Lecture 2 Flashcards
What is Darwin’s blending theory?
Offspring inherits traits as a blend, like mixing paint colors. Inherited traits become mixed and average out over generations.
What is Mendel’s theory?
Traits are inherited as discrete genes and units. They are not blended.
What is Mendel’s 1st Law?
The Law of Segregation:
1- Two elements of heredity for each trait in each individual.
2- These two elements separate or segregate during reproduction.
3-Offspring receive one of the two elements from each parent.
4-Mendel’s first law ended the discussions for blending theory.
What is Mendel’s second Law?
The Law of Independence:
The inheritance pattern of one trait will not affect the inheritance pattern of another.
For example, A cat with a short tail can be either brown or white independently.
Single Gene Mutation ( Huntington’s Disease)
1- Brain disorder causing progressive deterioration of brain cells that leads to severe incapacitation and eventual death.
2-Symptoms: uncontrollable movement, abnormal walking balance, slurred speech, thinking difficulties, and personality changes.
3- There is no cure and no effective treatment.
Single Gene Mutation (Phenylketonuria)
1-Metabolic disorder that prevents normal metabolisation of phenylalanine, which is present in protein-rich food.
2-Damage occurs to nervous system leading to mental retardation.
3- Prevention is done by a diet.
Scurvy
1- A disorder caused by a single gene in humans. However we don’t consider it a genetic disorder in humans.
2- Humans don’t produce vitamin C; everyone has that defective gene.
3- It can be prevented by consuming vitamin C.
Exceptions to Mendel’s law of Independence?
1- The law doesn’t hold for genes in close proximity on the same chromosome.
2- If any two traits have genes in close proximity then the traits won’t be passed independently.
What is a trait that famously passes down together with other traits?
SEX. Sex passes down colorblindness and hemophilia for males.
