dominant

Examples of dominant in the following topics:

• Mendel's Law of Dominance

  • Rather than both alleles contributing to a phenotype, the dominant allele will be expressed exclusively.
  • It is sometimes convenient to talk about the trait corresponding to the dominant allele as the dominant trait and the trait corresponding to the hidden allele as the recessive trait.
  • For example, to say that "green peas" dominate "yellow peas" confuses inherited genotypes and expressed phenotypes.
  • Dominance is not inherent.
  • One allele can be dominant to a second allele, recessive to a third allele, and codominant to a fourth.

• Alternatives to Dominance and Recessiveness

  • The variant may be recessive or dominant to the wild-type allele.
  • In cases of multiple alleles, dominance hierarchies can exist.
  • In this case, the wild-type allele is dominant over all the others, chinchilla is incompletely dominant over Himalayan and albino, and Himalayan is dominant over albino.
  • These pink flowers of a heterozygote snapdragon result from incomplete dominance.
  • Discuss incomplete dominance, codominance, and multiple alleles as alternatives to dominance and recessiveness

• Life Cycles of Sexually Reproducing Organisms

  • The main categories of sexual life cycles in eukaryotic organisms are: diploid-dominant, haploid-dominant, and alternation of generations.
  • There are three main categories of life cycles in eukaryotic organisms: diploid-dominant, haploid-dominant, and alternation of generations.
  • Within haploid-dominant life cycles, the multicellular haploid stage is the most obvious life stage.
  • The third life-cycle type, employed by some algae and all plants, is a blend of the haploid-dominant and diploid-dominant extremes.
  • Fungi, such as black bread mold (Rhizopus nigricans), have haploid-dominant life cycles.

• Lethal Inheritance Patterns

  • In other instances, the recessive lethal allele might also exhibit a dominant (but not lethal) phenotype in the heterozygote.
  • Individuals with mutations that result in dominant lethal alleles fail to survive even in the heterozygote form.
  • Dominant lethal alleles are very rare because, as you might expect, the allele only lasts one generation and is not transmitted.
  • People who are heterozygous for the dominant Huntington allele (Hh) will inevitably develop the fatal disease.
  • Huntington's disease occurs when an abnormal dominant allele for the Huntington gene is present.

• The Punnett Square Approach for a Monohybrid Cross

  • The dominant seed color is yellow; therefore, the parental genotypes were YY (homozygous dominant) for the plants with yellow seeds and yy (homozygous recessive) for the plants with green seeds, respectively.
  • If the pattern of inheritance (dominant or recessive) is known, the phenotypic ratios can be inferred as well.
  • In a test cross, the dominant-expressing organism is crossed with an organism that is homozygous recessive for the same characteristic.
  • If the dominant-expressing organism is a homozygote, then all F1 offspring will be heterozygotes expressing the dominant trait.
  • A test cross can be performed to determine whether an organism expressing a dominant trait is a homozygote or a heterozygote.

• Mendel's Law of Segregation

  • Observing that true-breeding pea plants with contrasting traits gave rise to F1 generations that all expressed the dominant trait and F2 generations that expressed the dominant and recessive traits in a 3:1 ratio, Mendel proposed the law of segregation.
  • The allele that contains the dominant trait determines the phenotype of the offspring.
  • For the F2 generation of a monohybrid cross, the following three possible combinations of genotypes could result: homozygous dominant, heterozygous, or homozygous recessive.
  • Because heterozygotes could arise from two different pathways (receiving one dominant and one recessive allele from either parent), and because heterozygotes and homozygous dominant individuals are phenotypically identical, the law supports Mendel's observed 3:1 phenotypic ratio.

• Seedless Vascular Plants

  • The vascular plants, or tracheophytes, are the dominant and most conspicuous group of land plants.
  • The diploid sporophyte is the dominant phase of the life cycle , while the gametophyte is an inconspicuous, but still-independent, organism.
  • Throughout plant evolution, there is a clear reversal of roles in the dominant phase of the life cycle.
  • This life cycle of a fern shows alternation of generations with a dominant sporophyte stage.

• Garden Pea Characteristics Revealed the Basics of Heredity

  • Mendel's experiments with peas revealed the presence of dominant and recessive traits in the filial generations.
  • He called these, respectively, dominant and recessive traits.
  • Dominant traits are those that are inherited unchanged in a hybridization.
  • An example of a dominant trait is the violet-flower trait.
  • Moreover, the physical observation of a dominant trait could mean that the genetic composition of the organism included two dominant versions of the characteristic or that it included one dominant and one recessive version.

• Epistasis

  • The wild-type coat color, agouti (AA), is dominant to solid-colored fur (aa).
  • Epistasis can also occur when a dominant allele masks expression at a separate gene.
  • Finally, epistasis can be reciprocal: either gene, when present in the dominant (or recessive) form, expresses the same phenotype.
  • If the dominant allele for either of these genes is present, the result is triangular seeds.
  • In mice, the mottled agouti coat color (A) is dominant to a solid coloration, such as black or gray.

• Evolution of Reptiles

  • Dinosaurs and pterosaurs diverged from early amniotes and dominated the Mesozoic Era.
  • These groups remained inconspicuous until the Triassic period when the archosaurs became the dominant terrestrial group due to the extinction of large-bodied anapsids and synapsids during the Permian-Triassic extinction.
  • Dinosaurs dominated the Mesozoic Era, which was known as the "Age of Reptiles."
  • The dominance of dinosaurs lasted until the end of the Cretaceous period, the end of the Mesozoic Era.