Glossary Molecular Biology and Computational Biology

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

Gap 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.

Gap 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.

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

Gel electrophoresis

Gene 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).


Gene amplification Repeated copying of a piece of DNA; a characteristic of tumor cells.


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.

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).

Gene family Group of closely related genes that make similar products.

Gene library

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.

Gene pool All the variations of genes in a species.


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

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.

Gene testing

Gene therapy An experimental procedure aimed at replacing, manipulating, or supplementing nonfunctional or misfunctioning genes with healthy genes.


Gene transfer Incorporation of new DNA into and organism's cells, usually by a vector such as a modified virus. Used in gene therapy.


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.

Genetic counseling Provides patients and their families with education and information about genetic-related conditions and helps them make informed decisions.

Genetic discrimination Prejudice against those who have or are likely to develop an inherited disorder.

Genetic engineering Altering the genetic material of cells or organisms to enable them to make new substances or perform new functions.

Genetic engineering technology

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

Genetic informatics

Genetic map

Genetic marker A gene or other identifiable portion of DNA whose inheritance can be followed.


Genetic material

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.

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

Genetic predisposition Susceptibility to a genetic disease. May or may not result in actual development of the disease.

Genetic screening Testing a group of people to identify individuals at high risk of having or passing on a specific genetic disorder.

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

Genetics The study of inheritance patterns of specific traits.

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

Genome project Research and technology-development effort aimed at mapping and sequencing the genome of human beings and certain model organisms.


Genomic library A collection of clones made from a set of randomly generated overlapping DNA fragments that represent the entire genome of an organism.


Genomic sequence

Genomics The study of genes and their function.

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

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).

Germ line The continuation of a set of genetic information from one generation to the next.


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.


Germ line genetic mutation

Global Alignment The alignment of two nucleic acid or protein sequences over their entire length. (

Greek-key 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.

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