Introduction

On a 3 x 5 card write down a description of yourself using only your inherited traits. For example, you can describe your hair color or texture but not your hair style that day. The description will be read aloud to the class. The class will try to figure out if they could identify the student based on the description.

11-1 The Work of Mendel• What does every living thing inherit from

their parents?• Genetics – the study of heredity

Look around at your classmates and make a list of some of the traits that are inherited.

Gregor Mendel’s PeasRead about Mendel on p. 308 – report some

findings about his life.

• What was Mendel in charge of at the monastery? Garden

• What did he grow and study? Pea Plants

What did Mendel already know …

• Each flower produces pollen and egg cells

• Cross fertilization (sexual) – male and female cells join

• Self-pollination (asexual) – pollen fertilizes eggs from same plant

• Mendel’s pea plants were true-breeding – A tall plant with green seeds would produce a

tall plant with green seeds

How Mendel started his experiment• Cross-pollinated the pea plants

• Had to prevent self-pollination in order to do this…HOW?

Cut away the male parts of the plant

• How did Mendel cross-pollinate the plants?

Dusted the female reproductive part with pollen from another plant

How Mendel started his experiment• What did cross-

pollination produce?

Hybrid Plants

• What did this make possible?

To study the inheritance of certain traits

Genes and Dominance• Trait – specific characteristic

– Mendel studied 7 different pea plant traits• What are some examples? Plant Height, Seed

Shape, Pod Color

Mendel crossed plants to study offspring• The original plants = P generation

• The offspring = F1 generation

• Hybrid – offspring of crosses btwn parents w/ diff. traits

Mendel crossed plants to study offspring

• Mendel expected a blend of traits HOWEVER

• Offspring had characteristic of one parent

• The character of the other parent seemed to disappear

Mendel crossed plants to study offspring

• Genes – the chemical factors that determine traits

• Alleles – different forms of a gene– Ex. From pea plants: gene = plant height

alleles = tall and short

Mendel crossed plants to study offspring

• Principle of dominance: some alleles are dominant and others are recessive

• Dominant allele – the trait is always shown– Capital letter

• Recessive allele – the trait that will only show if there is no dominant allele– Lower case letter

Segregation

• Mendel’s next question…Where had the recessive allele gone?

• P generation – (parents, originals) – Tall x short

• F1 generation – (offspring of P) tall x tall

• F2 generation – (offspring of F1) 3 tall, 1 short

The F1 Cross• Shows the F2 generation

• Recessive alleles had reappeared!!!

Questions1. Genetics is the study of ________.

2. Alternate characteristics of an organism such as height, hair color, eye color, etc. are called _______.

3. Why did pea plants make such a good subject for Mendel to study?

4. Pea plants are self pollinating. Why did mendel cross pollinate?

5. What does “true breeding” mean?

Considering the allele related to short and tall pea plants.

1. Plants of the P generation (tall) will produce only_____________ if not crossed with plants having other alleles.

2. Describe the phenotype (what we can see) of Mendel’s F1 Generation.

3. What was the genotype (use letters “T” and “t”) for Mendel’s F1 generation?

4. How did the F2 generation suggest that genes were simply segregated, not lost?