1. Introduction to Genetics
Chapter 11 Notes
Introduction to Genetics

2. Genetics – Study of heredity
Heredity – How things or characteristics (traits) are passed on from parent to offspring

3. Gregor Mendel ( )
1. “Father of Genetics” 2. Austrian Monk in the 1800’s – worked with pea plants 3. Why garden peas? - Reproduced by self-pollination - Have seven different traits (ex. Tall vs. short, round vs. wrinkled) 4. His experiments led to 4 Laws

4. Fundamental Laws of Heredity
Law of Unit Characters
Traits are controlled by factors called genes
For every trait you have 2 genes
1 from each parent
Law of Dominance
One of the gene pair can mask the other
The gene which appears or does the masking is called the dominant gene
The gene being masked is called recessive

5. Law of Independent Assortment
Law of Segregation
- During the formation of gametes (meiosis) each gamete only receives one gene from the pair. (The chromatids separate and go to separate cells)
Law of Independent Assortment
- Chance is involved in determining which gene a gamete will receive

6. Genetic Terms and Abbreviations:
Dominant Gene – (the masker) - Symbolized by a capital letter Recessive Gene – (the masked) - Symbolized by a small letter Homozygous – Alleles/genes are the same - Purebred  (TT, tt) Heterozygous – Alleles/genes are different - Hybrid  (Tt)

7. Genotype – The genetic make-up of an individual
-Letters (TT, Tt, tt)
Phenotype – The individuals physical appearance
- Words (tall, short, straight hair, green eyes, etc.)
Punnett Square – Resembles a checker board and shows the possible gene combinations of offspring

8. Abbreviations and Generations
P1 – Pure breeding parent generation F1 – (1st Fillial) Offspring generation; cross between members of the P generation F2 – (2nd Fillial) Offspring of crosses between members of F1 generation

9. Ratios for MONOHYBRID CROSSES
Phenotypic Ratio – Shows the ratio of physical traits How many dominant : How many recessive Ex. 3 Tall : 1 Short Genotypic Ratio – Shows the ratio of different genotypes Homozygous dominant: Heterozygous dominant: Homozygous recessive Ex. 1TT : 2Tt : 1tt

10. Example Monohybrid Cross
In humans, being a tongue roller (R) is dominant over non-roller (r). A man who is a non-roller marries a woman who is heterozygous for tongue rolling.
Father’s phenotype _____ Mother’s phenotype _____
Father’s genotype _____ Mother’s genotype _____
What is the probability of this couple having a child who is a tongue roller? ________

11. Example Monohybrid Cross
In humans, being a tongue roller (R) is dominant over non-roller (r). A man who is a non-roller marries a woman who is heterozygous for tongue rolling.
Father’s phenotype :non-roller Mother’s phenotype: roller
Father’s genotype : rr Mother’s genotype : Rr
R r r
What is the probability of this couple having a child who is a tongue roller? 2/4 = 50% Rr rr