Genetics and Molecular Biology

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DNA (Deoxyribonucleic Acid)

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The primary carrier of genetic information in most organisms, a double-stranded molecule composed of nucleotides.

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Nucleotide

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The monomer unit of nucleic acids (DNA and RNA), consisting of a phosphate group, a five-carbon sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base.

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Nitrogenous Base

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A component of a nucleotide that carries the genetic code. In DNA, these are Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). In RNA, Thymine is replaced by Uracil (U).

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Base Pairing Rules

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The specific interactions between nitrogenous bases in nucleic acids: Adenine (A) pairs with Thymine (T) in DNA (and Uracil (U) in RNA), and Cytosine (C) pairs with Guanine (G).

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Double Helix

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The characteristic twisted ladder structure of a DNA molecule, formed by two complementary strands of nucleotides held together by hydrogen bonds between the base pairs.

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Gene

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A segment of DNA that contains the instructions for building a functional product, usually a protein.

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Protein

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A complex macromolecule made of amino acids linked together. Proteins perform a wide variety of functions in living organisms.

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Gene Expression

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The process by which the information encoded in a gene is used to direct the assembly of a protein molecule or a functional RNA molecule.

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Transcription

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The process in the nucleus where the DNA sequence of a gene is copied into a complementary messenger RNA (mRNA) molecule.

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mRNA (Messenger RNA)

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A type of RNA molecule that carries the genetic information from DNA in the nucleus to the ribosomes in the cytoplasm for protein synthesis.