BIOL 1201 Chapter : Ch 14
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Father of genetics: gregor mendel, a monk who was trained in science at the university of vienna, pea plant patterns, able to predict phenotype of future offspring. Homologous chromosomes carry the same kinds of genes for the same characteristics. Genes for the same characteristics are found at the same loci on both homologous chromosomes. The particular combination of the 2 alleles carried by an individual is called the genotype: physical expression of genotype is phenotype (purple vs white, genotype determines phenotype. How is sex determined in the offspring: mammals have a set of sex chromosomes that dictate gender, non sex chromosomes occur in identical pairs called autosomes. Many traits do not follow simple mendelian rules of inheritance: not all traits completely controlled by a single gene, trait may not be completely dominant to another. The information content of dna is in the form of specific sequences of nucleotides: dna codes for proteins.
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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. |