8 Complementation in Diploids Flashcards
Principle of Independent Assortment
2 genes on different chromosomes segregate (assort) independantly from one another in meiosis
Dihybrid cross that obeys Mendles principle of Independant Assortment ratio
9:3:3:1
Alternative to punnet squares
Branched line diagrams
Dihybrid Genotypic Ratios
Number of genotype classes = 3n
Where n = number of genes each with 2 alleles
Polygenetic inheritance
traits often controlled by more than 1 gene
Identification of more than 1 gene involved in controlling the same phenotypic trait
- Use mutational analysis to identify genes involved in controlling same trait
- Generate and ideantify sets of mutants
- What’s relationship between mutations involved in same phenotype
- Unknown mutant = X phenotype
- Different unknown mutant = X phenotype
So are these mutations in the same gene (complementation analysis is a key approach for this —> used in microbiology to determin metabolic pathways)
How would you determin whether the mutation in each strain is dominant or recessive?
Cross each mutation to wild-type, red strain and observe the phenotypes of progeny
If progeny shows red eyes - it’s recessive / if it shows brown eyes - muatation is dominant
Allelic mutations
Mutations that are members of the same complementation group
DIAGRAMS ON ONENOTE AND LECTURE SLIDES
X
Diploid complementation
No wild type allele for gene 1 so no complementation and a mutant phenotype
Relationship between number of complementation groups and number of genes affected
The number of different complementation groups = the number of genes affected
Summary
Different allelic forms of a gene can restore wild type phenotypes through complementation
However, the product of a gene may alter the action of another gene of phenotype
Epistasis - interaction between 2 or more genes to control a single phenotype
