A scientist and monk, Gregor Mendel, in the 1800s was the first to actually count numbers of offspring in crosses.
father of genetics.
true-breeding varieties Fig 11.3
P or parental generation
F1 generation or first filial generation.
Used seven pairs of contrasting traits. Table 11.1
to recessive phenotype in the F2
When F2 plants were allowed to self-fertilize, Mendel found a 1:2:1 ratio of true-breeding dominant to not true-breeding dominant to true-breeding recessive.
Today we use these terms:
Each individual has two factors (we now call these genes) for each character. These are located on homologous chromosomes. Fig 11.6
character - a heritable feature.
trait - a variant for a character.
Punnett Squares Fig. 11.7
How Mendel analyzed
flower color Fig
The Testcross - When Mendel did not know the genotype of an individual expressing a dominant trait, he did a test cross by crossing the individual with a homozygous recessive for the character. Fig 11.9
Mendel's First Law: Law of
Mendel's Second Law: Law of Independent Assortment was determined when he worked with two traits at a time in dihybrid crosses. Fig 11.10 Crossing two individuals that are heterozygous for both characters yields a phenotypic ratio of 9:3:3:1. If the genes are located on the same chromosome, they would be linked. image
Exceptions to Mendel's Laws
- (polygenic) Fig. 11.12. Human skin color image
and eye color. Eye color.
Pleiotropic Effects - Ex: cystic fibrosis. Fig 11.13
Incomplete Dominance - Fig 11.14.
Environmental Effects - Fig 11.15
Epistasis. Fig 11.16 Fig 11.17 and image
Codominance - Fig 11.18
Multiple Alleles with codominance