GREGOR MENDEL Gregor Mendel ( ) was an Austrian monk who studied genetics. - Heredity in plants Gregor Mendel ( ) was an Austrian monk who studied genetics. - Heredity in plants What is heredity? Heredity is the passing down of traits from one generation to another.

Mendel’s Observations Mendel made many observations about pea plant characteristics. Mendel made many observations about pea plant characteristics.

Mendel’s Observations Mendel’s Observations Mendel’s first series of observations included both tall and short plants. Mendel’s first series of observations included both tall and short plants. He assumed that there would be equal amounts of each plant size if they were crossed or mated. He assumed that there would be equal amounts of each plant size if they were crossed or mated.

Mendel’s Pea Plant Experiment Why did Mendel chose to study pea plants? Why did Mendel chose to study pea plants? How did he make the plants reproduce? How did he make the plants reproduce?

What did Mendel do? Mendel crossed a tall plant and a short plant. Remember: Mendel thought that the offspring would be half tall and half short. Actually, all the offspring were tall! P Generation F 1 Generation

Then what did Mendel do? Mendel then performed a self-cross within the offspring generation. Mendel then performed a self-cross within the offspring generation. This time, 75% of the offspring were tall and 25% were short. This time, 75% of the offspring were tall and 25% were short. Where did the short plant come from??? Where did the short plant come from??? F 1 GenerationF 2 Generation

RECAPRECAP

Characteristics vs. Traits A characteristic is the category of traits A characteristic is the category of traits Hair Color is a Characteristics Hair Color is a Characteristics A trait is a type of the characteristic A trait is a type of the characteristic Brown, Red, or Blonde Hair are Traits Brown, Red, or Blonde Hair are Traits

What did Mendel conclude? Mendel's observations from these experiments can be summarized in two principles or laws: Mendel's observations from these experiments can be summarized in two principles or laws: 1. The Law of Segregation 2. The Law of Independent Assortment

Law of Segregation An organism has two types of each trait. Only one is passed on to the next generation. An organism has two types of each trait. Only one is passed on to the next generation. Which trait is passed on is a matter of chance. Which trait is passed on is a matter of chance. This segregation of traits occurs during the process of sex cell formation This segregation of traits occurs during the process of sex cell formation

Independent Assortment Alleles for different traits are passed to offspring independently of each other. Alleles for different traits are passed to offspring independently of each other. Here are two examples to clear this up: Here are two examples to clear this up: A pea plant having purple flowers does not mean the pea plant is tall. A pea plant having purple flowers does not mean the pea plant is tall. Likewise, the principle of independent assortment explains why a person with brown hair does not always have dimples. Likewise, the principle of independent assortment explains why a person with brown hair does not always have dimples.

Independent Assortment Question: Can you think of any exceptions to the law of independent assortment? Question: Can you think of any exceptions to the law of independent assortment? Why do most people with red hair have freckles? Why do most people with red hair have freckles? Why do most people with (natural) blonde hair have light colored eyes? Why do most people with (natural) blonde hair have light colored eyes? Answer: Some genes are very close to each other on the chromosome. Therefore, when one gene is passed down, chances are, so will the other one. Answer: Some genes are very close to each other on the chromosome. Therefore, when one gene is passed down, chances are, so will the other one.