Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What type of alleles are usually recessive and may lead to the early death of offspring?

1. Lethal alleles

2. Sex-linked traits

3. Codominant alleles

4. Dominant alleles

The correct answer is: Lethal alleles

Lethal alleles are a specific category of alleles that, when present in a certain combination, can lead to the death of an organism, often before it reaches maturity. These alleles are typically recessive, meaning that an individual must inherit two copies of the lethal allele for the lethal phenotype to manifest. In cases where a lethal allele is present, the usual outcome is that offspring may be unable to survive to reproductive age, leading to early death. Understanding the role of lethal alleles in genetics is crucial when studying inheritance patterns and the implications of certain traits in a population. This knowledge can also help in areas such as breeding programs, where the presence of lethal alleles can impact the viability of offspring. The other options represent different genetic concepts and do not fit the description of alleles that specifically lead to early death among offspring. For instance, sex-linked traits are associated with the X or Y chromosomes and do not inherently lead to lethality. Codominant alleles express both traits simultaneously without resulting in death, and dominant alleles typically require only one copy to be expressed, which is not aligned with the definition of lethal alleles.