Mendel’s Three Genetic Laws

We spoke in class about Mendel’s Three Laws of Genetics —it is so imperative that each of you learn them. We will do more review in class—-

I. The Law of Dominance

If a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.

My explanation: Cross PP x pp and all offspring with be Heterozygous Pp and all purple.

—–Any time two parent organisms look different for a trait, and all their offspring resemble only one of the parents, you are dealing with Mendel’s Law of Dominance

2. The law of Segregation—During the formation of gametes (eggs and sperms), the two alleles responsible for a trait separate from each other. Alleles for a trait are then”recombined” at fertilization, producing the genotype for the traits of the offspring.

My understanding: Mendel crossed plants from the F1 generation, Pp and Pp,  3/4 plants will be purple and 1/4 will be white. —-Therefore, the genes must segregate themselves between the production of sex cells and fertilization. —This must happen in the process of Meiosis, which is the production of sex cells, egg and sperm.

Any time two parents have the same phenotype for a trait (tall, short, purple, white, etc) but some of their offspring look different with the respect to that trait, the parents must be hybrid or heterozygous for a trait.

3. The Law of Independent Assortment—Alleles for different traits are distributed to sex cells and offspring independently of each other.

Mendel realized that height, shape, color, texture, or any of the peas plant traits had an impact on each other. So, being tall wouldn’t determine if the plants would be green or yellow. Therefore, different traits seemed to be inherited INDEPENDENTLY.  Example: RrGg x RrGg, round green x round green will produce 9/16 round green, 3/16 round yellow, 3/16 wrinkled green, 1/16 wrinkled yellow