Based on this information, what is Smudge's phenotype for the body hair trait?
a hairless body a hairy body
In a group of cats, some individuals have a hairy body and others have a hairless body. In this group, the gene for the body hair trait has two alleles. The allele for a hairless body (b) is recessive to the allele for a hairy body (B).
Smudge is a cat from this group. Smudge has the homozygous genotype bb for the body hair gene.
All organisms have pieces of hereditary material called genes, which are passed from parents to offspring. Genes contain instructions for building the parts of an organism. An organism's genes affect its observable traits, including its appearance, its behavior, and which diseases it may have. Genes may have different alleles, or forms, that can cause different versions of a trait.
For example, flower color is a trait in pea plants. The gene for this trait has two possible alleles. Each allele is represented by an uppercase or lowercase letter. The allele F is for purple flowers, and the allele f is for white flowers. Each pea plant has two alleles for the flower color gene—one allele inherited from each parent.
An organism's genotype for a gene is its combination of alleles for that gene. So, a pea plant may have a genotype of FF, Ff, or ff for the flower color gene.
An organism's phenotype for a trait is its observable version of that trait, which depends on the organism's combination of alleles. A pea plant may have a phenotype of purple flowers or white flowers for the flower color trait.
Some traits, like flower color in pea plants, are controlled by a single gene. Most plants and animals have a genotype made up of two alleles for these traits. These two alleles determine whether an organism is homozygous or heterozygous for the gene.
An organism with two identical alleles for a gene is homozygous for that gene. A pea plant with the genotype FF or ff is homozygous for the flower color gene.
An organism with two different alleles for a gene is heterozygous for that gene. A pea plant with the genotype Ff is heterozygous for the flower color gene.
The types of alleles in an organism's genotype determine the organism's phenotype. Some alleles have types called dominant and recessive. These two types can cause different versions of a trait to appear as the organism's phenotype.
A dominant allele causes its version of the trait to appear even when the organism also has a recessive allele for the gene. In pea plants, the F allele, which causes purple flowers, is dominant over the f allele. A pea plant with at least one F allele will have the F allele's version of the flower color trait. So, a plant with the genotype FF or Ff will have purple flowers.
A recessive allele causes its version of the trait to appear only when the organism does not have any dominant alleles for the gene. In pea plants, the f allele, which causes white flowers, is recessive to the F allele. A pea plant with only f alleles will have the f allele's version of the flower color trait. So, a plant with the genotype ff will have white flowers.
Smudge's genotype for the body hair gene is bb. Smudge's genotype of bb has only b alleles. The b allele is for a hairless body. So, Smudge's phenotype for the body hair trait must be a hairless body.
To check this answer, consider whether Smudge's alleles are dominant or recessive. The allele for a hairless body (b) is recessive to the allele for a hairy body (B). This means B is a dominant allele, and b is a recessive allele.
Smudge's genotype of bb has only recessive alleles. An organism with only recessive alleles for a gene will have the recessive allele's version of the trait. So, Smudge's phenotype for the body hair trait must be a hairless body.