What term is used to describe the genetic makeup of an organism, which includes all the alleles inherited from its parents?
Phenotype
Genotype
Allele
Locus
Correct Answer:B
Explanation
The correct option is B. Genotype.
Detailed Explanation:
Definition of Genotype: The term "genotype" refers to the genetic constitution of an organism. It encompasses all the alleles (versions of genes) that an organism inherits from its parents. For example, if a plant has one allele for tallness (T) and one for shortness (t), its genotype would be represented as Tt.
Understanding Alleles: Alleles are different forms of a gene that can exist at a specific locus (position) on a chromosome. Each individual inherits two alleles for each gene, one from each parent. The combination of these alleles determines the organism's genotype.
Contrast with Phenotype: The phenotype is the observable physical or biochemical characteristics of an organism, which result from the interaction of its genotype with the environment. For instance, the phenotype could be tall or short in the example above, but the genotype (Tt, TT, or tt) describes the underlying genetic information.
Locus: A locus (plural: loci) refers to the specific physical location of a gene or allele on a chromosome. It is not a term that describes the genetic makeup itself but rather the position where a gene is found.
Why Other Options Are Incorrect:
A. Phenotype: This option is incorrect because it describes the physical expression of the genotype, not the genetic makeup itself. The phenotype is influenced by the genotype but does not represent the genetic information.
C. Allele: While alleles are components of the genotype, they are not synonymous with the entire genetic makeup. An allele is just one variant of a gene, whereas the genotype includes all alleles for all genes in an organism.
D. Locus: This term refers to the specific location of a gene on a chromosome and does not describe the genetic makeup of an organism. It is a term used in genetics to pinpoint where a gene is located, not to define the genetic composition.
Summary of Key Points:
Genotype is the complete set of alleles inherited from parents, defining the genetic makeup of an organism.
Phenotype is the observable traits resulting from the genotype and environmental interactions.
Alleles are variations of a gene, while locus refers to the specific location of a gene on a chromosome.
Understanding these terms is crucial for studying genetics and how traits are inherited.