Biological Systems MCAT Practice Exam

Diploid germ cells undergo a specialized type of cell division known as meiosis to become haploid gametes. Meiosis consists of two rounds of division (meiosis I and meiosis II) and results in the reduction of the chromosome number by half. This is critical for sexual reproduction, as it ensures that when gametes fuse during fertilization, the resulting zygote will have the correct diploid number of chromosomes. In meiosis, the diploid germ cells first undergo replication, followed by two rounds of division which separate homologous chromosomes in the first division and sister chromatids in the second division. This process not only reduces the chromosome number but also introduces genetic diversity through recombination and independent assortment. The culmination of meiosis is the formation of four haploid cells that can develop into gametes, such as sperm and eggs. Other processes mentioned, such as fertilization and mitosis, do not involve the reduction of chromosome number from diploid to haploid. Fertilization combines two haploid gametes to form a diploid zygote, while mitosis is a process of cell division that results in two genetically identical diploid daughter cells without a change in chromosome number. Mutation refers to changes in the DNA sequence but is not