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Here we see a system where there are more than two morphs: the phenotypes A, B, AB and O are present in all human populations, but vary in proportion in different parts of the world. The phenotypes are controlled by multiple alleles at one locus. These polymorphisms are seemingly never eliminated by natural selection; the reason came from a ...
A notable example of this is Gregor Mendel's discovery that the white and purple flower colors in pea plants were the result of a single gene with two alleles. Nearly all multicellular organisms have two sets of chromosomes at some point in their biological life cycle ; that is, they are diploid .
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child.
The disease occurs more commonly in a distinct ethnic group (i.e., Africans, Asians, Caucasians etc.) The diseases may have more in common than generally recognized since similar risk factors are associated with multiple diseases. Families with close relatives are more likely to develop one of the disease than the common population.
The following are lists of animal diseases: This list is incomplete; you can help by adding missing items. (February 2021) List of aquarium diseases;
In medical genetics, compound heterozygosity is the condition of having two or more heterogeneous recessive alleles at a particular locus that can cause genetic disease in a heterozygous state; that is, an organism is a compound heterozygote when it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be ...
These genes display allelic heterogeneity at their loci and are responsible for distinct disease phenotypes. Some of these diseases include alkaptonuria, albinism, achondroplasia, and phenylketonuria. [2] [3] For example, β-thalassemia may be caused by several different mutations in the β-globin gene.
Not all heterozygotes for recessive lethal alleles will show a mutant phenotype, as is the case for cystic fibrosis carriers. If two cystic fibrosis carriers have children, they have a 25 percent chance of producing offspring having two copies of the allele, eventually resulting in the death of the child without intensive treatment. [9]