Mendel and his Pea Plants (pgs. 18-20)

When 2 distinct individuals with different characteristics are mated or crossed, this is called a hybridization. The offspring are referred to as hybrids (18).
In plants, fertilization occurs when sperm enters the micropyle in the ovule wall and fuses with an egg cell (20).
Gamete is used to describe the haploid reproductive cells that can unite to form a zygote (20).
The process of crossing the genetics of 2 plants rather than allowing them to self-fertilize is called cross-fertilization. This requires that the pollen from one plant be placed on the sigma of another plant (20).

7 Traits that Bred True (pgs. 20-21)

Unique characteristics of an organism are called traits (20).
"Bred true" means that a trait did not vary in appearance from generation to generation. A variety that continues to produce the same characteristic after several generations of self-fertilization is called a true-breeding line, or strain (20).
A variant refers to a particular trait that may be found in 2 or more variations within a single species (20).
A cross in which an experimenter is observing only 1 trait is called a single-factor cross, or a monohybrid cross (20).
- When the parents are different variants for a given trait, this type of cross produces single-trait hybrids, also known as monohybrids.

Following the Outcome of a Single Trait for 2 Generations (21-23)

Mendel began with true-breeding plants that differed with regard to a single trait. This is the parental, or P, generation (21).
The true-breeding parents were crossed with each other (P cross) and the offspring was called the F1 generation. All of these plants showed the phenotype of one parent, but not the other (21).
The F1 generation was allowed to self-fertilize, and this made the F2 generation (21).
Mendel proposed 3 different ideas:
1. The variant for 1 trait is dominant over another variant. Recessive is used to describe the variant that is masked by the presence of a dominant trait.
2. When a true-breeding parent with a dominant trait was crossed with a true-breeding recessive parent, the dominant trait is was always observed in F1, but was variable in F2. Because he observed recessive traits only in the 2nd generation, he proposed that the genetic determinants of traits are passed along as "unit factors", which are now called genes. This was consistent with the particulate theory of inheritance (22-23).
3. There is always a 3:1 ratio between the dominant and recessive in the F2 generation (23).

	Created by Olivia McRitchie over 6 years ago

NCLEX Biology (Genetics) Note on Chapter 2- Mendelian Genetics, created by Olivia McRitchie on 26/03/2018.