Chapter 10, Lesson 1 Notes
What Did Mendel Discover?
Mendel studied the inheritance of genetic traits by working with
garden pea plants. He studied 7 traits--plant height, flower
position, flower color, seed color, seed shape, pod color, and pod
shape. He discovered two laws—the law of segregation and the
law of independent assortment based on two generations of pea
plants (F1 Generation and F2 Generation).
The F1 Generation
The F1 generation is the first generation of offspring from the
cross of 2 parents (the P generation) with just one different
trait (e.g., plant height).
The F1 generation were hybrids (the offspring of two
different true-breeding plants)
The F1 offspring always showed the dominant trait of the
parents because a dominant trait will always hide a recessive
trait.
Example: All F1 generation plants were tall because tall is a
dominant trait over short.
The F2 Generation
The F2 generation is the offspring of two of the hybrid plants
from the F1 generation.
The trait that had disappeared (recessive gene) in the F1
Generation now appeared in the F2 Generation (short plant).
Example: One out of four F2 Generation plants was short, 3
were tall.
The Law of Segregation
This law states that an organism gets two genes for each trait.
One gene comes from each parent.
Genes that come together with the same alleles (forms of the
same gene) are homozygous, resulting in the same trait in
offspring.
Genes that come together with different alleles are
heterozygous. The dominant allele is displayed in a
heterozygous pair.
The Law of Independent Assortment
This law states that each pair of chromosomes separate into
four possible pairings of genes in an F2 generation.
(Draw Figure 10.1.1 on p. 280 to demonstrate F1 and F2
generations)
Punnett Squares
Punnett Squares are models that help explain the results of
Mendel’s cross pairings.
(Draw Figure 10.1.2 on p. 281 to demonstrate a Punnett Square for
an F1 generation)
(Draw Figure 10.1.3 on p. 282 to demonstrate a Punnett Square for
an F2 generation).
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