1. 10/29/08
Lecture 22 – Genetics 1
− Gregor Mendel (Father of Genetics) – 1822-1884
− His famous paper was published in 1866.
− He performed test using the garden pea.
− There were many variation of the garden pea.
− It self pollinated.
− It was possible to cross.
− He developed true breeding lines
− He found alternate forms of a trait (monohybrid cross).
− Dihybrid crosses: 2 traits examined simultaneously.
− Monohybrid cross (example):
− We are examining flower color.
− Parents: Purple Flower X White Flower
− F1 generation: all plants have purple flowers
− F2 generation: F1 X F1
− Ratio: 3 purple flowers : 1 white flower
− The conclusions found are
− Each trait is controlled by a hereditary factor known a a gene.
− Diploid cells carry 2 copies of each gene.
− During gamete formation, the 2 forms are segregated (Mendel's Law of Segregation).
− On fertilization, the 2 gene condition is restored.
− Terms
− Gene: A unit of heredity that controls a trait.
− Allele: An alternate form of a gene.
− There is usually a dominant allele (represented by a capital letter) and a recessive allele (represented
by a lower case letter).
− Dominant: The form that persist in the F1 generation.
− Recessive: The form that does not appear in the F1 generation but in the F2 generation.
− Homozygous: When the two alleles are the same.
− They could be homozygous dominant or homozygous recessive.
− Heterozygous: When the two alleles are different.
− Phenotype: Observable or measurable part of the genetic make-up.
− Genotype: The actual genetic make-up of the organism.
− Locus: The location of a gene on a chromosome.