GED Science › Alleles and Genes
What word is used to describe an organism with two copies of the same allele?
Homozygous
Hybrid
Heterozygous
Carrier
When an organism has only one type of allele for a given gene, it is described as homozygous ("homo-" meaning one). Organisms can be either homozygous dominant, meaning they have two dominant alleles, or homozygous recessive, meaning they have two recessive alleles.
A heterozygote, or hybrid, has two different types of alleles for a given gene. When the dominant allele causes the recessive trait not to be represented in the phenotype, the organism is considered a carrier for the recessive trait.
Which of the following statements about alleles is correct?
Alleles represent different forms of the same gene
Alleles represent the same forms of different genes
Humans have only one allele for each gene
A homozygous genotype will have two different alleles present
A heterozygous genotype will have only one type of allele present
Alleles are different forms of the same gene. For example, the gene for flower color in a plant may come in two allele varieties: white or purple. Both alleles code for flower color (the same gene), but represent different types of the genetic expression.
Humans are diploid organisms, meaning that they carry two alleles for each gene, one from each parent. Organisms with two copies of the same allele are considered homozygous, while those with copies of two different alleles are considered heterozygous.