Genetics: Incomplete Dominance and Overdominance

An intermediate phenotype between the two homozygotes.

The four o’clock plant exhibits pink flowers (CRCW) due to the mixing of the red (CR) and white (CW) traits.

The expected phenotypic ratio is 1:2:1.

<p>Microscopic examination shows that the round pea trait (R) exhibits incomplete dominance with respect to starch biosynthesis.</p> Signup and view all the answers

<p>The individual displays wavy hair.</p> Signup and view all the answers

<p>The genotypic ratio is 1:2:1.</p> Signup and view all the answers

<p>A phenotype is defined by the observable traits resulting from the mixing of alleles in the heterozygote.</p> Signup and view all the answers

<p>Dominance may change when traits are closely examined, revealing complexities such as incomplete dominance.</p> Signup and view all the answers

<p>Overdominance occurs when a heterozygote has greater reproductive success than either homozygote, illustrating the concept of heterozygote advantage.</p> Signup and view all the answers

<p>Individuals with the HbS allele suffer from sickle-cell anemia, which shortens their lifespan, but those with the HbAS genotype may have protection against malaria, highlighting the advantages of heterozygosity.</p> Signup and view all the answers

<p>The two major consequences are a shortened lifespan of red blood cells, resulting in anemia, and clumping of sickle cells, which blocks capillary circulation.</p> Signup and view all the answers

<p>Co-dominance results in the offspring displaying both white and black feathers independently.</p> Signup and view all the answers

<p>Sex-influenced traits are dominant in one sex and recessive in the other, while sex-limited traits affect only one sex regardless of genotype.</p> Signup and view all the answers

<p>Co-dominance is when both alleles in a heterozygote are expressed equally, without one being dominant over the other, unlike typical dominance where one allele masks the effect of the other.</p> Signup and view all the answers

<p>Scurs in cattle are a sex-influenced trait where the allele is dominant in males but recessive in females.</p> Signup and view all the answers

<p>The presence of both HbA and HbS alleles in some individuals results in a survival advantage against malaria, demonstrating overdominance as these heterozygotes show greater fitness than either homozygote.</p> Signup and view all the answers

<p>Blood type O does not express when A and B genes are present, indicating that A and B are dominant over O.</p> Signup and view all the answers

<p>When black and white animals breed, co-dominance results in offspring with both black and white spots.</p> Signup and view all the answers

<p>Complementation is a phenomenon where two different parents with similar recessive phenotypes produce offspring with a wild-type phenotype due to contributions from different genes.</p> Signup and view all the answers

<p>Gene modification occurs when an allele of one gene influences the phenotypic expression of alleles from another gene.</p> Signup and view all the answers

<p>Gene redundancy refers to the situation where the loss of function in one gene does not affect the phenotype, but the loss of function in two genes does result in an observable effect.</p> Signup and view all the answers

<p>When two genes complement each other, it means that the mutations are in different genes, allowing for the contribution of a wild-type allele from each parent.</p> Signup and view all the answers

<p>Epistasis is a genetic interaction where the phenotypic effects of one gene are masked by another gene, leading to alterations in observed traits.</p> Signup and view all the answers

<p>'cc' produces no functional enzyme C, and 'pp' produces no functional enzyme P, which both stop the production of purple pigment.</p> Signup and view all the answers

<p>Epistatic interactions typically arise when two different proteins are involved in a common cellular function, such as in an enzymatic pathway.</p> Signup and view all the answers

<p>Dominance refers to the interaction between alleles of the same gene, whereas epistasis involves the interactions between alleles of two different genes.</p> Signup and view all the answers

<p>Lethal alleles are usually inherited in a recessive manner and may lead to deviations from expected Mendelian ratios due to the absence of certain genotypes in the offspring.</p> Signup and view all the answers

<p>Pleiotropy is when a single gene influences multiple phenotypic traits. An example is the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which affects lung function, digestion, and sweat characteristics.</p> Signup and view all the answers

<p>Conditional lethal alleles cause death only under specific environmental conditions, while semilethal alleles kill only a portion of the population.</p> Signup and view all the answers

<p>An example of a sex-limited trait is the ornate plumage of roosters, which is significant as it demonstrates sexual dimorphism in birds.</p> Signup and view all the answers

<p>Essential genes are required for survival, and mutations in these genes can lead to the formation of lethal alleles, resulting in death.</p> Signup and view all the answers

<p>Gene interactions occur when multiple genes affect a single trait, leading to variations in characteristics such as height and pigmentation influenced by both genetic and environmental factors.</p> Signup and view all the answers

<p>Embryonic development influences coat color patterns through the expression of genes like MITF, which affects the migration and survival of melanoblasts.</p> Signup and view all the answers

<p>Epistasis is when the alleles of one gene mask or alter the phenotypic effects of alleles from another gene, influencing phenotypic ratios in genetic crosses.</p> Signup and view all the answers

<p>Lethal alleles can prevent cell division, potentially causing death at an early developmental stage or later in life.</p> Signup and view all the answers

<p>Mutations in nonessential genes may not lead to death but can still benefit the organism, while mutations in essential genes usually result in lethal alleles that affect survival.</p> Signup and view all the answers

<p>Sexual dimorphism in humans is primarily due to the presence of reproductive organs such as ovaries in females and testes in males.</p> Signup and view all the answers

<p>The dominant mutation in Manx cats shortens the tail but is lethal when homozygous, thus those individuals do not survive.</p> Signup and view all the answers

<p>Temperature-sensitive lethal alleles result in the death of an organism under specific temperature conditions, often due to misfolded proteins at higher temperatures.</p> Signup and view all the answers

<p>Overdominance occurs when heterozygotes have greater reproductive success than either homozygote. Benefits may include increased resistance to infections, enhanced protein function, or broader protein functionality.</p> Signup and view all the answers

<p>Codominance is when heterozygotes express both alleles simultaneously without forming an intermediate phenotype. An example is the AB blood type, where both A and B alleles are expressed.</p> Signup and view all the answers

<p>Sex-influenced inheritance refers to alleles that may be recessive in one sex and dominant in the opposite sex. This pattern is influenced by sex hormones affecting gene expression.</p> Signup and view all the answers

<p>Sex-limited inheritance occurs when a trait is expressed in only one sex. An example is the development of mammalian breasts, which typically occurs in females.</p> Signup and view all the answers

<p>Lethal alleles are those that can cause the death of an organism, often resulting from loss-of-function mutations in essential proteins. These mutations can lead to detrimental phenotypes.</p> Signup and view all the answers

<p>Sex hormones can regulate the molecular expression of genes, affecting whether an allele is dominant or recessive in a given sex. This can lead to different phenotypic outcomes.</p> Signup and view all the answers

<p>In overdominance, heterozygotes may produce proteins that enhance function or provide wider functionality, contributing to their reproductive success. This can include resistance to diseases.</p> Signup and view all the answers

<p>Codominance allows for the expression of both alleles, resulting in traits that may provide a fitness advantage or better adaptability in varying environments. It leads to greater phenotypic diversity.</p> Signup and view all the answers