Life Cycle - Plants (6B)
Pre Lab 

  • Exploring the history of genetics.
  • Investigating Mendel's research on plant genetics.
  • dominant
  • genetic
  • heredity
  • hybrid
  • recessive
  • Internet
  • overhead
  • worksheet

Students play the Mendal Pea game on the Internet.


Genetics is the study of heredity or the passing of traits from parents to offspring. Offspring can inherit dominant traits or recessive traits. A dominant trait is one that prevents another trait from appearing. A recessive trait is one that does not appear when a dominant trait is present. A pure trait (homozygous) is one that is made up of all dominant traits or all recessive traits. A hybrid trait (heterozygous) is a trait that is made up of a combination of dominant and recessive traits.

A gene is the unit of inheritance which is passed from parents to offspring. Genes occur in pairs in chromosomes inside the nucleus of a cell. There are dominant genes for dominant traits and recessive genes for recessive traits. Dominant genes mask recessive genes when paired. Gregor Mendel's experiments on hybridizing garden peas was the first recorded experiment on plant breeding. Mendel successfully studied the inheritance of unit characters. He also kept accurate records of how the characters reappeared in the offspring of selected parents. Mendel was also the first to control pollination techniques. These procedures are understood today, but in 1865 when Mendel's work was done, this was revolutionary. Mendel's work laid unnoticed for 35 years until European plant breeders rediscovered his work.

Mendel selected garden peas for his experiment. He took pollen from a dwarf growing pea and dusted it on a tall growing variety. The seeds resulting from this cross pollination were collected and planted the following season. All the plants that grew from these seeds were tall. Mendel reversed the situation and dusted the dwarf peas with pollen from the tall variety, and this resulted in offspring that were all tall.

Mendel then allowed the tall plants to self pollinate and found that 3/4 were tall plants and 1/4 were dwarf. From this result Mendel concluded that the expression of a given character was dominant, while the other character was recessive.

  1. Make an overhead of "Mendel's Garden Peas" to illustrate Mendel's result. It is important to go over this graph carefully with students because they will need to understand this for the lab. Capitol T is the dominant and small t is recessive. The dominant character will make the plants tall, while only two recessives together will form a dwarf.
  2. After students understand how to use the grid, go to the following web site and have the students breed their own hybrid pea with this interactive pea experiment.

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