What does the notation TT mean to geneticists?
A two dominant alleles
B two recessive alleles
C at least one dominant allele
D one dominant and one recessive allele
The correct answer and explanation is:
The correct answer is A: two dominant alleles.
Explanation:
In genetics, the notation “TT” refers to the genotype of an organism and indicates that both alleles for a specific gene are dominant. Each gene is typically represented by a pair of alleles, one inherited from each parent. Alleles are versions of a gene, and they can be classified as dominant or recessive.
Dominant alleles are those that express their trait even when only one copy is present in a genotype. In contrast, recessive alleles require two copies to express their trait. When an individual has two dominant alleles for a particular gene, such as “TT,” the dominant trait associated with that gene will be expressed.
In this case, the individual’s genotype consists of two copies of the dominant allele, making it a homozygous dominant genotype. The term “homozygous” means that both alleles for the gene are the same, while “dominant” refers to the fact that the trait associated with these alleles will be observed.
For example, if the gene in question controls the flower color in plants and “T” represents the allele for red flowers (a dominant trait) and “t” represents the allele for white flowers (a recessive trait), then a plant with the genotype “TT” will have red flowers. The “T” allele dominates the expression of the color, and since both alleles are dominant, the plant will express the red flower color regardless of the presence of any other alleles.
If the genotype were “Tt” (heterozygous), the dominant trait would still be expressed, but the individual would carry a recessive allele, which could be passed on to offspring. However, in the case of “TT,” the organism is homozygous dominant, meaning there are no recessive alleles to pass on.