1. Introduction to Genetics
Chapter 9
Introduction to Genetics

2. List as many traits as you can that could be inherited

3. Who was Gregor Mendel? 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
Trait – a genetically determined characteristic

4. Mendel’s Peas Mendel did his study on pea plants
Pea plants have many traits (tall/short, purple flowers/white flowers)
Pea plants can
be self-fertilized or
cross-fertilized

5. Purple True-Breed x White True-Breed = Hybrid
Types of Plants
True-Breeding - these plants always create plants that look like themselves
Hybrids – offspring of true-breeding plants
Purple True-Breed x White True-Breed = Hybrid

6. Dominance Some factors are dominant over others.
Purple true-breed x White true-breed = all purple offspring (hybrids)
- Therefore, purple is the dominant factor
- White is the recessive factor

7. Types of Inheritance (dominance)
Complete - the dominant allele's trait masks the recessive allele's trait
Incomplete - the trait seen is a blend of the two allele's traits
Codominant - both alleles' traits are fully expressed

8. Genes and Alleles
Genes – a short segment of DNA that contains the instructions for a single trait
- remember at the time Mendel was experimenting DNA was unheard of so he knew genes as factors that determine a trait
Mendel discovered that each trait is controlled by two factors (alleles)
- allele: is an alternative form of a gene.
- ex. purple vs white flower color

9. Mendel’s Experiments
Draw the crosses
(it will take up all this space)

10. Mendel’s Experiments
The 'F' stands for filial, which in Latin means “of a son or daughter”
Draw the crosses

11. Mendel’s Experiments
Draw the crosses

12. Mendel’s Experiments
Draw the crosses

14. Explaining the Crosses
Principle of segregation - When a parent makes sperm or eggs, their genes separate
The gametes (egg or sperm) contain either a P allele (purple) or a p allele (white) P p

15. Recall: Law of Independent Assortment
Chromosomes separate independently of one another during the formation of gametes

16. Below is an example of a complete dominance trait: height
Vocab
Genotype - what gene alleles (letters), the organism has
- ex. TT, Tt, tt
Phenotype - what it looks like
- ex. tall or short
Below is an example of a complete dominance trait: height
Genotype
Phenotype TT
tall Tt tt
short

17. Describing Genotypes Homozygous: two types Homozygous dominant: TT
Homozygous recessive: tt
Heterozygous: Tt

19. Let's review what you know about genetics......

20. Types of Crosses
Testcross – an individual with unknown genotype crossed with a homozygous recessive individual
Why did I put one dominant allele for the individual of the unknown genotype? t T Tt ? ?t

21. Polygenic Traits a compound word poly meaning many
genic refering to genes
Polygenic - a trait that is controlled by more than one gene
Medel was lucky and studied traits that were not polygenic. Polygenic traits (human eye color) are much more complicated than single gene traits (pea flower color)

22. 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?
2.  If you use the letter T for this gene.   What is the genotype of the offspring? 
3.  Are these offspring the F1 or F2
generation?
4.  If you crossed the offspring with each other?  How many of the new offspring would you expect to have two eyes?

23. 5.   The passing of traits from parents to offspring is known as  ___________________________
6.  Who was the father of genetics?  __________
7.  A single gene will code for a _______________, such as flower color.
8.  Every gene is made of two ______________