ScienceVerseLearning path: Genes
The concepts to learn before Genes, in order. Each step links to its page and, where one exists, its quiz.
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Your path
- DNADirect prerequisite
Deoxyribonucleic acid: the molecule that carries the genetic instructions used in the growth, development and reproduction of all known living organisms. DNA is shaped as a double helix of two strands, each made of a sugar-phosphate backbone with attached bases — adenine (A), thymine (T), guanine (G) and cytosine (C) — that pair specifically (A with T, G with C) to hold the two strands together. Its structure was determined by James Watson and Francis Crick in 1953, building on X-ray diffraction data produced by Rosalind Franklin and Maurice Wilkins.
- GenesYour goal
A gene is the basic physical and functional unit of heredity: a stretch of DNA that carries information a cell can use. Many genes hold the instructions for making a protein, which the cell reads in two steps — transcription into messenger RNA, then translation into a chain of amino acids — while many others make no protein and instead help control other genes. People usually carry two copies of each gene, one from each parent, and slightly different versions of a gene are called alleles.
Where to go next
Concepts that build directly on Genes:
- Inheritance: Inheritance is how genetic information passes from parents to offspring. Working with garden peas in the 1850s and 1860s, Gregor Mendel showed that traits are passed on as discrete units — what we now call alleles of genes — rather than blending together, and that a cross between two heterozygotes gives a predictable 1:2:1 genotype ratio and, under complete dominance, a 3:1 phenotype ratio. A Punnett square turns those rules into expected offspring frequencies.