Day 18-DNA

1. Mendel designed an experiment involving crossbreeding pea plants. He bred different variations of the plants, such as tall and short plants. In his findings, he proved that heritable variants are not just blended randomly, but are "discreet entries passed from parents to offspring."  
2. Francis Crick and James Watson discovered the double-helix structure (see image below).
3. Variations:
• Point Mutation- Inactivates the gene, such as in whippet dog, which has a much more slender body than most other dogs.
• Insertion- A new base-pair is inserted into the gene, such as pea plants which have wrinkled skin instead of smooth skin. 
• Gene Copy Number- When entire genes are duplicated, such as in chimps, who have only 1 enzyme to digest green plants where as humans have 10.
• Duplication- Sequences containing 8 or more of the same base-pair, which can cause dark spots on the body.
• Regulatory Changes- A mutation which turns genes on and off, which can cause appearance changes.
4. Evo-devo is the study of the role that the effects of changes in important developmental genes play in evolution. 
5. If a person stops drinking milk after their infant years, they will loose the enzyme which allows them to digest lactose. Those who do not stop, though, will have an enzyme called lactase, which allows them to drink milk.