1. Heredity and Mendel
EQ: How do genes and chromosomes work together to determine an organism’s traits?

2. Why don’t you look like a rhinoceros?
The answer seems simple --- neither of your parents is a rhinoceros (I assume).
But there is more to this answer than meets the eye.
We look similar to our parents because of heredity.

3. Heredity
Heredity is the process of passing characteristics or traits, such as eye color, skin, color, hair, color, height, intelligence, etc. from parent to offspring.
This happens during reproduction

4. Passing Along Traits
When organisms reproduce, they create new offspring.
These offspring receive traits from both the female and the male parent.

5. Passing Along Traits
As you may have guessed, the passing of traits from parent to offspring is complicated….
For example:
Why do I have straight hair while both of my parents have curly hair?
How did my husband and I produce a left-handed child when we are both righties?
How did my two nephews end up with blue eyes when both of their parents have brown eyes?

6. Apparently we aren’t the only ones who wonder!
About 150 years ago, an Austrian monk named Gregor Mendel started performing important experiments that helped scientists figure out the answers to such questions.

7. Gregor Mendel
Gregor Mendel was born in 1822 and grew up on a farm in Austria.
While growing up on the family farm, Mendel observed and learned a lot about flowers and fruit trees.
But it was not until he was working in the monastery’s garden that he began his research on patterns of inheritance

8. Gregor Mendel
Mendel knew that patterns of inheritance were not always clear.
He saw that sometimes a trait that was apparent in one generation (parents) was not present in the next generation (offspring).
In the next generation, the trait showed up again.
Mendel wanted to know why

9. Self-Pollinating Peas
To start unraveling this mystery, Mendel selected to study the inheritance pattern of garden peas.

10. He actually had good reasons for selecting peas
They grow quickly
They are able to self-pollinate
Plants contain male and female structures and can pollinate themselves.
They will be true breeding plant
All offspring will have the same trait as their parents
They are also able to cross-pollinate
The pollen of one plant can pollinate another plant and carry traits from one plant to another

11. Characteristics Mendel only studied one characteristic at a time
A characteristic is a feature that has different forms in a population
For example, hair color is a characteristic
These different forms are called traits.
The different forms of hair color are brown, blond, red, etc.
Mendel used plants that had different traits for each of the characteristics he studied.
Characteristic: seed shape Trait: wrinkled, round
Characteristic: Plant height trait: Tall, short
Characteristic: Flower color Trait: purple, white

12. Gregor Mendel
Mendel was careful to use plants that were true breeding for each of the traits he was studying.
By doing this, he would know what to expect if his plants were to cross-pollinate.
He decided to find out what would happen if he bred, or crossed two plants that had different traits of a single characteristic
Example: cross a purple flowered plant with a white flowered plant

13. Gregor Mendel
In his first experiments, Mendel crossed pea plants to study seven different characteristics.
He used true-bred plants
For example, he crossed plants that had purple flowers with plants that had white flowers.
All of the plants that resulted had purple flowers!

14. Gregor Mendel Mendel got similar results for each cross
One trait that was always present in the first generation, such as white flowers, seemed to disappear.
Mendel chose to call the trait that appeared the dominant trait.

15. Dominant Traits
Dominant traits are the traits that will appear in the offspring if one or both of the parents contributes it.
Examples:
Brown eyes
Dark hair
Dimples
Curly hair
Freckles
Extra digits
Normal hearing

16. Recessive Traits Examples: Grey, green, hazel, blue eyes Blond hair
Red hair
Straight hair
No freckles
Normal number of digits
deafness
Because the other trait seemed to recede into the background, Mendel called it the recessive trait.
Recessive traits are traits that must be contributed by both parents in order to appear in the offspring.
Recessive traits can be carried in a person's genes and not appear on that person

17. Mendel’s Second Experiment
In his second experiment, Mendel allowed the first generation plants to self-pollinate
He found that even when purple flowered plants crossed with white flowered plants, all of the flowers were purple, showing that purple flowers were the dominant trait.

18. Mendel’s Second Experiment
However, in the second generation, for every three purple flowered plants, there was one white flowered plant, showing that the recessive gene was present.

19. Gone, but not forgotten In 1865, Mendel published his findings.
But they were not understood or accepted until many years after his death.
Once his research was understood, the door was opened to modern genetics.
Genetic research is one of the fastest changing fields in science today. #

20. Dominant and Recessive Traits
EQ: How do genes and chromosomes work together to determine an organism’s traits?

21. Traits
A trait is a distinguishing characteristic that an organism can pass to its offspring.
A gene is unit of hereditary material that determines traits
For most traits, there are two forms of the same gene.
An allele is one of a number of different forms of a particular gene

22. Traits
Organisms have at least two alleles for each gene --- one from each parent
The dominant allele is the form of a gene, that, when present covers up the appearance of the recessive allele
The recessive allele is the form of a gene that is hidden when the dominant allele is present
Recessive alleles can be carried in a person's genes and not appear on that person!

23. Today’s Activity: Dominant and Recessive Traits
Each group will investigate dominant and recessive alleles by taking an inventory of the population of Crazy Creatures
After analyzing the data collected, each group will deduce the basic patterns of inheritance as discovered by Gregor Mendel
Materials
Activity Sheet (per person, white paper)
Crazy Creature face packet (per group, colored paper)
Blue (egg) coin
Green (sperm) coin

24. Today’s Activity: Dominant and Recessive Traits
Directions overview: As a table, you are expected to read and follow the detailed directions on your activity sheets!
Collect the data
Examine the creature faces on the colored sheet, count and record how many organisms you find with each form of the highlighted traits
DO NOT WRITE ON THE COLORED SHEET
Develop a model
Answer questions 4c-4i collaboratively
See me when you get to question 4h!
Explore on your own
Use the blue (egg) and green (sperm) coins to determine the ear shape of a sample population of creatures
The coins are in cups on the back counter. When it’s time, send ONE person to pick up your table’s cup
Draw your results on the circles below the instructions