Pharmacogenetics Glossary
adenine (A) - a base in DNA and RNA that always bonds with thymine (T) in DNA,
and with uracil (U) in RNA.
alleles - two different forms or versions of a gene that occupy corresponding positions
on homologous chromosomes. A person has two alleles of a trait--one from each
parent.
amino acids - the basic building blocks of proteins; there are twenty different types
linked together in different sequences to form different proteins.
bases - the molecular building blocks of DNA and RNA: adenine (A), cytosine (C),
guanine (G), thymine (T), and in RNA only, uracil (U). In DNA, A attaches only to T,
and C attaches only to G. In RNA, A attaches only to U, and C attaches only to G.
base pairs - the pairs of complementary bases that form the rungs of DNA: adenine
(A) pairs with thymine (T), cytosine (C) pairs with guanine (G).
base sequence - the order of bases in DNA.
cell - the basic unit of life; the smallest basic part of every living thing that can
function by itself. It is made of a nucleus surrounded by cytoplasm, organelles
(similar to organs in a body) and proteins. Each cell contains the entire genome.
chromosome - a long coiled strand in the nucleus, made up of DNA and protein.
There are 46 human chromosomes, each containing DNA for hundreds or thousands
of individual genes.
codon - a special code to make amino acid; a sequence of three nucleotides.
cytoplasm - all the organelles and materials inside a cell between the cell membrane
and the nucleus.
cytosine (C) - a base in DNA that always bonds with guanine (G).
deletion - the loss of a segment of genetic material.
deoxyribonucleic acid - see DNA
diploid - a cell or organism that has two complete sets of chromosomes, as opposed to
haploid, or those with only one member of each pair of the same chromosomes.
DNA (deoxyribonucleic acid) - a large double-stranded, spiraling molecule that
contains genetic instructions for growth, development and replication. It is organized
into bodies called chromosomes and found in the cell nucleus.
double helix - a common name for DNA, referring to the double-stranded, spiraling
structure of the molecule.
enzymes - the biological catalysts that speed up a chemical reaction.
exon - a gene segments that has instructions for making a protein, as opposed to
introns, which don’t have these instructions.
gene - the unit of heredity in chromosomes; a segment of double-stranded DNA.
gene expression - the way information in a gene is changed to a protein or RNA. The
DNA sequence is changed into RNA and usually (not always) then changed into
protein.
gene transcription - the first step in gene expression where the gene’s DNA sequence
is copied into messenger RNA.
gene translation - the method where transcribed messenger RNA directs the making
of proteins from amino acids.
genetic code - all the genes a living thing has inherited. They determine appearance,
function, growth, behavior, etc.
genetic disease - a disease caused by a genetic mutation.
genetic marker - a landmark that identifies a certain spot on a chromosome.
genetics - the study of genes and heredity, or how characteristics are passed from
parents to children.
genetic testing or screening - a technique used to find out whether a person or
organism has a particular gene.
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genome - all the genetic information necessary to build a living organism. It is
species-specific.
genotype - all the traits, dominant and recessive, that an organism inherits. This is
different from the phenotype, or acquired observable traits.
guanine (G) - a base in DNA and RNA that always bonds with cytosine (C).
haploid - cells that have a single set of chromosomes, or half the full set of genetic
material, as opposed to diploids. Sperm and egg cells are haploid.
heterozygous - refers to having dissimilar alleles of one or more genes, as opposed to
homozygous.
homozygous - refers to having an identical pair of alleles, one from each parent, as
opposed to heterozygous.
introns - DNA sequences without instructions for making protein that come between
those sequences with instructions for making protein (exons). Introns are not in
messenger RNA, and it is not known what they are for.
mutation - a permanent change in a DNA sequence that can be passed on. It can be a
change in genetic information, addition of information, or deletion of information.
nucleotide - the building block of DNA (rungs on the “ladder” of the DNA double
helix) made up of four molecules that occur in pairs--adenine (A) with thymine (T),
and cytosine (C) with guanine (G). Thousands of nucleotides are linked to form a
DNA or RNA molecule.
nucleus - the center part of the cell. It contains 6 feet of DNA in 23 pairs of
chromosomes and is the largest part of the cell. Living things are divided into
eukaryotes (whose cells have nuclei) and prokaryotes (whose cells have no nuclei).
phenotype - all the observable traits a person inherits, as opposed to the genome, or
all the traits inherited.
polymorphisms - the differences in DNA sequences that occur naturally. They are
used as genetic markers because researchers can use them to tell apart DNA from
different sources.
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promoter - a segment of DNA that acts as controlling element in expression of a
gene. Marks the place of the beginning of gene transcription.
protein - a molecule made up of amino acids linked together. They are the body’s
workhorses whose function can be as enzymes, structural components, or signaling
molecules.
RNA (ribonucleic acid) - single-stranded nucleic acid (similar to double-stranded
DNA) containing the bases adenine (A), cytosine (C), guanine (G), and uracil (U).
The different forms include messenger RNA (mRNA), transfer RNA (tRNA), and
ribosomal RNA (rRNA), which are all part of making protein.
thymine (T) - a base in DNA that always bonds with adenine (A).
transcription - the process by which DNA passes genetic information to RNA. The
first step in producing proteins.
translation - process by which RNA makes proteins.
uracil (U) - a base in RNA that bonds only with adenine (A).
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