Final answer:
The correct statements about a tetrad are that it consists of four chromatids, and two chromosomes, is formed in zygotene and visible in pachytene, and results from the formation of the synaptonemal complex. The correct answer is that statements 1, 2, 5, and 6 are true.
Step-by-step explanation:
When considering which statements about a tetrad are true, we must look at the structure and behavior of chromosomes during meiosis. A tetrad consists of four chromatids, which correspond to two homologous chromosomes, each with two sister chromatids. Tetrads are indeed formed during the zygotene stage of prophase I through the formation of the synaptonemal complex, and they become clearly visible during the pachytene stage. Each chromosome has a centromere, but since there are two chromosomes involved in a tetrad, that would equate to only two centromeres, not four. Additionally, each chromosome has a kinetochore structure, but since a tetrad consists of two homologous chromosomes, altogether there would be two kinetochores, one for each chromosome. The separation of sister chromatids occurs during anaphase II of meiosis, not prophase I. Therefore, the correct answer would be B) 1,2,5,6 are correct as they accurately describe a tetrad.