Heredity and Variation

Match each specified plant genotype with the number of genetically distinct gamete types it can produce during meiosis according to Mendel's Law of Independent Assortment.

In guinea pigs (*Cavia porcellus*), black coat color ($B$) is dominant over white coat color ($b$), and short hair ($S$) is dominant over long hair ($s$). If a heterozygous black, short-haired guinea pig ($BbSs$) is mated with a white, long-haired guinea pig ($bbss$) and they produce a total of 640 offspring, how many of the offspring are expected to display a black coat and long hair?

A botanical study recorded two phenotypic traits in a population of *Hibiscus sabdariffa*: total leaf surface area (measured in $\text{cm}^2$) and petal pigmentation pattern (either solid crimson or white-striped). Leaf surface area exhibited a smooth, bell-shaped frequency distribution curve across the population, with mean values altering significantly when cloned specimens were grown in nutrient-deficient versus nutrient-rich soils. In contrast, petal pigmentation pattern showed strict discrete categories with no intermediate forms, remaining completely unchanged across different soil conditions. Which of the following statements correctly explains the biological mechanisms responsible for the variation observed in these two traits?

In humans, normal skin pigmentation is governed by a dominant allele ($A$), while albinism is caused by a recessive allele ($a$). Match each parental cross combination on the left with its corresponding expected offspring phenotypic and genotypic outcome on the right according to Mendel's First Law.

A geneticist analyzed the phenotypic distribution of two traits in a population of fruit flies (*Drosophila melanogaster*): wing length measured in millimeters and eye color (red versus white). When cultures were reared across a range of ambient temperatures, the wing lengths across the population formed a smooth spectrum whose mean value shifted significantly with temperature changes. In contrast, eye color consistently segregated into two discrete, non-overlapping categories in predictable Mendelian ratios regardless of rearing temperature. What does this observation indicate regarding the genetic control and environmental sensitivity of these two traits?

The human ABO blood group system is classified as a morphological trait that displays continuous variation across a population.

Phenotypic traits exhibiting discontinuous variation, such as human ABO blood groups and tongue-rolling ability, are controlled by polygenic inheritance and show a continuous spectrum of intermediates modified by environmental factors.

Match each sex-linked inheritance pattern or sex determination concept on the left with its correct biological description on the right.

In maize plants (*Zea mays*), the allele for purple kernels ($P$) is completely dominant to the allele for yellow kernels ($p$). A true-breeding purple-kernel plant is crossed with a true-breeding yellow-kernel plant. If the $F_1$ plants are self-pollinated, what is the expected genotypic ratio in the $F_2$ generation?

In diploid eukaryotic organisms, genetic information is organized into chromosomes containing specific functional sequences. Which of the following statements accurately describes the biological distinction between alleles and gene loci during meiotic division?

In maize (*Zea mays*), the allele for starchy endosperm ($Su$) is completely dominant over the allele for sugary endosperm ($su$). Based on Mendel's First Law (Law of Segregation), which expected progeny outcome on the right correctly matches each monohybrid parental cross scenario on the left?

Human physiological traits such as blood pressure and resting pulse rate exhibit discontinuous variation because individuals strictly belong to distinct, non-overlapping phenotypic categories controlled solely by single-gene inheritance.

Human skin color exhibits continuous variation because it is governed by polygenic inheritance with additive gene action, allowing environmental exposure to modify phenotypic expression along a continuous spectrum, whereas discontinuous traits like the ABO blood group system are controlled monogenically and are exempt from environmental modification.

In humans, hypertrichosis of the ear pinna is a Y-linked (holandric) trait, whereas red-green color blindness is an X-linked recessive disorder ($X^c$). A man with hypertrichosis and normal vision marries a phenotypically normal woman whose father was color-blind. What is the probability that their first child will be a male displaying both hypertrichosis and red-green color blindness?

Match each sex determination mechanism or sex-linked trait concept on the left with its corresponding biological description on the right.

A mother with blood group B gives birth to a child with blood group O. An alleged father involved in a paternity case has blood group AB. Based on the genetic principles of codominance and multiple alleles governing the ABO blood group system, which of the following conclusions regarding paternity is correct?

Agricultural plant breeders often cross two genetically distinct inbred lines of maize to produce offspring that display superior growth rate, pest resistance, and crop yield compared to either parent. Which of the following biological terms best describes this application of genetics?

A geneticist crosses two heterozygous tall pea plants ($Tt$). In the resulting offspring, some plants display the dwarf trait even though both parent plants were tall. Which genetic principle best explains why the dwarf trait was masked in the parent generation?

A woman who is a carrier for red-green colour blindness ($X^C X^c$) marries a man with normal colour vision ($X^C Y$). What is the probability that any son born to this couple will be colour-blind?

During a genetic survey of a fruit fly (*Drosophila melanogaster*) population, scientists observed variations in eye color caused by different molecular versions of the gene controlling pigment production located at the same locus on homologous chromosomes. Which term correctly identifies these alternative functional forms of a single gene?