Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What characterizes normal sexual reproduction?

1. Offspring receive all chromosomes from one parent

2. Offspring receive half of their chromosomes from each parent

3. Offspring are clones of one parent

4. Offspring develop from a single cell division

The correct answer is: Offspring receive half of their chromosomes from each parent

Normal sexual reproduction is characterized by the process through which offspring are produced by combining genetic material from two different parents. In this process, offspring receive half of their chromosomes from one parent and half from the other, leading to a unique genetic makeup. This mixing of genetic material results in greater genetic diversity within a population, which is important for evolution and adaptation. The process begins with the formation of gametes (sperm and eggs) through meiosis, where the chromosome number is halved. When these gametes fuse during fertilization, they create a zygote with a complete set of chromosomes, restoring the full number. This genetic mixing is crucial because it allows for variations that can enhance survival in changing environments. In contrast, offspring that receive all chromosomes from one parent or are clones are produced through asexual reproduction, which does not involve the combination of genetic material from two different sources. Additionally, offspring that develop from a single cell division do not reflect the complexity and genetic variability that characterize sexual reproduction. Thus, the key feature of sexual reproduction lies in the contribution of genetic material from both parents, leading to offspring that are genetically distinct from either parent.