CHAPTER 11 NOTES – Mendel and His Discoveries
Inheritance is viewed as a “black box”
Genetics – the study of inheritance
Study began with Gregor Mendel (Austrian Monk and naturalist)
Had no knowledge of chromosomes, meiosis or DNA
Used scientific method
Experimental Organism – Pisum sativum (common garden pea)
Performed in present-day Czech Republic
Genes – elements of NA located on chromosomes
Make up 2% of DNA
BASES
A – Adenine
T – Thymine
C – Cytosine
G – Guanine
Cycle of a Pea Plane
1. Self-pollination
2. Fertilization
3. Germination
4. Development
For each character of the plant, there are two traits
Dominant represented by CAPITAL letters
Recessive represented by lower case letters
Genotype – genetic makeup of an individual
Phenotype – features and characteristics of an individual
Determined by its genotype under some conditions and its environment under others
Yellow seeds were dominant (Y)
Green seeds were recessive (y)
Parental generation “P generation”
Offspring of P “F1 generation” (first filial generation)
Offspring of F1 “F2 generation” (second filial generation)
What did Mendel learn?
No “blending” of characteristics
Heredity is due to the transmission of discrete elements
Green seeds were absent from F1
Green seeds reappeared in F2
F1 individuals retained a green-seed element
Traits are caused by PAIRS of elements
F1 individuals must possess a yellow-seed element
F1 individuals also possess a green-seed element
Pairs of elements represent genes
