Introduction to Genetics Chapter 11 Introduction to Genetics

Genetics = study of heredity Gregor Mendel – Austrian monk, mid-late 1800s “Father of Genetics” Studied pea plants

Good b/c: *** Self-pollinate * Grow quickly * Many offspring *** Show 1 of 2 possible outcomes for traits * Easy to grow * Short life span

Mendel’s Experiments Step 1 – Let plants self-pollinate, so they produce identical offspring => pure-bred plants = Parental Generation (P) Ex. Tall plants produce tall offspring

Step 2 – took 2 different types of P generation plants & crossed them (mated) - offspring = First filial generation (F1) Ex. Tall X short -> all tall offspring

Step 3 – allowed F1 gen. to self-pollinate - offspring = Second filial generation (F2) - offspring was mostly tall, some short - Calculated totals -> average ratio 3:1 in F2

Mendel’s Conclusions Parents transmit info = “factors” (now genes) Everyone has 2 factors (1 from mom, 1 from dad) Factors – homozygous – same type of factor heterozygous – different form of factor

3) Alternate form of a factor = allele ex. If tall, allele = T; if short, allele = t Genotype = genetic makeup Ex. Tt Phenotype = physical appearance Ex. tall

4) Alleles segregate randomly during meiosis 5) Dominant alleles = control, seen recessive alleles = hidden

Mendel’s Laws LAW OF SEGREGATION = each pair of alleles segregates during gamete formation (meiosis) LAW OF INDEPENDENT ASSORTMENT = gene pairs segregate into gametes randomly and independently of each other

LAW OF DOMINANCE = One allele is shown, one is hidden