Final answer:
Offspring exhibit recessive traits when they are homozygous (bb) for that gene. In a Punnett square for a cross of two heterozygotes (Bb), only the 'bb' offspring will demonstrate the recessive trait according to Mendelian genetics.
c is correct
Step-by-step explanation:
Recessive traits will be exhibited by offspring that are homozygous for that trait. This means that an individual must have two copies of the recessive gene, represented as 'bb', to exhibit the recessive phenotype. In Mendelian genetics, when a gene is represented by two different alleles, such as 'B' for the dominant allele and 'b' for the recessive allele, the recessive trait only appears in the phenotype when both alleles are recessive (bb). If we consider a Punnett square showing a cross between two heterozygotes (Bb), the offspring possibilities are 'BB', 'Bb', 'bB', and 'bb'. Only the 'bb' offspring will display the recessive trait.
For example, in the case of cleft chin versus smooth chin, if 'B' represents the dominant allele for a cleft chin and 'b' represents the recessive allele for a smooth chin, only individuals with 'bb' genotype will have a smooth chin. According to Mendel's law of dominance, in the case of a heterozygous pairing (Bb), the dominant trait (cleft chin) will be expressed, masking the presence of the recessive trait (smooth chin). This principle is also applicable to other traits such as flower color in pea plants, where a similar 3:1 ratio occurs in a monohybrid cross between heterozygous parents.
Thus, in response to the question, option 'c. homozygous' is correct for those statements where a recessive trait will be observed in individuals that are homozygous for that trait.