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Molecular Biology and Bioinformatics Glossary




Mature male or female reproductive cell (sperm or ovum) with a haploid set of chromosomes (23 for humans). (ORNL)


A space introduced into an alignment to compensate for insertions and deletions in one sequence relative to another. To prevent the accumulation of too many gaps in an alignment, introduction of a gap causes the deduction of a fixed amount (the gap score) from the alignment score. Extension of the gap to encompass additional nucleotides or amino acid is also penalized in the scoring of an alignment. (NCBI)


A position in an alignment that represents a deletion within one sequence relative to another. Gap penalties are requirements for alignment algorithms in order to reduce excessively-gapped regions. Gaps in alignments represent insertions that usually occur in protruding loops or beta-bulges within protein structures. (SMART)

GC-rich area

Many DNA sequences carry long stretches of repeated G and C which often indicate a gene-rich region. (ORNL)

Gel electrophoresis

See: electrophoresis (ORNL)


The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product (i.e., a protein or RNA molecule).
See also: gene expression (ORNL)

Gene amplification

Repeated copying of a piece of DNA; a characteristic of tumor cells.
See also: gene, oncogene (ORNL)

Gene chip technology

Development of cDNA microarrays from a large number of genes. Used to monitor and measure changes in gene expression for each gene represented on the chip. (ORNL)

Gene expression

The process by which a gene's coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into protein (e.g., transfer and ribosomal RNAs). (ORNL)

Gene family

Group of closely related genes that make similar products. (ORNL)

Gene library

See: genomic library (ORNL)

Gene mapping

Determination of the relative positions of genes on a DNA molecule (chromosome or plasmid) and of the distance, in linkage units or physical units, between them. (ORNL)

Gene pool

All the variations of genes in a species.
See also: allele, gene, polymorphism (ORNL)

Gene prediction

Predictions of possible genes made by a computer program based on how well a stretch of DNA sequence matches known gene sequences (ORNL)

Gene product

The biochemical material, either RNA or protein, resulting from expression of a gene. The amount of gene product is used to measure how active a gene is; abnormal amounts can be correlated with disease-causing alleles. (ORNL)

Gene testing

See: genetic testing, genetic screening (ORNL)

Gene therapy

An experimental procedure aimed at replacing, manipulating, or supplementing nonfunctional or misfunctioning genes with healthy genes.
See also: gene, inherit, somatic cell gene therapy, germ line gene therapy (ORNL)

Gene transfer

Incorporation of new DNA into and organism's cells, usually by a vector such as a modified virus. Used in gene therapy.
See also: mutation, gene therapy, vector (ORNL)

Genetic code

The sequence of nucleotides, coded in triplets (codons) along the mRNA, that determines the sequence of amino acids in protein synthesis. A gene's DNA sequence can be used to predict the mRNA sequence, and the genetic code can in turn be used to predict the amino acid sequence. (ORNL)

Genetic counseling

Provides patients and their families with education and information about genetic-related conditions and helps them make informed decisions. (ORNL)

Genetic discrimination

Prejudice against those who have or are likely to develop an inherited disorder. (ORNL)

Genetic engineering

Altering the genetic material of cells or organisms to enable them to make new substances or perform new functions. (ORNL)

Genetic engineering technology

See: recombinant DNA technology (ORNL)

Genetic illness

Sickness, physical disability, or other disorder resulting from the inheritance of one or more deleterious alleles. (ORNL)

Genetic informatics

See: bioinformatics (ORNL)

Genetic map

See: linkage map (ORNL)

Genetic marker

A gene or other identifiable portion of DNA whose inheritance can be followed.
See also: chromosome, DNA, gene, inherit (ORNL)

Genetic material

See: genome (ORNL)

Genetic mosaic

An organism in which different cells contain different genetic sequence. This can be the result of a mutation during development or fusion of embryos at an early developmental stage. (ORNL)

Genetic polymorphism

Difference in DNA sequence among individuals, groups, or populations (e.g., genes for blue eyes versus brown eyes). (ORNL)

Genetic predisposition

Susceptibility to a genetic disease. May or may not result in actual development of the disease. (ORNL)

Genetic screening

Testing a group of people to identify individuals at high risk of having or passing on a specific genetic disorder. (ORNL)

Genetic testing

Analyzing an individual's genetic material to determine predisposition to a particular health condition or to confirm a diagnosis of genetic disease. (ORNL)


The study of inheritance patterns of specific traits. (ORNL)


All the genetic material in the chromosomes of a particular organism; its size is generally given as its total number of base pairs. (ORNL)

Genome project

Research and technology-development effort aimed at mapping and sequencing the genome of human beings and certain model organisms.
See also: Human Genome Initiative (ORNL)

Genomic library

A collection of clones made from a set of randomly generated overlapping DNA fragments that represent the entire genome of an organism.
See also: library, arrayed library (ORNL)

Genomic sequence



The study of genes and their function. (ORNL)


The genetic constitution of an organism, as distinguished from its physical appearance (its phenotype). (ORNL)

Germ cell

Sperm and egg cells and their precursors. Germ cells are haploid and have only one set of chromosomes (23 in all), while all other cells have two copies (46 in all). (ORNL)

Germ line

The continuation of a set of genetic information from one generation to the next.
See also: inherit (ORNL)

Germ line gene therapy

An experimental process of inserting genes into germ cells or fertilized eggs to cause a genetic change that can be passed on to offspring. May be used to alleviate effects associated with a genetic disease.
See also: genomics, somatic cell gene therapy. (ORNL)

Germ line genetic mutation

See: mutation (ORNL)

Global Alignment

The alignment of two nucleic acid or protein sequences over their entire length. (NCBI)


a topology for a small number of beta sheet strands in which some interstrand connections going across the end of barrel or, in a sandwich fold, between beta sheets. (SCOP)

Guanine (G)

A nitrogenous base, one member of the base pair GC (guanine and cytosine) in DNA.
See also: base pair, nucleotide (ORNL)


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