Bell Work ActivityCopy onto your ‘Bell work’ paper the following question. Answer it and save it to turn in. If you don’t know an answer, get a book and find it or review with a friend. Blanks will count against you and wrong answers don’t help you.

Complete: Word association. Use the description that best describes the term. This is practice for your vocab quiz.

Agenda: Discussion: Section 1: Gregor Mendel - Quick Lab: Mendel’s Ratios

Discovery Question

• How can uniqueness contribute to scientific advancement?

Albinism

Freckles

These are examples of “Mendelian” traits. It’s through the study of dominant-recessive traits that scientists have been able to unlock the mysteries of heredity…what this chapter is dedicated to.

Do you have a physical trait or feature that is unique to just you? Maybe something that no one in your family has, or even more unique, no one at school has? Share these!

They make you special.

Genetics…studying the stuff that makes us.

• Do you have any idea how you are made the way you are?

• You’re hair color, your eye color, your height…these are all a result of how your parents genes interact with each other. You have had an idea about this, but do you know how to predict it?

• What happens when something completely unexpected happens, like disease?

• There are rules that govern this process…it’s not completely unpredictable and because of our understanding of genetics someday humans will know exactly how to custom make babies, free of disease and designed to be genetically perfect.

• In this chapter you will start to learn the process.

What Happened Here?

Impacts, Issues: The Color of Skin• Like most human traits, skin color has a genetic

basis; more than 100 gene products affect the creation and influence of melanin.

Dad:Mom: EuropeanDad: African American

Mom:Mom: EuropeanDad: African American

Fraternal Twins

The Main Objective of Genetics

• If there is one thing you should learn is being able to accurately predict the probability that something will happen.

• More specifically, you should be able to predict the likelihood that offspring from a mating will have & or display particular traits.

Objectives Section 1• Identify Gregor Mendel’s contribution to modern genetics.

• Differentiate between a character/gene and a trait.

• Describe why garden pea plants are good subjects for genetic experiments.

• Summarize the three major steps of Mendel’s first experiments.

• State the typical ratio of traits in Mendel’s first experiments.

Vocabulary

• Character• Trait• Hybrid (cross)• Generation

Mendel’s Breeding Experiments• Recall, the science of heredity and the mechanism by

which traits are passed from parents to offspring is called genetics.

• This field was undiscovered until an Austrian monk named Gregor Mendel did breeding experiments in the 1800s with the garden pea plant.

• The point…• Mendel is important to study because• Modern genetics is based on Mendel’s explanations for

the patterns of heredity in garden pea plants.

• Just as in all sound scientific experiments, Mendel practiced good techniques to ensure that his experiments gave results that were valid and useful.– He made observations that made him ask

questions.

– He made predictions.

– He designed experiments with controls.

– He kept extremely accurate records of data.

– He calculated results based upon the data.

– He proposed a theory to why everything happened the way it did based upon his results…

– And then he experimented some more!

Why Mendel’s The Bomb

Features of Pea Plants

• Mendel used pea plants as his subjects of his heredity experiments.

• The garden pea plant is a good subject for studying heredity because the plant has:

(Leave several lines below each heading.)• 1. contrasting traits,

• 2. usually self-pollinates,

• 3. and grows easily.

• We’ll take a closer look at all of these topics.

Features of Pea Plants; Contrasting Traits• Just like in modern genetics, Mendel had to study

the blending of traits that resulted from fertilizations.

• The categories of traits that are inherited are called characters.

• The different versions or forms of the characters are called traits.

• The crossing between parents with unlike traits is called a hybrid cross.

7 Characters with Contrasting Traits Studied by Mendel

THE CHARACTERS

THE TRAITS

Contrasting TraitsPea plant characters Pea plant traits

Flower Color Purple v White

Pea Color Green v Yellow

Dog characters, (aka genes) Dog traits

Hair Length Short v Medium v Long

Hair color Brown v Black v White v Yellow…

This Applies to Other Animals as Well.

Features of Pea Plants; Self-Pollination

• In garden pea plants, each flower contains both male and female reproductive parts. This arrangement allows the plant to self-pollinate = to fertilize itself.

• Cross-pollination occurs when pollen from the flower of one plant is carried by insects or by other means to the flower of another plant.

• Mendel cross-pollinated pea plants by removing the male parts from some of the flowers then dusting the female parts with pollen from another plant.

Cross-Pollination. The Process Mendel Used

Features of Pea Plants; Easy to Grow

• The garden pea is a good subject for studying heredity because it matures quickly and produces many offspring.

• Why is this good?

• You can compare many offspring to get good data!

Mendel’s First Experiments

• Mendel’s first experiments used monohybrid crosses and were carried out in three steps.

• A monohybrid cross is a cross that is done to study one pair of contrasting traits. – Crossing a plant that has purple flowers with a plant that has

white flowers is an example of a monohybrid cross.

• Each step involved a new generation of plants. A generation is a group of offspring from a given group of parents.

A Monohybrid Cross

A monohybrid cross means to mate two flowers.In Mendel’s case he chose two with contrasting traits.Parents = p generation1st generation = F1

OFFSPRING1st Generation

3 Steps Mendel’s First Experiments, continued

1st Step: Producing the Parental (P) generation• Plants that self-pollinate for several generations

eventually produce offspring of the same trait. Such a plant is said to be true-breeding for a given trait.

• The first group of parents that are crossed in a breeding experiment are called the parental generation or P generation.

• Mendel first produced true-breeding plants for the P generation.

• Using true-breeding plants ensured that the traits being studied were predictable (free of variables).

2nd Step: Producing the F1 Generation• The true-breeding P generation were cross-

pollinated, producing offspring.

• The offspring of the P generation is called the first filial generation, or F1 generation.

• He then recorded the traits of this generation.

3 Steps Mendel’s First Experiments, continued

3rd Step: Producing the F2 Generation• Mendel allowed the F1 generation to self-

pollinate and produce new plants.

• He called this offspring the second filial generation, or F2 generation.

• He then recorded data about the F2 generation.

3 Steps Mendel’s First Experiments, continued

Visual Concept: Mendel’s Experiments

Mendel’s Results

• All of Mendel’s F1 (first generation) plants expressed the same trait for a given character. The contrasting trait seemed to have disappeared.

• The contrasting trait reappeared, however, in some of the F2 plants when the F1 plants were allowed to self-pollinate. But, most importantly, the traits appeared in a predictable pattern.

• For each of the seven characters that Mendel studied, he found a predictable 3-to-1 ratio of contrasting traits in the F2 generation. – This lays the groundwork for dominant and recessive traits…

Mendel’s Crosses and Results

Summary• Modern genetics is based on Mendel’s explanations for the patterns

of heredity that he studied in garden pea plants.

• The garden pea plant is a good subject for studying heredity because the plant has contrasting traits, usually self-pollinates, and grows easily.

• Mendel’s first experiments used monohybrid crosses and were carried out in three steps.

• For each of the seven characters that Mendel studied, he found a similar 3-to-1 ratio of contrasting traits in the F2 generation.

Application• Calculating Ratios

• Mendel obtained data from his experiments but to get an idea of what the data was telling him he had to work with the numbers.

• He chose ratios because using ratios is a way to compare different values.

• Conduct the “Quick Lab” on page 270.

• Compare the number of boys to girls by Calculating the ratio of boys to girls in the class.

• Amount of one (first value) Amount of the other (second value)

• Then simplify.

• Why simplify?• Let’s say you have 45 sodas and 8 people. How

many sodas can each person have?...• This let’s you know a lot of comparative info.

First Review: Calculating Ratios

HW/CW

• Practice reproducing the ratios Mendel formed by completing the “Quick Lab” on page 270. – This is your first lab… 25 pts due 1/31