Introduction to Genetics Chapter 11 Notes Introduction to Genetics

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

Gregor Mendel ( 1822-1884 ) 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

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

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

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)

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

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

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

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? ________

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