Is the scientific study of heredity Heredity: characteristic that can be passed from parent to offspring –Ex: Height, eye color… Founding father: Gregor Mendel Austrian monk Worked with pea plants

Important terms Traits – characteristics that are inherited Gametes – male and female sex cells Fertilization – male gamete unites with female gamete Zygote – the fertilized cell Pollination – transfer of pollen to ovary in flowers Hybrid – offspring of parents with different forms of a trait

Mendel’s Experiments Used the Garden Pea for Three reasons: –1) Structure of the flowers –2) The distinct traits –3) quick reproduction cycle

Mendel’s Observations Self pollinated the plants (pure breds) to make a P generation. The offspring from the P generation = F1 generation (F stands for filial = offspring) Allowed F1 to self fertilize and their offspring is the F2 generation

Mendel’s Observations Noticed that all F1 generations were of one trait; he called that trait dominant. Dominant would always appear in the F1 generation Recessive would appear in the F2 generation (3:1)

Mendel’s Conclusions Proved the Blending Theory wrong Hypothesized about “factors” controlling traits

Mendel’s Conclusions Mendel’s factors are genes = sections of chromosome that code for a trait. –Allele = distinct or different form of a gene –Could be two forms for one trait: Dominant or Recessive alleles. –Dominant is the expressed allele –Recessive is not expressed when a dominant is present

DOMINANT ALWAYS WRITTEN IN CAPITAL LETTER (Y) recessive always written in lower case (y)

Genetic make up = GENOTYPE –Includes both genes in a homologous pair of chromosomes

Genetic make up = GENTOTYPE –Includes both genes in a homologous pair of chromosomes –Pure breds= YY or yy –Hybrids = Yy –Homozygous = two alleles are identical (RR) –Heterozygous = two alleles are different (Rr)

Phenotype = outward expression of trait PHYSICAL APPEARANCEPhenotype = PHYSICAL APPEARANCE

Principles of Inheritance Chromosome Theory of Heredity: material of inheritance is carried by the genes in chromosomes.

REVIEW What result would you predict for Mendel's cross of a short pea plant with a tall one in the P generation?

REVIEW Define: genotype, phenotype, homozygous, heterozygous, dominant, recessive, allele, purebred, hybrid, trait, homologous pair. Explain the Chromosome Theory of Inheritance What is the Blending Theory, how did Mendel disprove it?