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.