Genetics and Inheritance

Genetics is the study of heredity. Johann Gregor Mendel created the framework for how to study genetics long before chromosomes or genes had been identified.

Through his work, Mendel was able to reveal the fundamental principles of heredity. His work and theories are referred to as “classical” or Mendelian genetics. We now know that genes carried on chromosomes are the basic functional unit of heredity.

We also now know that not all genes are transmitted from parents to offspring according to Mendelian genetics, but Mendel’s experiments served as an excellent starting point.

Mendel’s Crosses Mendel worked with the garden pea species, Pisum sativum, to study inheritance. Pea flowers have both male and female parts. Normally, pollen from the male part of the pea flower fertilizes the female egg cells of the very same flower.

Because the pollen produced by the plant fertilizes the egg cells of that very same plat, peas are said to produce seeds by self- pollination. Seeds produced by self pollination inherit all of their characteristics from the single plant that bore them.

Mendel learned that self- pollination could be prevented. He carefully cut the male parts off all the flowers of one plants and did the reverse for another plant. He then pollinated the two plants by dusting the pollen from one plant onto the flower of the other plant. This is known as cross- pollination. Cross-pollination produces seeds that tare the offspring of two different plants.

Using this technique, Mendel was able to cross plants with different characteristics. Mendel then obtained seeds from these crosses that he then grew into plants. There plants were hybrids, or organisms produced by crossing parents with different characteristics.

Dominant traits: Recessive traits: Those that are inherited unchanged in a hybridization   Recessive traits: Those that become latent, or disappear in the offspring of a hybridization. Can reappear in the progeny of the hybrid offspring.