Gregor Mendel and Genetics
Biology 3 09-10Kent Kawashima
Spermists
• Dutch microscopist Anton van Leeuwenhoek (1632-1723) discovered "animalcules" in the sperm of humans.
• Some scientists speculated they saw a "little man" or homunculus inside each sperm.
• Female contribution was the womb in which the homunculus grew, and prenatal influences of the womb.
Ovists
• Believed that the future human was in the egg, and that sperm merely stimulated the growth of the egg.
• Women carried eggs containing boy and girl children, and that the gender of the offspring was determined well before conception.
Pangenesis
• Pangenesis was an idea that males and females formed "pangenes" in every organ.
• Pangenes moved through the blood to the genitals and then to the children.
• The terms "blood relative", "full-blooded", and "royal blood" are relicts of pangenesis.
Blending Theory
• The mixture of sperm and egg resulted in progeny that were a "blend" of two parents' characteristics.
• According to the blenders, when a black furred animal mates with white furred animal, you would expect all resulting progeny would be gray since it is a color intermediate between black and white.
Law of Segregation
• There are two alleles for every gene determining a specific characteristic
• Alleles are segregated into separate gametes during reproduction.
Mendel's work showed
• Each parent contributes one factor of each trait shown in offspring.
• The two members of each pair of factors segregate from each other during gamete formation.
• The blending theory of inheritance was discounted.
• Males and females contribute equally to the traits in their offspring.
• Acquired traits are not inherited.
Dihybrid Cross
• Smooth seeds (S) are dominant over wrinkled (s) seeds.
• Yellow seed color (Y) is dominant over green (g).
Law of Independent Assortment
• Mendel’s Law of Independent Assortment says that 2 or more different genes, if found on separate chromosomes, are determined independently of each other.