BIOL 1090 Chapter Notes - Chapter 2: Gregor Mendel, Punnett Square, Mutual Exclusivity
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3 May 2019
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3. 1 gregor mendel discovered the basic principles of heredity. At each locus, a diploid organism possesses two alleles located on different homologous chromosomes. The genotype is the set of alleles that an individual organism possesses. A diploid organism with a genotype consisting of two identical alleles is homozygous at that locus. One that has a genotype consisting of two different alleles is heterozygous at the locus. A phenotype is the manifestation or appearance of a characteristic. 3. 2 monohybrid crosses reveal the principle of segregation and the. Monohybrid crosses: crosses between parents that differed in a single characteristic. Each individual diploid organism possesses two alleles for any particular characteristic, one inherited from the maternal parent and one from the paternal parent-these two alleles segregate or separate when gametes are formed, and one allele goes into each gamete. The two alleles segregate into gametes in equal proportions.
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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. |