Genetics: Gregor Mendel's Experiments

Consider two pure-breeding pea plants, one with inflated pods and axial flowers, and the other with constricted pods and terminal flowers. Assuming independent assortment and complete dominance (inflated and axial are dominant), what proportion of the F2 generation would phenotypically resemble the dihybrid cross's 'novel' phenotypes (constricted pods, axial flowers AND inflated pods, terminal flowers)?

In a scenario involving incomplete dominance, a cross between a homozygous red flower ($RR$) and a homozygous white flower ($WW$) yields all $RW$ offspring with pink flowers. If two $RW$ plants are crossed, what statistical test would most appropriately determine if the observed phenotypic ratios deviate significantly from Mendelian expectations, considering the presence of an intermediate phenotype?

A researcher is studying a population of wildcats in northeast Kansas, where coat color is determined by a single gene with incomplete dominance: $BB$ (blue), $bb$ (red), and $Bb$ (purple). Over several generations, the researcher observes a gradual shift in allele frequencies, with the blue allele ($B$) becoming increasingly rare. Ignoring any effects of mutations, migration, or selection, which evolutionary mechanism is most likely responsible for this shift, assuming the wildcat population is geographically isolated?

Consider a scenario where a plant species exhibits heterostyly (different style lengths) as a mechanism to promote outcrossing. In a population of these plants, a novel mutation arises that disrupts the heterostylous system, leading to increased self-pollination. What would be the most likely evolutionary consequence of this mutation on the genetic diversity and fitness of the plant population?

Imagine a population of pea plants where flower color is determined by a single gene with two alleles: $P$ (purple) and $p$ (white). A researcher collects data on flower color in this population over several generations and observes that the frequency of the $p$ allele decreases over time, even though the white flowers do not appear to have any obvious disadvantage. Which of the following scenarios could best explain this observation, considering factors beyond simple natural selection?

In a population of pea plants, the gene for plant height ($T$) exhibits complete dominance, with $T$ (tall) dominant over $t$ (dwarf). A large population of pea plants is sampled, and the following genotypic frequencies are observed: $TT$ = 0.49, $Tt$ = 0.42, $tt$ = 0.09. Assuming random mating, no selection, mutation, or gene flow, what is the predicted frequency of the $t$ allele in the next generation, based on the Hardy-Weinberg principle?

Consider a population of pea plants where seed color is determined by a single gene with two alleles: $Y$ (yellow) and $y$ (green). A researcher performs a series of crosses and observes that the offspring phenotypes do not consistently match the expected Mendelian ratios. Which of the following phenomena could explain this deviation, other than non-random mating, selection, or small sample size?

A geneticist discovers a novel mutation in pea plants that causes reduced pollen viability but also confers resistance to a previously devastating fungal pathogen. Under what conditions would this mutation most likely spread through a population of pea plants, assuming the pathogen is endemic?

A population of pea plants is established in a new habitat with limited resources. Initially, there is high phenotypic variation in plant height, ranging from very tall to very short. Over several generations, the population evolves towards an intermediate height, with the extreme phenotypes becoming less common. Which type of selection is most likely responsible for this evolutionary trend?

Consider a scenario where a population of pea plants is divided into several smaller, isolated subpopulations due to habitat fragmentation. Over time, the allele frequencies in these subpopulations diverge due to genetic drift. Which of the following outcomes is most likely to occur if these subpopulations are later reunited and allowed to interbreed freely, assuming no strong selection pressures?

A researcher discovers a coding mutation in pea plants that results in complete loss of function in a crucial enzyme required for chlorophyll synthesis. This mutation is recessive ($cc$). Despite the lack of chlorophyll (resulting in albino seedlings), the heterozygotes ($Cc$) appear phenotypically normal. If two heterozygotes happen to grow next to each other, and produce 100 seeds, what will likely happen?

In pea plants, axial flower position ($A$) is dominant to terminal ($a$). A plant breeder has a tall pea plant with axial flowers, but its exact genotype is unknown. To determine its genotype, the breeder crosses this plant with a dwarf plant with terminal flowers. Which of the following outcomes would definitively reveal that the tall, axial plant is heterozygous for both traits (i.e., $TtAa$), but assuming you don't know the linkage relationship of the genes?

A researcher investigates a novel trait in pea plants: resistance to a specific aphid species. She crosses a true-breeding resistant plant with a susceptible plant and finds that all the F1 offspring are resistant. However, when she crosses the F1 offspring with each other, the F2 generation shows a ratio of 15 resistant plants to 1 susceptible plant. What genetic phenomenon is most likely responsible for this inheritance pattern?

In a specific species of flowering plant, petal color is controlled by two genes, A and B. Gene A controls the production of a red pigment. The dominant allele A produces the pigment, while the recessive allele a does not. Gene B controls the deposition of the red pigment only if Gene A expresses. The dominant allele B allows deposition, while the recessive allele b blocks deposition. Furthermore, the epistatic function of B completely overrides any other expression if a plant has the aa genotype, resulting in no pigment. What phenotypic ratio would you expect in the F2 generation of a dihybrid cross (AaBb x AaBb)?

A population of pea plants exhibits a range of flower colors, influenced by several interacting genes. A plant breeder wants to create a true-breeding line with a specific, novel flower color that is not present in the current population. Which breeding strategy would be most effective in achieving this goal, assuming the desired color is determined by a complex combination of recessive alleles at multiple loci?

A researcher is studying a population of pea plants and discovers a new recessive mutation that causes the plants to be highly susceptible to a particular fungal disease. However, the heterozygous carriers of the mutation show slightly increased growth rates compared to homozygous wild-type plants in the absence of the disease. How would you describe this type of selection?

Assume flower color in a particular plant species is determined by two genes, R and W, following the pathway: Precursor --(Gene R)--> Intermediate --(Gene W)--> Pigment (color). Plants with the genotype $rr$ have white flowers because they cannot convert the precursor. Plants with the genotype $ww$ have pale flowers as they cannot efficiently convert the intermediate to pigment. In a cross between two plants heterozygous for both genes ($RrWw \times RrWw$), what proportion of the offspring would you expect to have pale flowers, assuming the genes assort independently?

Consider a plant species where fruit size is governed by three unlinked genes (A, B, and C), each with two alleles (A/a, B/b, C/c) that show additive effects. The more dominant alleles present, the larger the fruit. A plant with the genotype aabbcc has fruits weighing 20g, while a plant with the genotype AABBCC has fruits weighing 50g. What would be the expected weight of the fruits from a plant with the genotype AaBbCc?

Mendel's work laid the foundation for understanding patterns of inheritance. However, certain phenomena deviate from his laws. Which of the following conditions would MOST directly violate Mendel's Law of Independent Assortment?

In pea plants, the tall allele ($T$) exhibits complete dominance over the dwarf allele ($t$). A researcher crosses a tall plant of unknown genotype with a dwarf plant and obtains 50% tall offspring and 50% dwarf offspring. What is the genotype of the tall parent plant?

Consider the pedigree of a rare genetic disorder in a family. Several affected individuals are present in each generation, and both males and females are equally affected. However, affected fathers do not pass the trait to their sons. What is the most likely mode of inheritance for this disorder?

A researcher discovers a mutant allele in pea plants that causes wrinkled seeds. However, the wrinkled seed phenotype is only observed when the plants are grown at high temperatures. At lower temperatures, the mutant allele has no effect, and the seeds are round. What phenomenon is being observed?

In a population of pea plants, the frequency of the allele for yellow seeds ($Y$) is 0.6, and the frequency of the allele for green seeds ($y$) is 0.4. Assuming Hardy-Weinberg equilibrium, what percentage of the population is expected to be heterozygous ($Yy$)?

A researcher is studying a population of pea plants where seed color is determined by a single gene with two alleles: $Y$ (yellow) and $y$ (green). The researcher observes that certain individuals with the $Yy$ genotype have seeds that are mottled, with patches of both yellow and green color. Which genetic phenomenon is most likely responsible for this observation?

A plant breeder wants to develop a true-breeding line of pea plants that are both tall and have green seeds. However, these two traits are controlled by genes that are located close together on the same chromosome. What breeding strategy would be most effective in achieving this goal, and why?

A researcher is studying flower color inheritance in a certain plant species. She crosses a true-breeding plant with red flowers to a true-breeding plant with white flowers and obtains F1 offspring with pink flowers. When she intercrosses the F1 offspring, the F2 generation exhibits a phenotypic ratio of 1 red : 2 pink : 1 white. Which of the following experimental procedures could best confirm that flower color inheritance in this species is governed by a single gene with incomplete dominance?

Two seemingly identical varieties of true-breeding pea plants exhibit different heights when grown in different locations with varying soil conditions. However, within each location, the height differences between the varieties remain consistent over multiple generations. Which explanation best accounts for this observation?

A plant breeder crosses two true-breeding lines of pea plants: one with purple flowers and smooth seeds, and another with white flowers and wrinkled seeds. The F1 generation all has purple flowers and smooth seeds. However, when the F1 plants are testcrossed to a plant with white flowers and wrinkled seeds, the following progeny are obtained: 40% purple flowers, smooth seeds; 40% white flowers, wrinkled seeds; 10% purple flowers, wrinkled seeds; 10% white flowers, smooth seeds. Besides other more obvious factors, what accounts for this occurrence?