Ch. 9 Fundamental Genetics • Gregor Mendel “Father of Genetics” • He is famous for his pea plant studies. • He taught high school math and was a monk. • Mendel studied pea plants with pure traits, in which the plant always produces offspring with that specific traits. • A pure trait is called a strain. • Ex. TT is a strain for a tall pea plant.
Mendel’s Experiments • 1. He studied the self-pollination strains of pea plants. He discovered 14 strains. (Picture) • A strain is called the P1(parental) Generation • 2. Mendel then used cross-pollination. • What is cross- pollination? • He crossed P1 Generation plants • These produced an F1(first filial) Generation • Ex. TT X tt plants Tall plants • Homozygous Tall X Homozygous Short 100% Tall
3. He then cross-pollinated the pea plants from the F1 Generation and collected the seeds. • The offspring produced from this generation was called the F2(second filial) Generation. • Ex. Heterozygous Tall X Heterozygous Tall ¾ Tall & ¼ Short. • There are two alleles per trait. • Ex. TT (both Ts are alleles)
Punnett Square • R=round peas(dominate) & r=wrinkled peas(recessive). • P1 Generation = strains (pure traits) • RR= round (dominate strain) • rr= wrinkled (recessive strain) • F1 Generation = Always heterozygous dominate. • F2 Generation = Always a 3 to 1 ratio.
Punnett Square F1 Generation All Heterozygous (Rr) r r R Rr Rr Rr Rr R R r F2 Generation 3:1 Ratio 3 tall : 1 short R RR Rr r Rr rr
Heredity • What is heredity? • The transmission of traits from parents to offspring. • The receiving of traits is called inheritance. • What is a gene? • A segment of DNA on a chromosome that controls a particular hereditary trait. • Ex. Blue eyes • Video - genetics
Traits • Traits have at least two alleles on them. • Lower case alleles are recessive. • Upper case alleles are dominate. • What are alike alleles called? • Homozygous: RR(dominate) & rr(recessive) • What are unlike alleles called? • Heterozygous • Three or more alleles are called multiple alleles.
Genotype is the type of genes an individual has. • It is the genetic make up of an organism • Ex. TT, Tt, or tt • Phenotype is the external appearance of an organism. • Ex. Tall or short
Probability is the likelihood for an event to occur. • # of a specific event / # of all events • 787 Tall plants / 1064 total plants = .739 • Codominace occurs when 3 or more alleles influence the phenotype. (Draw on the board). • Ex. R = red, R’ = white (P1 Generation) • Cross and get all RR’ (F1 Generation) • Cross and get RR, RR’, RR’, & R’R’ (F2 Generation) • RR = red, RR’ = pink, & R’R’ = white • Video – probability • Dihybrid Crosses