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Amino acid A building block of proteins.
There are 20 amino acids, each of which is
coded for by three adjacent nucleotides in a
Anticipation The disease process in which
symptoms show up earlier and are increasingly
severe in each generation.
Biofilm A slime layer that develops naturally
when bacteria congregate on surfaces.
The field of biology specializing
in developing hardware and software to store
and analyze the huge amounts of data being
generated by life scientists.
The industrial use of living
organisms or biological methods derived through
basic research; examples range from genetic engineering
to making cheese or bread.
Chromatin The organization and dense packaging
of DNA in the nucleus of cells.
Chromosome A cellular structure containing
genes. Chromosomes are composed of DNA and
proteins. Humans have 23 pairs of chromosomes
in each body cell, one of each pair from the
mother and the other from the father.
Circadian Pertaining to a period of about
24 hours; applied especially to rhythmic biological
repetition like the sleep-wake cycle.
Clone In genetics, the process of making many
copies of a gene or a whole organism. The term
also refers to the isolation and manipulation of
of human genetics by comparisons with the
genetics of other organisms.
Diploid Having two copies of each
DNA Abbreviation for deoxyribonucleic acid,
the molecule that contains the genetic code for all
life forms except for a few viruses. It consists of
two long, twisted chains made up of nucleotides.
Each nucleotide contains one base, one phosphate
molecule and the sugar molecule deoxyribose.
The bases in DNA nucleotides are adenine,
thymine, guanine and cytosine.
DNA chip See microarray.
An enzyme that copies DNA.
Enzyme A substance (often a protein) that
speeds up, or catalyzes, a chemical reaction without
being permanently altered or consumed.
Epigenetics The study of heritable changes in
gene function that occur without a change in the
Eukaryote An organism whose cells have
a membrane-bound nucleus.
Exon A DNA sequence in a gene that codes
for a gene product.
Gene A segment of a DNA molecule that
contains information for making a protein or,
sometimes, an RNA molecule.
Gene chip See microarray.
The process by which
genes are first converted to messenger RNA and
then to proteins.
Genetics The scientific study of genes and
heredity—of how particular qualities or traits
are transmitted from parents to offspring.
Genome All of an organism's genetic material.
Genomics A "scaled-up" version of genetic
research in which scientists can look at large
numbers or all of the genes in an organism at
the same time.
Haploid Having one copy of each chromosome,
as in a sperm or egg.
Haplotype A set of closely linked genes or
DNA polymorphisms inherited as a unit.
Histone A type of protein found in chromosomes;
histones attached to DNA resemble
"beads on a string."
Homeobox A DNA sequence found in genes
involved in the regulation of the development
of animals, fungi and plants.
Imprinting The phenomenon in which a gene
may be expressed differently in an offspring
depending on whether it was inherited from
the father or the mother.
Intron A DNA sequence, or the RNA sequence
transcribed from it, that interrupts the sequences
coding for a gene product (exon).
Meiosis The type of cell division that creates
egg and sperm cells.
Microarray Sometimes called a gene chip or
a DNA chip. Microarrays consist of large numbers
of molecules (often, but not always, DNA)
distributed in rows in a very small space.
Microarrays permit scientists to study gene
expression by providing a snapshot of all the
genes that are active in a cell at a particular time.
MicroRNA A short piece of single-stranded
RNA that does not encode a protein and controls
the expression of genes.
The cell's power plant,
supplying the energy to carry out all of the cell's
jobs. Each cell contains up to 1,000 mitochondria.
The structures contain their own small
genomes, called mitochondrial DNA.
Mutation A change in a DNA sequence.
Nucleotide A building block of DNA or
RNA. It includes one base, one phosphate molecule
and one sugar molecule (deoxyribose in
DNA, ribose in RNA).
Nucleus The structure in the eukaryotic cell
containing most of its genetic material.
The study of how people's
genetic make-up affects their responses
Protein A molecule consisting of subunits
called amino acids. Proteins are the cell's main
building materials and do most of a cell's work.
Hybrid DNA produced
in the laboratory by joining pieces of DNA from
Replication The process by which DNA
copies itself in order to make a new genome to
pass on to a daughter cell.
Ribosome The cell structure in which proteins
are manufactured. Most cells contain
thousands of ribosomes.
RNA Abbreviation for ribonucleic acid, the
molecule that carries out DNA's instructions for
making proteins. It consists of one long chain
made up of nucleotides. Each nucleotide contains
one base, one phosphate molecule and the sugar
molecule ribose. The bases in RNA nucleotides
are adenine, uracil, guanine and cytosine.
RNA interference (RNAi)
process in which double-stranded RNAs trigger
the destruction of specific RNAs.
An enzyme that transcribes
a DNA sequence, creating mRNA.
RNA splicing The process by which introns
are removed and exons are joined together
from an RNA transcript to produce an mRNA
Sequencing Sometimes called DNA sequencing
or gene sequencing. Discovering the exact
order of the building blocks (see nucleotides) of
a particular piece of DNA.
Stem Cell A cell that can develop into many
different cell types in the body.
A field that seeks to study
the relationships and interactions between various
parts of a biological system (metabolic
pathways, organelles, cells and organisms) and
to integrate this information to understand how
biological systems function.
Telomere A repeated DNA sequence that caps
the ends of chromosomes.
The first major step in gene
expression, in which the information coded in
DNA is copied into a molecule of RNA.
Translation The second major step in gene
expression, in which the instructions encoded in
RNA are carried out by making a protein or starting
or stopping protein synthesis.
Variant A different version of a gene, one that
has a slightly different sequence of nucleotides.