Question

The growth of scurs, small horn-like growths on the faces of cattle, is inherited with the sex influenced alleles Sc and sc. The trait is dominant in males and recessive in females. If an animal is heterozygous for these alleles, it will?

1) Express the dominant trait
2) Express the recessive trait
3) Express a combination of the dominant and recessive traits
4) Cannot be determined

Answer 1

In heterozygous cattle, males will express the dominant trait of scurs, while females will express the recessive trait, with scurs not developing, due to sex-influenced traits being dependent on the sex of the animal.

Step-by-step explanation:

If an animal is heterozygous (Scsc) for the alleles that control scurs in cattle, males will express the dominant trait (Scurs), while females will express the recessive trait (no scurs) due to the sex-influenced pattern of inheritance.

The inheritance of scurs in cattle is an example of sex-influenced traits, where the expression of a trait differs between males and females. A heterozygous animal possesses one copy of the dominant allele (Sc) and one copy of the recessive allele (sc). In males, the Sc allele is dominant, resulting in the presence of scurs, even if there is only one copy of the Sc allele. However, in females, the expression of scurs is recessive, meaning that a female would only have scurs if she was homozygous for the dominant allele (ScSc). This means that, for a heterozygous female (Scsc), the scurs would not develop since she has only one dominant allele and it does not express in females unless two copies are present. This phenomenon is due to hormonal differences between genders, which influence the expression of certain genes. Thus, the expression of scurs in heterozygous cattle depends on the sex of the animal, demonstrating that some genetic traits are not simply dominant or recessive but are instead influenced by the sex of the organism.