Appendix C: 

 Glossary 



Gene families: Groups of closely related genes that make similar products. 



Gene library: See genomic lihrury. 



Gene mapping: Detemiination 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 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; abnomial amounts can be correlated with disease-causing alleles. 



Genetic code: The sequence of nucleotides, coded in triplets along the mRNA, that 

 determines the sequence of amino acids in protein synthesis. The DNA sequence of 

 a gene can be used to predict the mRNA sequence, and the genetic code can in turn 

 be used to predict the amino acid sequence. 



(ienetic engineering technologies: See reconihinant DNA technologies. 



Genetics: The study of the patterns of inheritance 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 projects: Research and technology development efforts aimed at mapping and 

 sequencing some or all of the genome of human beings and other organisms. 



Genomic library: A collection of clones made from a set of randomly generated 

 overlapping DNA fragments representing ti'e entire genome of an organism. 

 Compare lihrary. uridyecl library. 



Guanine (G): A nitrogenous base, one member of the base pair, G-C (guanine and 

 cytosine). 



Haploid: A single set of chromosomes (half the full set of genetic material), present 

 in the egg and spemT cells of animals and in the egg and pollen cells of plants. 

 Human beings have 23 chromosomes in their reproductive cells. Compare diploid. 



Heteroduplex: A double-stranded DNA molecule in which the two strands are not 

 completely complementary in base sequence and hence are not completely 

 base-paired, 



Homeo box: A short stretch of nucleotides whose sequence is virtually identical in all 

 the genes that contain it. It has been found in many organisms, from fruit flies to 

 human beings. In the fruitfly, a homeo box appears to determine when particular 

 groups of genes are expressed during development. 



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