Chromosomes, Genes & DNA
Describe the relationship between chromosomes, genes, and DNA in heredity, including the double helix structure of DNA and the historical roles of Watson, Crick, Franklin, and Wilkins
What a learner can do afterwards
- Explains the hierarchy: DNA → gene → chromosome → nucleus → cell
- Describes what a gene is and what it codes for
- States that human body cells contain 46 chromosomes in 23 pairs
- Describes the contributions of Watson, Crick, Franklin, and Wilkins to the discovery of DNA structure
The lesson
Every cell in your body has a nucleus, and inside that nucleus is a long molecule called DNA. DNA is not loose and messy. It is coiled up tightly into structures called chromosomes.
A gene is a short section of DNA. Each gene carries the instructions for one particular trait, such as eye colour or blood type. Thousands of genes strung together along a coiled strand of DNA make up one chromosome.
A skin cell and a nerve cell from the same person both carry the same 46 chromosomes, arranged in 23 pairs. One chromosome in each pair came from your mother, and one came from your father.
DNA is shaped like a twisted ladder, called a double helix. Rosalind Franklin's X-ray images gave the first clear evidence of that shape. James Watson and Francis Crick used her data, shared by Maurice Wilkins, to build the model scientists still use today.
DNA holds genes, genes are strung along chromosomes, and a human body cell holds 46 chromosomes in 23 pairs.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.