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If overdominance is the main cause for the fitness advantages of heterosis, then there should be an over-expression of certain genes in the heterozygous offspring compared to the homozygous parents. On the other hand, if dominance is the cause, fewer genes should be under-expressed in the heterozygous offspring compared to the parents.
In the first hypothesis, if individuals heterozygous at the MHC are more resistant to parasites than those that are homozygous, then it is beneficial for females to choose mates with MHC genes different from their own, and would result in MHC-heterozygous offspring—this is known as disassortative mating.
All offspring of an affected individual are either heterozygous or homozygous for the mutated allele. Consequently, all unaffected (heterozygous) offspring of an affected individual are obligate carriers of the disease because they will necessarily carry the mutated allele.
However, convincing evidence indicates, in areas with persistent malaria outbreaks, individuals with the heterozygous state have a distinct advantage (and this is why individuals with heterozygous alleles are far more common in these areas). [13] [14] Those with the benign sickle trait possess a resistance to malarial infection. The pathogen ...
The offspring make up the first filial generation. Every member of the F1 generation is heterozygous and the phenotype of the F1 generation expresses the dominant trait. [3] Crossing two members of the F1 generation produces the second filial (F2) generation.
The words homozygous, heterozygous, and hemizygous are used to describe the genotype of a diploid organism at a single locus on the DNA. Homozygous describes a genotype consisting of two identical alleles at a given locus, heterozygous describes a genotype consisting of two different alleles at a locus, hemizygous describes a genotype consisting of only a single copy of a particular gene in an ...
Therefore, a cross between a homozygous dominant and a homozygous recessive organism yields a heterozygous organism whose phenotype displays only the dominant trait. The F 1 offspring of Mendel's pea crosses always looked like one of the two parental varieties. In this situation of "complete dominance", the dominant allele had the same ...
In the example on the right, both parents are heterozygous, with a genotype of Bb. The offspring can inherit a dominant allele from each parent, making them homozygous with a genotype of BB. The offspring can inherit a dominant allele from one parent and a recessive allele from the other parent, making them heterozygous with a genotype of Bb.