THE GENETIC BASIS of INHERITING A TRAIT

First, some terminology Trait: a physical characteristic caused by genetics. Here are some examples: Eye colour Hair colour Ability to digest lactose Mental disabilities Genetic disorders or diseases, etc. Plants: Flower colour Plants: Seed size. Generation: Each of the following is one human generation Great-grandparents Grandparents Parents Children Offspring: A parent’s child, an animal’s young, a plant’s “next generation,” etc. Heredity: the passing of traits from parents to offspring.

SELECTIVE BREEDING The process by which humans choose specific members of an organism’s population to breed together - producing offspring with favourable characteristics. Labrador Retriever Gentle, easy to train, service dog. Poodle Highly intelligent, doesn’t shed a lot of fur, good for people with allergies. Labradoodle

MORE SELECTIVE BREEDING EXAMPLES Corn Bananas Tomatoes These changes have taken hundreds to thousands of generations to happen!

Humans have used selective breeding for thousands of years. Most selective breeding involved food production: Corn: Breed large “husks” with other large “husks”  more corn to eat. Bananas: Breed less “seedy” bananas with other less “seedy” bananas  seedless bananas. Tomatoes: Breed tomato plants with large fruit with other tomato plants with large fruits  more tomato to eat! Livestock (Eg. Chickens): Breed the largest and healthiest chickens with each other  more protein. They knew it worked, but had no idea WHY! Until Gregor Mendel figured it out!

GREGOR MENDEL & HIS EXPERIMENTS He experimented with Pea Plants to figure out how traits were passed on from generation to generation. He found that Pea Plants can either self-fertilize or cross-pollinate.

GREGOR MENDEL & HIS EXPERIMENTS 1.First step: Control group When purple-flowered plants were self- fertilized, all of the offspring had purple flowers. When white-flowered plants were self- fertilized, all of the offspring had white flowers. That was expected…

GREGOR MENDEL & HIS EXPERIMENTS 2. Second step: Cross-breeding Mendel crossed white-flowered plants with purple-flowered plants. What colour(s) do you think the next generation will be? (What is your hypothesis?) A)All flowers will be white flowers B)All flowers will be purple C)All flowers will have a solid colour of light purple D)All flowers will have white and purple “splotches”

Result: ALL PURPLE! What happened to the white flower?!

GREGOR MENDEL & HIS EXPERIMENTS 3. Third Step: Purple + Purple Mendel allowed the 100% purple-flowered plants to reproduce with each other. The White Flower Came Back!