Supplementary Document S10: Glossary
Allele: different forms of the same gene. According to the Mendelian concept of a gene, a gene
is an inherited factor controlling the phenotype of a trait, and alleles are copies of genes with
some modification that alters this phenotype in some way. Alleles are detected only when the
differences in phenotype can be detected.
Alternative splicing: a process by which post-transcriptional pre-mRNA processing can result
in different proteins (isoforms) from the same coding locus. RNA splicing of the primary
transcript using different exons to produce different mRNAs, which in turn give different
proteins during translation.
Autosome: All chromosomes except the sex chromosomes In humans, chromosomes 1-22 are
autosomes.
Base: Either a purine or a pyrimidine, usually linked to a ribose or deoxyribose and a component
of DNA and RNA.
Base pair: Formed when complementary nucleotides pair by hydrogen bonding. In DNA, the A
nucleotide bonds with T, and G bonds with C. Base pairs form the "rungs" of the DNA ladder
and the number of base pairs in a strand can be used to describe the length of DNA.
Centromere: A region of hte chromosome where the spindle fiber attaches to allow segregation
of chromosomes during meitoic and mitotic cell divisions and does not divide until the beginning
of anaphase. This region is referred to as the CEN region; in yeast it is about 250bp long and is
composed of three regions of conserved sequences.
Chromosome: A densely staining cellular entity, composed of DNA complexed with proteins.
Chromosomes contain, or consist of, a linear sequence of genes.
Deoxyribonucleic acid (DNA): The genetic material of most organisms. DNA is a long doublehelical molecule composed of the deoxyribonucleotides-deoxyadenylic acid (A), dexythymidylic
acid (T), deoxyguanylic acid (G), and deoxycytidylic acid (G). The two strands are held together
by hydrogen bonds between A:T and G:C pairs.
Diploid: An individual or cell with two sets of chromosomes.
Double helix: In DNA, two polynucleotide strands running in opposite directions (one is 5' to 3'
and the other 3' to 5') to form a double-stranded molecule that takes a helix formation. A helix is
a spiral turning in a left-handed manner or a right-handed manner.
Gene: A hereditary determinant of a specific biological function located at a fixed position on a
chromosome. A gene can be defined either genetically or physically. In physical terms, the gene
is defined as the coding region of DNA that determines a protein product.
Genome: A complete set of chromosomes, genes, or genetic information in a cell or organism
inherited as a unit from a parent(s).
Genotype: The total set of genes in an organism; The genetic makeup, as distinguished from the
physical appearance, of an organism or a group of organisms.
Haploid: One complete set set of chromosomes (n),present in the egg and sperm cells of animals
and in the egg and pollen cells of plants. Humans have 23 chromosomes in their sex cells (n=23).
Homologous chromosomes: A pair of chromosomes that resemble each other and have nearly
the same DNA sequence. One comes from the male parent and the other, from the female parent.
Homologous recombination: Recombination between two chromosomes that have extensive
sequence identities (the sequence of DNA is highly similar).
Meiosis: Two cell divisions that reduce the number of chromosomes by half; the process that
produces haploid gametes.
Mitosis: The process of nuclear division in eukaryotes that produces two identical daughter
nuclei.
Mutation: Alteration in the DNA sequence of an allele; an inherited genetic change.
p-arm: The short arm of a human chromosome. The p- and q-arms of a chromosome are
separated by the centromere.
Phenotype: The physical characteristics of an organism. Individuals carrying different sets of
alleles will have different physical characteristics, or phenotypes.
q-arm: The long arm of a human chromosome. The p- and q-arms of a chromosome are
separated by the centromere.
Recombination: The reassortment of genes in new combinations following exchange of DNA
sequences.
Sex chromosome: A chromosome pair in eukaryotes that usually differ in size and shape and
control sex determination. The presence of identical pairs is usually present in the female and
nonidentical pairs in males (the case in humans), although the reverse also occurs (for instance,
in birds).
Sex-linked trait: A trait that is located on the sex chromosome and is phenotypically present in
the the heterogametic sex when recessive. For example, the gene for red-green color vision in
humans is located on the X chromosome; males with the mutated form of the gene present on
their single X chromosome will express the colorblindness phenotype, whereas females require
would require the mutated gene to be present on both of their X chromosomes to express the redgreen colorblindness disease phenotype.
Telomere: The terminal region of a chromosome that prevents random fusions to other
chromosomes. Telomeres are composed of repeated DNA sequences and are associated with the
replication and stability of linear chromosomes, like those in most eukaryotes.