Glossary Terms: A - D

Terms

  1. Allele

  2. Autosomes

  3. Base

  4. Cell

  5. Chromosome

  6. Darwin, Charles

  7. DNA (Deoxyribonucleic Acid)

  8. Double Helix

Definitions

  1. Allele

    Variant form of a gene

  2. Autosomes

    The 22 pairs of recombining chromosomes in the cell nucleus, which, along with the X and Y sex chromosomes, make up the nuclear genome

  3. Base

    The chemical building blocks of DNA. Named A, T, C, and G (adenine, cytosine, thymine, and guanine), these bases pair up to form the “stairs” of the DNA double helix and always combine in the same patterns: A with T and C with G.

  4. Cell

    The smallest unit of living matter that can operate independently

  5. Chromosome

    Long strands of DNA on which genes are found. Each human cell has 46 chromosomes in 23 pairs. One member of each pair is inherited from the mother, the other from the father.

  6. Darwin, Charles

    Charles Darwin’s 1859 book The Origin of Species promoted a theory of evolution by natural selection and challenged Victorian-era ideas about the role of humans in the universe. Darwin’s theories were based on a constantly evolving natural world and held that each generation of a species had to compete for survival. Survivors held some natural advantages over their less fortunate relatives and passed those characteristics on to their progeny, thus over-representing these favored genetic types in the next generation. Darwin also advanced the idea that species were descended from a common ancestor. Darwin’s work became the foundation of modern evolutionary theory.

  7. DNA (Deoxyribonucleic Acid)

    The double helix-shaped molecule that holds an organism’s genetic information. DNA is composed of sugars, phosphates, and four nucleotide bases: adenine, guanine, cytosine, and thymine (A, G, C, T). The bases bind together in specific pairs.

  8. Double Helix

    The shape of DNA, similar to that of a spiral staircase or twisted ladder. The stairway’s railings are composed of sugars and phosphates. Its sides contain the patterned base pairs: A, T, C, and G. When a cell divides for reproduction, the helix unwinds and splits down the middle like a zipper in order to copy itself.

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