GED Science : Alleles and Genes

Study concepts, example questions & explanations for GED Science

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Example Questions

Example Question #1 : Alleles And Genes

Which of the following statements about alleles is correct?

Possible Answers:

A heterozygous genotype will have only one type of allele present

A homozygous genotype will have two different alleles present

Humans have only one allele for each gene

Alleles represent different forms of the same gene

Alleles represent the same forms of different genes

Correct answer:

Alleles represent different forms of the same gene

Explanation:

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.

Example Question #1 : Alleles And Genes

What word is used to describe an organism with two copies of the same allele?

Possible Answers:

Heterozygous

Hybrid

Homozygous

Carrier

Correct answer:

Homozygous

Explanation:

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.

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