Genetics Chapter 3 Flashcards
Mendels Law of Segregation
every individual possesses two alleles and only one allele is passed on to the offspring
Codominance
When both alleles are fully expressed
Polygenetic
Traits Controlled by more than one gene
Pleiotrophy
One gene affecting multiple traits
Ex. Sickle cell anemia affecting red shaped blood cells and anemia
Epistasis
when one gene controls the expression of another
Polymorphic
More than just two possible alleles in the population
Penetrance
Some genes are not expressed and only expressed at a certain level
Incomplete Dominance
Blend
Codominant
Both phenotypes apparent
Bombay Allele
law of independant assortment
inheritance of one trait does not affect the inheritance of a second traits.
Example. inheriting a particular allele for eye color does not affect the ability to inherit any other allele for hair color
law of dominance
receive alleles are often broken
Gene
a section of DNA responsible for a trait.
ex. gene responsible for eye color
Allele
variant form of gene
ex. gene for eye color can have alleled for brown eyes or blue eyes.
Chromosomes
contains many genes (X shape)
Cystic Fibrosis, sickle cell anemia , hemophilia A
Due to the allele encoding a defective protein(loss-of-function-allele) or that isn’t express at all (null allele)
homologous
Simillar chromosome , different alleles
think back: homologous to analogous –> similar ancestor same parts diff functions vs. similar functions but no common ancestor
reciprocal recessive epistasis
2 genes need to be expressed for the trait to be expressed.
both genes must have at least one dominant allele for the trait to be expressed.
f2 ratio 9:7 (dom to recessive)
Achondeoplasia
a genetic disorder affecting bone growth leads to a common form of dwarfism.
heterozygote advantage
ex. genetic diseases are caused by recessive alleles. Usually removed from population through natural selection.
except for, SICKLE CELL AMENIA
Balancing Selection
gene brings some advantages to ‘make up’ for its lethal ness..in this case, sickle cell hosts have resistance to malaria