ALLELE One of the possible alternative forms of a gene, often distinguished from other alleles by phenotypic effects.
AMINO ACIDS Aminocarboxylic acids comprising the subunits covalently linked to form proteins.
CHROMATIN The complex of DNA, RNA, histones, and nonhistone proteins that make up uncoiled chromosomes, characteristic of the eukaryotic interphase nucleus.
CODON A triplet of messenger RNA (mRNA) nucleotides that specifies a particular amino acid or a start or stop signal in the genetic code. Sixty-one codons specify the amino acids used in proteins, and three codons, called stop codons (UAG, UAA, UGA), signal termination of growth of the polypeptide chain. One codon (AUG) act as a start codon in addiction to specifying an amino acid.
DNA is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.
GAMETE is a haploid cell that fuses with another haploid cell during fertilization in organisms that sexually reproduce.
GENOME is the totality of genetic material carried by an organism.
EXON The DNA segments of a gene that contain the sequences that, through transcription and translation, are eventually represented in the final polypeptide product.
HEMOPHILIA An X-linked trait in humans that is associated with defective blood-clotting mechanisms.