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Amino acids
A group of small molecules that join to form proteins,
amino acids are often referred to as the building blocks of proteins.
Although more than 100 amino acids occur naturally, only 20 are
usually involved in the synthesis of protein – and humans can
synthesize at least 100,000 different proteins. The 20 amino acids
have the same backbone, but each has a separate side chain – known
as an R-group – that distinguishes it from the others.
Antibody
A protein produced by the immune system that helps
the body fight a particular disease or develop an immunity to
it. The human body is capable of generating more than a trillion
different antibodies.
Base pair
The basic units of DNA and RNA, base pairs are
chemical structures made up of the chemicals adenine, thymine,
guanine and cytosine, which are designated by the letters A, T,
G and C, respectively. Adenine always pairs with thymine and guanine
always pairs with cytosine, creating the pairs or nucleotides
in which genetic information is found.
Cell
The basic unit of any living organism. It is a
small, watery compartment filled with chemicals and a complete
copy of the organism's genome.
Chromosome
One of the threadlike "packages" of genes and
other DNA that is compressed and wrapped around protein in the
nucleus of a cell. Different kinds of organisms have different
numbers of chromosomes. Humans have 23 pairs of chromosomes, 46
in all.
DNA
Deoxyribonucleic acid. The material inside the
nucleus of a cell that carries the genetic instructions for making
living organisms.
Double helix
The spiraling lattice of double-stranded DNA that
contains the genetic information pertinent to the organism. The
sides of the lattice – its spine – are composed of sugar and phosphate
molecules. The crosspieces, or rungs, are made up of base pairs,
also known as nucleotides.
Gene
The basic unit of heredity, the gene contains
the functional and physical characteristics passed from parent
to offspring. Genes are pieces of DNA, and most genes contain
the information for making a specific protein.
Gene mapping
The process of determining the positions of genes
on a chromosome and the distance between them.
Gene therapy
The introduction of healthy genetic material to
replace, augment or influence genes that do not function properly.
In some cases the material can be injected with what is known
as a genetic vaccination. In other cases the material is introduced
through bioengineered viruses that carry the therapeutic gene
to the cell. Globules known as liposomes can also be used to carry
therapeutic genes to specific cells.
Genetic code
The instructions in a gene that tell the cell
how to make a specific protein. A, T, G and C are the "letters"
of the DNA code; they stand for the chemicals adenine, thymine,
guanine and cytosine, respectively, which are the basic chemical
units of DNA. Each gene combines the four chemicals in various
ways to spell out 3-letter "words" that specify which amino acid
is needed at every step in making a protein. The precise order
that spells out these "words" is the genetic code.
Genome
All the DNA in an organism, including its genes.
The DNA is found as tightly coiled threads in the nucleus of every
cell. The threads are composed of paired strands of nucleotides
or base pairs. There are 3.2 billion base pairs in the human genome
and 80,000 to 100,000 genes.
Mutation
A permanent structural alteration in DNA. In most
cases such DNA changes either have no effect or cause harm. Occasionally,
however, a mutation can improve an organism's chance of surviving
and passing the beneficial change on to its descendants.
Nucleus
The central cell structure that houses the chromosomes.
Protein
A large complex molecule made up of one or more
chains of amino acids. Proteins perform a wide variety of activities
in the cell.
RNA
Ribonucleic acid. Sometimes confused with DNA,
RNA is a group of nucleic acids that along with DNA comprises
the genetic material of the cell. Genetic information is stored
by DNA in the nucleus of cells, and RNA carries that information
to other parts of the cell where it is converted into protein.
Sequencing
The process of identifying the order in which
chains of repeating units of base pairs appear in DNA and identifying
the order of amino acids in proteins. Researchers label copies
of a DNA sequence with fluorescent markers, then run them through
a sequencing machine. In proteins, amino acids are removed one
at a time from the end of a protein and identified with an automated
system.
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