BIOL 1001 Chapter : Ch 10 1 10 5 Notes
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Inheritance- the process by which the characteristics of an individual are passed on to their offspring. Alleles- different versions of a gene at a given locus: mutations are the source of alleles. A diploid organism has two copies of each gene, one on each homologous chromosome. Homozygous- both homologues have the same allele at a given locus. Heterozygous- two homologues have different alleles at a given locus: heterozygotes are often called hybrids. Genotype- the combination of alleles carried by an organism. Gregor mendel and his peas ( mid 1800"s, before the discovery of dna, chromosomes, or meiosis) Mendel opened up the flowers and performed experiments using cross- fertilization. True-breeding organisms that are homozygous for a particular trait: self fertilization of true breeding pea plants will always produce the same phenotype. Mendel had populations pea plants that were true-breeding for a particular trait. He cross-fertilized these plants and counted the numbers of offspring that had particular traits.
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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. |