BI226 Lecture Notes - Lecture 1: Abo Blood Group System, Hh Blood Group, Wild Type
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Document Summary
Inheritance patterns of single genes and gene interaction. Interactions between alleles produce dominance relationships: mendel examine traits with only two alternate forms, in each test, one trait had complete dominance, so heterozygous individuals showed the dominant trait. Null mutations/amorphic mutations: no functional gene product typically lethal in homozygous form. Leaky/hypomorphic mutations: partial loss of function: severity of phenotype depends on level of activity, gain of function: new function or increased wild-type activity. Hypermorphic: produce more gene activity than usual. Incomplete dominance: when one allele is not completely dominant over the other, we start using notation as. The bombay phenotype: when someone has a type a, type b, or type ab blood type but the h antigen is not completely formed, and so no antigens are created, causing the person to express a. Type o blood type with type o antibodies. Huntington disease: heterozygote form allows onset of disease to be delayed until adult hood.
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Related Questions
These all relate to exceptions to the inheritance patterns encountered by Mendel.â
Why do multiple and lethal alleles often result in modifications of the classic Mendelian monohybrid and dihybrid ratios?
Select the four correct statements.
-When an essential gene is mutated, it can result in a lethal phenotype. There are no classic Mendelian monohybrid and dihybrid ratios. |
-In the case of codominance, heterozygotes produce gene products from both alleles of a gene. Classic Mendelian monohybrid and dihybrid ratios are modified by codominance. |
-In the case of incomplete dominance, the phenotype of the heterozygote is distinct from and often intermediate to the phenotypes of homozygous individuals. Classic Mendelian monohybrid and dihybrid ratios are modified by incomplete dominance. |
-Genes exist in a large number of allelic versions and a diploid organism has two homologous gene loci that may be occupied by different alleles of the same gene. This can result in many different phenotypes for traits, which may not follow typical Mendelian ratios. |
-When an essential gene is mutated, it can result in a lethal phenotype. This results in a modification of classic Mendelian ratios. |
-The phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. The joint expression of both alleles in a heterozygote is called codominance. There are no classic Mendelian monohybrid and dihybrid ratios. |
-Genes exist in a large number of allelic versions, but in a diploid organism, only one allele of the gene can occupy one homologous gene loci. Classic Mendelian inheritance cannot explain this phenomenon. |
-Each gene produces a unique gene product. The effect of one allele in a heterozygote completely masks the effect of the other. Classic Mendelian genetics cannot explain this phenomenon. |