Extension to Mendel's Rules I Flashcards
What is Cystic fibrosis?
Patients produce large quantities of thick, sticky mucous which plugs up airways and clogs ducts of glands such as the pancreas
What is dominance?
Dominance occurs when the phenotype of the heterozygote is the same as the phenotype of one of the homozygotes
Where is the gene responsible for cystic fibrosis?
On the long arm of chromosome 7
What is one of the more common genetic disorders among Caucasians and is usually considered to be a recessive disease?
Cystic fibrosis
What is the gene product of cystic fibrosis? What does the product do?
Cystic fibrosis transmembrane conductance regulator (CFTF)
Regulates movement of chloride ions into and out of cells
What does the mutated form of CFTR cause?
Channels to remain closed and chloride remains within cells
Those heterozygous with the cystic fibrosis trait, are they normal or do the have cystic fibrosis?
Heterozygotes produce both normal and mutated CFTR at the cellular level
So cellular level, this is co-dominance; but at phenotypic level, heterozygotes are normal
Incomplete dominance:
Phenotype of the heterozygote is intermediate (falls within the range) between the phenotypes of the two homozygotes
Penetrance:
Percentage of individuals having a specific genotype that expresses the expected phenotype
Expressivity:
The degree to which a character is expressed
Human polydactyly exhibits ______
Incomplete penetrance and variable expressivity
Epistasis:
it is the masking of one gene by another gene at a different locus
Epistatic gene:
Gene that does the masking
Hypostatic gene:
Gene that is masked
Dominant epistasis:
Homozygous dominant or heterozygous genotypes mask the effects of the hypostatic gene
