Glossary
Base Sequence
The specific order of nitrogenous bases (A, T, C, G in DNA; A, U, C, G in RNA) along a nucleic acid strand. This sequence encodes the genetic information.
Example:
A change in just one letter of the base sequence can lead to a genetic mutation, like in sickle cell anemia.
Chromosomes
Structures found in the nucleus of eukaryotic cells, consisting of DNA tightly coiled around proteins. They organize and carry genetic information.
Example:
Humans typically have 23 pairs of chromosomes, with one set inherited from each parent.
Complementary Base Pairing
The specific pairing of nitrogenous bases in nucleic acids: Adenine (A) with Thymine (T) in DNA (or Uracil (U) in RNA), and Cytosine (C) with Guanine (G). This rule is fundamental for DNA replication and transcription.
Example:
During DNA replication, the enzyme DNA polymerase uses complementary base pairing to add the correct new nucleotides to the growing strand.
DNA (Deoxyribonucleic Acid)
The primary genetic material in most organisms, forming a double helix structure. It carries the instructions for an organism's development, functioning, growth, and reproduction.
Example:
Your unique eye color and hair texture are determined by the specific sequence of bases in your DNA.
Plasmids
Small, circular, double-stranded DNA molecules found in the cytoplasm of many prokaryotic cells, separate from the main bacterial chromosome. They often carry genes that provide advantageous traits, like antibiotic resistance.
Example:
Bacteria can share genes for antibiotic resistance by transferring plasmids to one another, making them harder to treat.
Purines
Nitrogenous bases characterized by a double-ring structure. In DNA and RNA, these include Adenine (A) and Guanine (G).
Example:
In the DNA double helix, a purine like Adenine always pairs with a pyrimidine like Thymine, maintaining the consistent width of the molecule.
Pyrimidines
Nitrogenous bases characterized by a single-ring structure. In DNA, these include Cytosine (C) and Thymine (T); in RNA, Uracil (U) replaces Thymine.
Example:
The pyrimidines Cytosine and Thymine are essential components of the genetic code, forming specific pairs with purines.
RNA (Ribonucleic Acid)
A single-stranded nucleic acid that plays crucial roles in gene expression and protein synthesis. It uses uracil (U) instead of thymine (T).
Example:
When a cell needs to make a protein, a messenger RNA molecule carries the genetic code from the DNA to the ribosomes.
Sugar-Phosphate Backbone
The structural component of DNA and RNA, formed by alternating sugar and phosphate groups linked by phosphodiester bonds. It provides stability to the nucleic acid strand.
Example:
The strong covalent bonds forming the sugar-phosphate backbone protect the delicate nitrogenous bases within the DNA helix.