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Principles of Genetics Cheat Sheet (DRAFT) by

Principles of Genetics and Mendalian Genetics

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Mendalian Genetic

Gregor Medal - Father of Modern Genetics
Why Pea?
Austrian monk who studied heredity in pea plants.
easy to grow and redily available
Developed laws of inheri­tence.
control fertil­izaton and reproduce rapidly
Conducted experi­ments on Pisum sativu­m(pea plants)
easily distin­gui­shable, distinct trait

Laws of Inheri­tence

Law of Dominance
Law of Indepe­ndent Assortment
Law of Segreg­ation
Hybrid offspring will only inherit the dominant trait in the phenotype. The alleles that are suppressed are called the recessive traits while the alleles that determine the trait are known as the dominant traits.
A pair of traits segregates indepe­ndently of another pair during gamete formation. As the individual heredity factors assort indepe­nde­ntly, different traits get equal opport­unity to occur together.
During the production of gametes, two copies of each hereditary factor segregate so that offspring acquire one factor from each parent. In other words, allele (alter­native form of the gene) pairs segregate during the formation of gamete and re-unite randomly during fertil­iza­tion.
 

Non-Me­ndalian Inheri­tence

Co-Dom­inance
Incomplete Dominance
Polygenic Inheri­tance
Multiple alleles
Pleiotropy
Where both the alleles are expressed equally.
The traits blend together producing an interm­ediate phenotype. If two flowers are crossed together, a hybrid will be produced that is in between both the parents.
Where one trait is controlled by several genes.
Mendel studied only two alleles in pea genes but real population often have mutiple alleles for a given gene.
When one gene affects multiple charac­ter­istics and not just a single charac­ter­istic
e.g: The AB blood group where both the allelles Ia and Ib are dominant and expressed equally.
e.g: in snapdragon plant, if a homozygous white flower is crossed with a homozygous red flower, a pink flower is obtained.
e.g: skin color, eye color, height
e.g: The ABO blood type in humans are controled by three different alleles, IA, IB, i
e.g: Marfan Syndrome results in several symptoms such as very tall height, thin fingers, heart problems, disloc­ation of lens, etc. These symptoms are not related directly, but are caused by the mutation of a single gene.