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Imagine that you are planning to meet your pen pal but you two have never met in person.
What traits (distinguishing quality or characteristic) would you use to describe yourself? Make a list.
Which of these traits do you think you inherited? Put a check mark next to these traits on your list.

Inheriting the good, the bad, and the ugly!
The study of heredity and the variation of inherited characteristics.

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Because your parents do not have the traits of a rhinoceros!
Dogs and cats have different DNA. They are genetically different from one another.
Heredity is the passing of traits from parents to offspring.
A trait is a distinguishing quality or characteristic.
Offspring is the descendants of a person, animal, or plant considered as a group.

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Complete the Inventory of My Traits –
Survey independently
Data Table Results, as a class
Make a graph of the class results
Study the data. What trends do you observe? What heredity traits are more common among the class?

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But, what if both of your parents have straight hair, and you have curly?
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What if both of your parents have brown eyes, but you have blue?
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With your table group, develop 2-3 possible reasons for how this might happen. Write your hypotheses in your spiral.

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If a black dog and a white dog have puppies, what color will those puppies be?
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Grey?
Black?
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White?
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Half black and half white?
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A different color all together?

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The study of genetics and heredity helps us to answer these puzzling questions.
How do we study heredity?

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Early studies used plants, rather than animals.
Why?
Plants make LOTS of offspring (seeds).
Easier to have lots of growing plants in a lab.
Easier to control who breeds with who.

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Prior to the 1850’s, people believed in the idea of blending.
Blending is like mixing two paints together, you mix black and white, you get…
Gray!
But this didn’t make much sense…eventually everyone would look the same.

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With blending, if you crossed red with white, you’d always get pink.
Red X White
= Pink

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An Austrian monk,
Gregor Mendel, also thought this was quite odd and questioned the idea of blending.
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In the mid-1800s, in a series of experiments,
Gregor Mendel discovered the rules underlying patterns of inheritance.

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Question: Does blending occur?
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Prediction: No, blending does not occur.
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Test Hypothesis: Observed different characteristics in pea plants…some had wrinkled seeds and others had round seeds.
wrinkled round

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In your spiral…
Write a 3-4 sentence summary of what you learned about genetics yesterday.

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Planted one wrinkled seed and one round seed.
Transferred pollen from the wrinkled plant to the round plant, called cross-pollination.
If blending were occurring what would you expect to see as a result of this test?
Answer: slightly wrinkled seeds
Parent generation

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The resulting seeds were ALL round.
Therefore, proving Mendel correct that blending did not occur.

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This led Mendel to a second experiment, in which he planted two of the resulting round seeds in 2 other pots.
He cross pollinated the plants again.
This time, the results were different.
What do you think the results were?
First Generation

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This plant produced
3 round seeds and 1 wrinkled seed.
Mendel tested this many times and with different characteristics of the plants, and got the same pattern of results over and over.
Second Generation

Parent Generation
First Generation
Second Generation
Ratio = 3:1

(part 1)
Main Event (middle)
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Gregor Mendel’s
Experiments
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Include a description and drawing of the results of his experiments.
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Causes (left side)
Thinking back to what you learned yesterday, add the reasons that led to
Mendel’s experiments.
Why did he develop a hypothesis to test?

:
Statistics indicated a pattern.

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One trait was always present in the first generation, while the other trait seemed to disappear. Mendel called this trait the dominant trait.
Dominant Trait – the trait observed in the first generation when parents that have different traits
are bred. (Stronger trait)
Recessive Trait – the trait that seems to disappear in the first generation, but reappears in the second
generation. (weaker trait)
Mendel realized that his results could only be explained if each plant had two sets of instructions for each characteristic.

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First generation plants carried instructions for both the recessive and dominant trait.
Genes are the instructions for an inherited
trait. (wrinkled or round, we often use letters to represent each instruction)
Alleles are the different forms of a gene
(recessive or dominant) (R or r, use a capital letter to represent the dominant allele, and the same letter in lower case to represent the recessive allele)

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Phenotype is an organisms physical appearance or detectable characteristic.
(what you see) For example: round seeds, flower color, blue eyes, blonde hair, freckles etc.
What is the phenotype for the following pictures?

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Genotype is the combination of alleles that make up a specific trait.
(example: RR or Rr)
Homozygous is a genotype that has two of the same form of the allele.
(example: RR or rr)
Heterozygous is a genotype that has two different forms of the allele.
(example: Rr)

Genotype versus phenotype.
How does a genotype ratio differ from the phenotype ratio?

Female - mother
Male - father

A diagram that shows the occurrence of a genetic trait in several generations of a family.
Pedigree analysis reveals Mendel’s pattern in human inheritance

Hemophilia is a recessive trait defined by the absence of one or more of the proteins required for blood clotting.

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Probability is a mathematical chance that something will happen.
The probability of throwing heads or tails on a coin is 50%
(1/2 chances)

o
Helps predict the chance that something will happen o
Your predictions become more accurate with the more trials you run!

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Punnett square: a chart used to organize all of the possible combinations of offspring from particular parents.

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Look back and Mendel’s first experiment.
What allele should we use for the seed type?
The round seed is dominant over wrinkled, so use the letters R and r to represent the allele.
The genotype for the round seed is RR.
The genotype for the wrinkled seed is rr.

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RR x rr
R R r r