1. Heredity

2. Your Physical Appearance
Heredity is the passing of traits from parents to an offspring.
Gregor Mendel was the first scientist to successfully study inheritance
He is the “Father of Genetics”

3. Why Pea Plants? Mendel use Garden Pea Plants for his research because:
They grow quickly
They naturally self-pollinate

4. Mendel’s Success
Mendel was successful with his pea plant research because:
he studied one trait at a time! (independent variable)
He had studied statistics
*A trait is a distinct phenotypic characteristic that may be inherited

5. Pea Plant Traits Flower Color Flower Position Seed Color Seed Shape
Pod Shape
Pod Color
Plant Height

6. The Experiment
Mendel began by taking pure trait plants and cross-pollinating them
He did this by hand, not with bees!

7. The Experiment Part I (Example 1)
Plant height
Mendel crossed a Tall parent plant with a short parent plant:
Tall x short = All Tall
TT x tt = Tt
parent x parent = First Filial (F1)
Both parent plants were true-breeding: They always produced the same type of offspring.

8. The Experiment Part I (Example 2)
Flower Color
Mendel crossed a Purple parent plant with a white parent plant:
Purple x white = All Purple
PP x pp = Pp
parent x parent = First Filial (F1)

9. The Experiment Part II
He wondered why one trait disappeared when he crossed the two pure (true-breeding) plants
He decided to allow the new F1 plants to naturally self-pollinate and here is what he found……..

10. Example 1- Plant Height F1 Tall plants self-pollinate and produce:
25% short plants

11. Example 2 - Flower Color F1 Purple Flower color plants
self-pollinate and produce:
75% Purple flowers
25% white flowers

12. Mendel’s Conclusion
The Principle of Dominance and Recessiveness states that one trait is more likely to occur than the other.
Dominant is a trait that is most likely to occur
Recessive is a trait that is usually hidden in the first generation, but may reappear later

13. Probability
The chance or possibility that a certain outcome will occur. Usually written as:
Fractions
Decimals

14. Let’s Learn a New Language..
Genotype- the genetic make-up of an organism (TT, Tt, tt)
Phenotype- the physical appearance of an organim (Tall, short, Purple, white)
Dominant- more likely to occur (The tall plants or the purple flowers)
Recessive- less likely to occur (The short plants or the white flowers)

15. Let’s Learn a New Language..
Homozygous- when both alleles are the SAME
Homozygous Dominant: TT, PP, WW
Homozygous Recessive: tt, pp, ww
Heterozygous- when each allele is DIFFERENT
Tt, Pp, Ww

16. Let’s Learn a New Language..
An Allele is an alternate form of a gene; one part of a pair
A Gene is composed of two alleles, one from each parent
Allele Allele = Gene
T(mom) t(dad) = Tt(child)

18. Punnett Squares
Developed by Rudolph Punnett to make genetics easier for us to understand

19. Genetics Example 1
In garden pea plants, tall plants are dominant (T) and short plants are recessive (t). A pea plant that is homozygous dominant for height is crossed with one that is homozygous recessive for plant height.
Draw a Punnett square to represent the problem.
What are the possible genotypes?
What are the possible phenotypes?
What is the probability of each genotype?
What is the probability of each phenotype?

20. Genotypes
Phenotypes
Probability of genotypes
Probability of phenotypes

21. Genetics Example 2
In garden pea plants, purple flower color (P) is dominant over white flower color (p). A pea plant that is homozygous recesive for flower color is crossed with one that is heterozygous for flower color.
Draw a Punnett square to represent the problem.
What are the possible genotypes?
What are the possible phenotypes?
What is the probability of each genotype?
What is the probability of each phenotype?

22. Genotypes
Phenotypes
Probability of genotypes
Probability of phenotypes

23. Genetics Examples
In garden pea plants, yellow seeds (Y) are dominant and green seeds (y) are recessive. What offspring would result if two heterozygous plants were crossed?
Draw a Punnett square to represent the problem.
What are the possible genotypes?
What are the possible phenotypes?
What is the probability of each genotype?
What is the probability of each phenotype?

24. Genotypes
Phenotypes
Probability of genotypes
Probability of phenotypes

25. More Genetics

26. Incomplete Dominance
Sometimes one trait is not completely dominant over the other
The same letter allele is used
Red x White = Pink
RR x R’R’ = RR’
This results with a combined genotype
Snap dragons

27. Codominance Sometimes both traits are equally dominant
Different letter alleles are used
Black x White = Checkered
BB x WW = BW
This results in both traits being expressed
Checkered Chickens

28. Alternate forms of Genetics
Gregor Mendel studied simple genetic inheritance:
Offspring were either dominant or recessive
But not all traits are simple!!

29. Thomas Hunt Morgan Studied Fruit Flies Discovered Gender inheritance
Other traits associated with gender

30. Gender
Gender is always determined by the male

31. Sex-linked Traits Some traits are only located on the “X” chromosome
Since Males only have one “x” chromosome, they are more likely to show the trait than a female with two “x” chromosomes

32. Sex-linked Traits
Colorblindness
Hemophilia
Muscular dystrophy

33. Colorblindness Charts

34. Other Types of Inheritance
Name:
Description:
Examples:
Multiple
Allele Traits
Traits can be determined by 3 or more alleles
Fur Color in Rabbits, Blood Type in Humans
Polygenetic
Traits
Traits are determined by more than one GENE
Human height, Human eye color
**Most Traits that can have a “range”