1. Introduction to Mendelian Genetics
Inheritance of Traits
Introduction to Mendelian Genetics

2. Golden Doodle Blending Theory - offspring are a straight mix.
A Brief History
In the past, people did not understand how traits were inherited, but there were many guesses based on things that could be observed.
Two theories emerged….
Blending Theory - offspring are a straight mix.
Particulate Theory - traits are inherited as "particles", offspring receive a "piece" from each parent, some pieces may hide the others.
Golden Doodle

3. Who was Gregor Mendel? GENETICS – study of heredity
He was known as the “FATHER OF GENETICS”
He discovered how traits were inherited.
GENETICS – study of heredity
HEREDITY – the passing of traits from parents to offspring

4. Mendel’s Peas Mendel did his study on pea plants
which are easy to cross and have many traits.
tall/short
purple /white flowers
smooth/wrinkled seed

5. Pea plants can easily be self-fertilized or cross-fertilized

6. True-Breeding Plants -always create plants that look like themselves (purple or white flowers)
Hybrids – offspring of two different true breeding plants (Purple x White = Hybrid)

7. Principle of Dominance & Recessiveness
Some traits are dominant over others.
- Tall parent x Short parent = all tall hybrids
*Tall, purple, and smooth are dominant traits (always observed if present)
* Short, white, and wrinkled are recessive traits (hidden in presence of a dominant trait)

8. Mendel discovered that each trait is controlled by variations of genes (allele)
Genes – segment of DNA that determine your traits
Genes are located on chromosomes

9. Homologous Chromosomes & Alleles
Organisms have sets of chromosomes with each chromosome having a unique set of genes. Many organisms have two copies of each chromosome, one from each parent.
Chromosomes that have the same genes are called homologous chromosomes because they have the same genes (homo=same, logos – relation).
They may have the same genes, but can have different versions of those genes, called alleles.

10. Principle of Segregation
When a parent makes sperm or eggs, their homologous chromosomes separate so that each sperm or egg cell has only one of the two possible alleles.
The gametes (egg or sperm) contain only one of the two possible chromosomes.
Question: Why is it necessary to donate only one copy of each chromosome to the child when humans normally have 2 copies?

11. 1. The “Father of Genetics” is ____________
Quick Check - What do we know so far?
1. The “Father of Genetics” is ____________
2. Genetics is the study of _____________, which is how traits are passed from _________ to ____________
3. Mendel studied what organism? ____________
4. If one trait covers up another one, we say that it is ______________, the one that is covered up is ______
5. A “true-breeding” plant is one that can only produce plants like itself a) true b) false
6. If a tall and a short plant are crossed, it will create a
a) zygote b) gene c) hybrid

12. Mendel’s Experiments

13. Mendel’s Crosses Explained
T is the allele for tall (dominant)
T is the allele for short (recessive)
Y is the allele for smooth (dominant)
y is the allele for wrinkled (recessive)

14. GENOTYPE  -  the pair of alleles an organism has for a gene (TT, Tt, tt)
PHENOTYPE   - the observable trait determined by the genotype

15. 2. Who was the father of genetics? _________
Check for understanding
1.   The passing of traits from parents to offspring is known as  ____________________
2.  Who was the father of genetics?  _________
3.  Genes are located on _______________
4.  Every gene is made of two
a. genotypes b. alleles c. cells
5. The organism’s outward appearance, such as wrinkled seeds are referred to as the a) phenotype b) genotype

16. 6. The letters (ex. RR) that represent the traits are referred to as the a) phenotype b) genotype
7. An organism that has two different alleles, or letters, such as Rr is: a) homozygous b) heterozygous
8. 7. An organism that has two of the same alleles, or letters, such as RR is: a) homozygous b) heterozygous
9. Which of the following sets would represent Mendel’s Parent (P) generation?
a) RR x RR b) Rr x Rr c) RR x rr
10. When two different alleles occur together, such as Rr, the one that is expressed is a) dominant b) recessive

17. What does this letter actually represent?
11. What is the diagram shown below called?
What does this letter actually represent?

18. Check for understanding
1.  A one-eyed purple people eater is crossed with a two eyed purple people eater.  All of their offspring have two eyes.   Which trait is dominant?

19. 2. If you use the letter E for this gene
2.  If you use the letter E for this gene.   What is the genotype of the offspring if the parents were EE x ee
    
3.  If you crossed the offspring with each other?  How many of the new offspring would you expect to have two eyes?
EE = two eyes
Ee = two eyes
ee = one eye

20. Video Review: Extra Credit
Link if video isn’t working: