Mendel and His Peas

Why don’t you look like a rhinoceros?

The answer to this question seems simple: Neither of your

parents is a rhinoceros. But there is more to this answer

than meets the eye.

How are traits passed from parents to

offspring?

Do You Agree or Disagree?

1. Like mixing paints, parents’ traits always blend in their offspring.

2. If you look more like your mother than you look like your father, then you received more traits from your mother.

3. All inherited traits follow Mendel’s patterns of inheritance.

Early Ideas About Heredity

- Heredity is the passing of traits from parents to offspring.

- Gregor Mendel is known as the father of genetics — the study of how traits are passed from parents to offspring.

May Be More Complicated Than You Think!

-You might have curly hair, while both of your parents have straight hair.

-You might have blue eyes even though both of your parents have brown eyes.

HOW DOES THIS HAPPEN?!

https://www.youtube.com/watch?v=QmSJGhPTB5E

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Gregor Mendel(1822-1884)The Father of Genetics

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Gregor Johann Mendel

Austrian monk

Studied the inheritance of traits in pea plants

Developed the laws of inheritance

Mendel's work was not recognized until the turn of the 20th century

https://www.youtube.com/watch?v=Mehz7tCxjSE&feature=share

Mendel's Experimental Methods

Mendel studied genetics by doing controlled breeding experiments with pea plants.

There are two types of pollination: • self-pollination • cross-pollination

Think-Pair-Share

What do you think the difference is between self-pollination and cross-

pollination?

Self Pollination

Mendel's Experimental Methods (Con)

• When a true-breeding plant self-pollinates, it always produces offspring with traits that match the parent.

• Mendel cross-pollinated pea plants himself and recorded the traits that appeared.

Cross-Pollination

Gregor removed the anthers of the plants to make sure they did not self-pollinate.

Mendel’s Results

• Once Mendel had enough true-breeding plants for a trait he wanted to test, he cross-pollinated selected plants.

• Plants are called hybrids if they come from true-breeding parent plants with different forms of the same trait.

He Studied:

- seed shape- plant height- flower color

- 7 characteristics

First Generation Crosses

Look on page 407 in textbook.

Purple Flowers + White Flowers =

ALL PURPLE

Second Generation Hybrid Crosses

• Mendel also cross-pollinated hybrid plants.

• He observed that offspring of hybrid crosses always showed traits in a 3:1 ratio.

Second Generation Hybrid Crosses

Mendel’s Results (Cont)

Mendel recorded traits of offspring

from many hybrid

crosses.

Mendel’s Conclusions

Mendel concluded that two factors, one from each sperm and one from each egg, control each inherited trait.

Mendel’s Conclusions (cont)

• A dominant trait is a genetic factor that blocks another genetic factor.

• A recessive trait is a genetic factor that is blocked by the presence of a dominant factor.

Review Question 1

What method did Mendel use to select which plants pollinated other plants?

A) True breedingB) Self-pollinationC) Cross- pollinationD)bees

C

Review Question 2

What is the approximate ratio of dominant to recessive expression when both parents are hybrid?

A) 1 : 1B) 2 : 1C) 3 : 1D)4: 1

C

Class Work1) What is the difference between genetics and

heredity?2) Describe Mendel’s first set of experiments.3) Describe Mendel’s second set of experiments.4) Why do you think Mendel chose to study pea

plants? 5) In cats, there are two types of ears: normal and

curly ears. A curly-eared cat mated with a normal-eared cat, and all of the kittens had curly ears. Are curly ears a dominant or recessive trait? Explain.