Final answer:
During metaphase I of meiosis in humans, there are 23 tetrads present, each consisting of a pair of homologous chromosomes. This stage is crucial for genetic diversity due to the random arrangement of tetrads and independent assortment. Option a is the correct answer.
Step-by-step explanation:
In humans, during metaphase I of meiosis, there are 23 tetrads present. Each tetrad consists of a pair of homologous chromosomes, one inherited from each parent, for a total of 46 chromosomes. At this stage, tetrads align at the metaphase plate, which is the midpoint between the two poles of the cell.
The random arrangement and orientation of these tetrads is essential for genetic diversity, as it allows an equal chance for microtubule fibers to contact either a maternally or paternally inherited chromosome, and each tetrad's orientation is independent of the others.
This contributes to over eight million possible combinations due to the independent assortment of chromosomes coupled with crossing over events that occur prior in prophase I.
The correct option in the final answer to the question 'In humans, how many tetrads are present in metaphase I of meiosis?' is a) 23.