNA
- non-coding RNA
- nonsense mutation
- Northern blotting
- nuclear membrane
- nucleic acid
- A long polymeric macromolecule made up of smaller monomers called nucleotides which are chemically linked to one another in a chain. Two specific nucleic acid molecules, DNA and RNA, are used in biological systems to encode the genetic blueprint of living organisms: the order, or sequence, of the nucleotides in DNA and RNA molecules encodes information that is translated into proteins which direct all of the chemical reactions necessary for life. DNA differs from RNA by its inclusion of thymine (T) as a nitrogenous base, whereas RNA includes uracil (U) instead. In DNA, the nucleotides are referred to in shorthand as A, C, T, and G; in RNA, the nucleotides are A, C, U, and G.
- An organic molecule that serves as the monomer, or subunit, of nucleic acids like DNA and RNA. The nucleotides relevant to biology include adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U).
- (pl. nuclei) A membrane-enclosed organelle found in eukaryotic cells. The nucleus contains most of a cell's genetic material, organized as chromosomes, and directs the activities of the cell by regulating gene expression.
- pedigree chart
- A short chain of amino acid monomers linked by peptide bonds.
- The observable physical or behavioral traits of an organism, largely determined by the organism's genotype.
- phosphate backbone
- point mutation
- A mutation where a single nucleotide base is changed, inserted, or deleted from a sequence of DNA or RNA.
- polygenic trait
- polymerase chain reaction (PCR)
- polymorphism (disambiguation)
- population genetics
- positional cloning
- A term used in medical genetics and genealogy to denote a particular subject being studied or reported on. Often prosposito for a male subject and prosposita for a female subject.
- A linear polymeric molecule made of amino acids linked by peptide bonds. Proteins carry out the majority of chemical reactions that occur inside cells.
- Punnett square
- reading frame
- A way of dividing the nucleotide sequence in a DNA or RNA molecule into a set of consecutive, non-overlapping triplets which is "read" by proteins during transcription and replication. In coding DNA, each triplet is referred to as a codon that is paired with a particular amino acid during translation. In general, only one reading frame (the open reading frame) in a given section of a nucleic acid is biologically relevant, but there are exceptions in a few organisms. A mutation that results in a shift in the normal reading frame affects all downstream codons and is called a frameshift mutation.
- recombinant DNA (rDNA)
- restriction enzyme
- restriction fragment length polymorphism (RFLP)
- reverse transcriptase
- ribosomal RNA (rRNA)
- RNA interference
- RNA polymerase
- Sanger sequencing
- shotgun sequencing
- silent mutation
- single nucleotide polymorphism (SNP)
- sister chromatids
- small interfering RNA (siRNA)
- solenoid fiber
- somatic cell
- somatic cell nuclear transfer (SCNT)
- Southern blotting
- spectral karyotype (SKY)
- start codon
- stem cell
- Any biological cell which has not yet differentiated into a specialized cell type and which can divide through mitosis to produce more stem cells.
- stop codon
- structure gene
- See point mutation.
- swivel point
- tandem repeat
- One of the four nucleotide bases in DNA molecules; pairs with adenine. In RNA, thymine is replaced with uracil.
- The first step in gene expression, in which a messenger RNA molecule complementary to particular gene encoded in DNA is synthesized by enzymes called RNA polymerases. To produce a functional protein, transcription is followed by translation.
- transcription factor
- transfer RNA (tRNA)
- The second step in gene expression, in which a messenger RNA molecule is read by the ribosome to produce a functional protein. Translation is always preceded by transcription.
- Western blotting
- wild type (WT)
- A term referring to the phenotype of the typical form of a species as it occurs in nature, a product of the standard "normal" allele at a given locus as opposed to that produced by a non-standard mutant allele. In genetics shorthand, wild-type alleles are often indicated by a "+" superscript.
Budd, A. (2012). "Introduction to genome biology: features, processes, and structures". Methods in Molecular Biology (855): 3–4.
- "Talking Glossary of Genetic Terms". genome.gov. 8 October 2017. Retrieved 8 October 2017.