Heredity and Variation

Which of the following human traits represents a physiological variation rather than a morphological variation?

An allele whose phenotype is expressed in an organism only when two copies of it are present, and whose effect is masked in the presence of a contrasting allele, is best described as which of the following?

In a diploid eukaryotic organism, alternative forms of a single gene (alleles) controlling a specific trait occupy different loci on non-homologous chromosomes.

In sorghum plants, tall stem height ($T$) is completely dominant over dwarf stem height ($t$). In a monohybrid cross between two heterozygous tall plants ($Tt \times Tt$), the conditional probability that a plant displaying the tall phenotype is homozygous dominant ($TT$) is $1/3$.

In pea plants, the allele for green pod color ($G$) is completely dominant over the allele for yellow pod color ($g$). What is the expected genotypic ratio of the offspring when two heterozygous green-podded plants ($Gg$) are crossed?

In a monohybrid cross between two heterozygous green-pod pea plants ($Gg$), Mendel's Law of Segregation predicts that $75\%$ of the $F_2$ offspring will possess the heterozygous ($Gg$) genotype.

Pair each basic genetic term listed on the left with its correct biological description on the right.

In genetics, an organism's traits are determined by its underlying genetic composition as well as its interaction with the environment. Which term specifically describes the observable physical, physiological, or behavioral characteristics of an organism?

In fruit flies (*Drosophila melanogaster*), the allele for normal wings ($V$) is completely dominant over the allele for vestigial wings ($v$). Match each parental cross listed on the left with its corresponding expected offspring phenotypic or genotypic ratio on the right.

In rabbits, the allele for short hair ($H$) is completely dominant over the allele for long hair ($h$). A pure-breeding long-haired female rabbit is crossed with a heterozygous short-haired male rabbit to produce an $F_1$ generation. If two short-haired offspring from this $F_1$ generation are subsequently mated to produce an $F_2$ generation, what is the expected ratio of homozygous dominant to heterozygous genotypes strictly among the short-haired $F_2$ individuals?

In human genetics, the ABO blood group system is controlled by multiple alleles ($I^A$, $I^B$, and $i$). Which of the following blood group phenotypes directly demonstrates codominance between alleles?

In a dihybrid organism with the genotype $AaBb$, the two gene pairs assort independently during meiosis according to Mendel's Second Law. What is the expected phenotypic or genotypic ratio of the gametes produced by this individual?

In garden pea plants (*Pisum sativum*), tall stem height ($T$) is dominant over dwarf stem height ($t$), and yellow seed color ($Y$) is dominant over green seed color ($y$). According to Mendel's Law of Independent Assortment, how many genetically distinct types of gametes can be produced by an $F_1$ plant with the genotype $TtYy$?

In watermelon plants (*Citrullus lanatus*), solid green rind color ($G$) is dominant over striped rind color ($g$), and short fruit shape ($R$) is dominant over long fruit shape ($r$). If a watermelon plant heterozygous for both traits ($GgRr$) is self-pollinated and yields $800$ offspring, how many of these offspring are expected to possess solid green rind and long fruit shape?

In cattle, coat color is determined by a single gene exhibiting complete dominance, where the allele for black coat ($B$) is dominant over the allele for red coat ($b$). Match each monohybrid cross scenario with its correct genotypic or phenotypic outcome outcome/deduction.

In guinea pigs, the allele for a rough coat ($R$) is completely dominant over the allele for a smooth coat ($r$). A monohybrid cross is performed between two heterozygous rough-coated parents ($Rr \times Rr$). What is the expected ratio of homozygous dominant individuals to heterozygous individuals among the offspring possessing the rough coat phenotype?

A man with blood group AB ($I^A I^B$) marries a woman with blood group A who is heterozygous ($I^A i$). What is the probability that their first child will have blood group A?

In sweet pea plants (*Lathyrus odoratus*), purple flower color ($P$) is dominant over red flower color ($p$), and long pollen grain ($L$) is dominant over round pollen grain ($l$). If a heterozygous dihybrid plant with the genotype $PpLl$ is self-pollinated and yields a total of $160$ F2 seeds, how many of these seeds are expected to produce plants with the double recessive phenotype of red flowers and round pollen grains?

In domestic fowl (*Gallus gallus*), rose comb ($R$) is dominant over single comb ($r$), and feathered legs ($F$) are dominant over clean legs ($f$). A rooster heterozygous for both traits ($RrFf$) is test-crossed with a hen possessing a single comb and clean legs ($rrff$). If a total of $400$ chicks are hatched from this cross, how many are expected to exhibit a rose comb and clean legs?

Match each dihybrid parental cross genotype involving independently assorting genes with its corresponding expected phenotypic ratio in the offspring.