Genotype And Phenotype/ Linkage Flashcards
What are the 3 dominance relationships between genotypes and phenotypes
Complete- where 1 allele clearly dominant and so offspring is replica of that allele/phenotype
Incomplete - where F1 offsprings don’t resemble either of parents (the dominance of the alleles not enough
Codominant - where both alleles are dominant to eachother and expressed in F1 phenotype
How is blood group A B O an example of codominance
There are 3 alleles for blood group
IO is recessive to IA and IB
IA and IB if present together are dominant and the blood group is AB
What is pleiotrophy
Where some genes or alleles can affect many characteristics at once
Eg in Manx cats the ML allele can disrupt spinal development (no tail) and another characteristic is its lethal, causing death if present twice
An epistatic gene is able to modify or mask phenotype as another genes expression is masked
What is the gene masked called
Hypostatic gene
What is penetrance as a principle
Sometimes a genotype doesn’t always show the same phenotype
Penetrance is how many members with a particular genotype (alleles) show the expected phenotype
Give an example of penetrance of the brca 1 gene
Brca is present in both men and women causing cancer, however the mutation is more likely to cause phenotype of cancer in men than women
What is it called when some disorders show different signs and symptoms in different people?
Variable expressivity
How is polydactyly an example of both incomplete penetrance and expressive variability
Incomplete penetrance- children with phenotype more likely to get it than parents with same genotype
Expressive variability - because it can affect either toes or hands
What else can affect penetrance and expressivity
Other genes or the environment
How are thermosensitve alleles an example of how environment affects expression
The alleles might not work depending on temperature
What is complementation analysis
Screening through mutants with same phenotype to see how many genes involved
What is complementation in a complementation analysis
When there are 2 genes involved in a phenotype/disorder and the offspring inherits them they don’t express the phenotype(not a mutant) - complementary genes
What is a complementation group
A set of mutations on the same chromosomal locus (same gene)
This does not cause complementation when crossed (still mutant)
What alleles need to be present for complementation analysis to work
A recessive allele
How would intragenic complementation affect complementation analysis
It wouldn’t work as complementation would occur even if mutations in 1 gene present
