Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

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Study for the Biology STAAR Test. Improve your skills with flashcards and multiple choice questions, each question is accompanied by hints and explanations. Prepare for success!

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What does it mean if an organism is heterozygous?

It has the same alleles
It has two different alleles
It is a purebred organism
It has no dominant traits

The correct answer is: It has two different alleles

A heterozygous organism possesses two different alleles for a particular gene. This genetic variation means that for a given trait, one allele may be inherited from one parent and a different allele from the other parent. For example, in the case of flower color, a heterozygous plant might have one allele for red petals and another for white petals. This condition allows for genetic diversity, which can influence traits and their expression in the organism. In contrast, a homozygous organism would have identical alleles for a particular gene, which is not the case for a heterozygous individual. Consequently, being heterozygous often results in a mix of dominant and recessive traits being expressed, which can lead to a phenotype that displays a dominant trait when paired with a recessive allele.