Beyond Mendelian Genetics Flashcards
T/F All Mandelian monohybrid crosses are simple.
FALSE!
What are 5 possible complicators of crosses?
CLIMP
Incomplete Dominance Co-Dominance Multiple Alleles Polygenic Traits Lethal Dominant Traits
This situation features a recessive allele which is not completely hidden.
Incomplete Dominance
If there is no dominant allele we have:
Incomplete Dominance
Phenotypic ratio in F2 generation with incomplete dominance?
1:2:1
This situation entails 2 possible alleles for a different gene.
Multiple Alleles
A good example of Multiple Alleles is:
ABO Blood Types!
Blood types are determined by presence of:
CHO on RBC surface.
The multiple alleles in blood types are:
IA & IB (Codominant), both dominant to i
In co-dominance we have…
No dominant allele, No intermediate phenotypes
A prime example of co-dominance =
Sickle Cell Anemia!
Always in co-dominance we have…
Half of one phenotype, half of the other
In this situation we have multiple genes affecting a single trait:
Polygenic Traits
In polygenic traits there are more than _ alleles that are contributing to each gene.
2
Example of polygenic traits?
Human skin pigmentation, 3 Melanin genes
T/F In polygenic traits we have less dominant alleles.
FALSE - More dominant alleles
Most genetic disorders come from..
Homozygous Recessive Genes (Some co-dominant)
In the case of a dominant allele which causes disease we have a…
Lethal Dominant Gene
In a Lethal Dominant Gene:
One mutant allele can lead to disease. 2 will be fatal.
If heterozygous dominant?
Lethal = fetus will die in utero
If the homozygous dominant is fatal?
Partial lethal dominance
Therefore, heterozygous with one dominant and one recessive can:
Survive!
Example of Partial Lethal Dominance?
Achondroplastic Dwarfism
In achondroplastic dwarfism AA= Aa= aa=
Aa= Dwarf aa= Average Height AA = lethal!
Phenotypic & genotypic ratio in partial lethal dominance?
Phenotypic
2:1
Genotypic
1:2:1 (Count fatal as possible outcome!)
In Complete Lethal Dominance, Homozygous Dominant:
Die in utero
Heterozygous?
Die in utero
Example of complete lethal dominance?
Huntingtons Disease
T/F There are several completely lethal dominant diseases.
FALSE
What makes Huntington’s common?
Most have offspring before they know, as later onset (35-45)
