Advanced Placement (AP) Biology Practice Exam

Which term describes chromosomes that carry the same genes but may have different alleles?

1. Sister chromatids

2. Homologous chromosomes

3. Diploid chromosomes

4. Haploid chromosomes

The correct answer is: Homologous chromosomes

The term that describes chromosomes carrying the same genes but with potentially different alleles is homologous chromosomes. These are pairs of chromosomes, one inherited from each parent, that have the same structure and gene sequence but can differ in the specific version of a gene, known as an allele. This variation is crucial for genetic diversity, allowing for different traits to emerge in an organism. Sister chromatids refer to the identical copies of a chromosome that are formed when a chromosome replicates. They are exact duplicates and therefore do not differ in allelic content. Diploid chromosomes pertain to the number of chromosome sets in a cell, indicating that there are two sets of chromosomes (one from each parent) but do not specifically refer to allelic differences. Haploid chromosomes indicate a single set of chromosomes, which is typically found in gametes (sperm and eggs). These cells contain only one allele for each gene, making it impossible to have different alleles for the genes in this context. Homologous chromosomes are essential for processes like meiosis, where their pairing allows for genetic recombination, further contributing to genetic diversity in sexually reproducing organisms.