4 Mendel’s Work Gregor Mendel- b.1822- Father of Genetics Studied 7 different traits: seed shape & color, seed coat color, pod shape & color, flower position and plant height.Pollination- transfer of pollen (carries sperm) to female part of flower (pistil)Self- pollen to same plant= 1 parentCross- pollen to different plant= 2 parents
6 Mendel’s WorkMendel cross pollinated pure breeding pea plants with opposing alleles.EX: P (parent) generation= tall (TT) & short (tt)F1 cross= tall (TT) X short(tt)F1 (first filial) Generation = all tall (Tt)F2 cross= tall (Tt) X tall (Tt)F2 Generation = ¾ tall (TT or Tt) ¼ short (tt)
8 Mendel’s Work From his results he concluded that: If an allele is expressed (shows up) in a hybrid, then the allele is dominant(T).If an allele is NOT expressed in a hybrid, then the allele is recessive(t).Phenotype- traits that show up in the organism.Genotype- genetic makeup (allele combination) of the organismHomozygous (pure)- both alleles the same EX: TT or ttHeterozygous (hybrid)- alleles differ EX: Tt
9 Mendel’s Principles: Mendel’s Work Genes determine biological characteristics.Offspring receive one allele for a gene from each parent.One allele may be dominant over another.Some genes segregate independently.
11 ProbabilitiesThe likelihood that one trait or another will show up in offspring.EX: ¼ BB, ½ Bb, ¼ bb25% BB, 50% Bb, 25% bb1 in 4 BB, 1 in 2 Bb, 1 in 4 bb1:2:1
12 Incomplete DominanceOccurs when the alleles for a gene are neither dominant nor recessive.Heterozygous organisms display a blend of both traits.EX: Snapdragons flower color- RR= red rr= white Rr= pink
16 Multiple Alleles Occurs when a gene has more than two alleles. Produces a variety of different phenotypes.EX: Blood type in humans- three alleles= A, B, & O.Type A= AA or AOType B= BB or BOType O= OOType AB= ABNote: both A and B alleles are dominant over O.