DNA, Genes, and Genetics

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DNA (deoxyribonucleic acid) is an organic chemical of complex molecular structure that is found in all prokaryotic and eukaryotic cells and in many viruses. DNA codes genetic information for the transmission of inherited traits.

Genes are the units of hereditary information. They occupy a fixed position on a chromosome and contain the genetic code used in the synthesis of proteins.

Genetics is the study of heredity in general and of genes in particular.

-- 1, 2

The genotype is the set of genes which are responsible for a particular trait. The phenotype is the physical (observable) expression of that trait. For example, two organisms that have even the smallest difference in their genes have different genotypes. They may, however, have the same phenotype.

The phenotype is influenced both by the genotype and by the environment.


On-line copies of handouts for reading worksheets.

  • Genetics
    • 10.1 - Mendel's Laws of Heredity
    • 10.2 - Meiosis (extra credit)
    • 11.1 - DNA: The Molecule of Heredity
    • 11.3 - Genetic Changes
    • 12.1 - Mendelian Inheritance of Human Traits
    • 12.2 - When Heredity Follows Different Rules
    • 12.3 - Complex Inheritance of Human Traits
    • 13.1 - Applied Genetics





Q & A

Chromosomes Karyotype

A *karyotype* is a systematized arrangement of chromosome pairs displayed in descending order of size.

  • Human male karyotype:

Topic revision: r14 - 29 May 2018, VickiBrown

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