Jack：Hi, Mike. How many toy cars do you have?

Mike：I have four.

Jack：How many toy bears do you have，Amy?

Amy：I have seven.

Jack：Hello, John! How many crayons do you have?

John：I have twelve.

Jack：Do you have toy boats，Sally?

Sally：Yes. I have nine.

Jack：I have sixteen books.

⑴ ____         A.Amy      a.

⑵ ____           B.John       b.

⑶ ____      C.Mike      c.

⑷ ____       D.Jack       d.

⑸ ____    E.Sally       e.

①减数分裂包括两次连续的细胞分裂

②在次级精母细胞中存在同源染色体

③着丝点在第一次分裂后期一分为二

④减数分裂的结果是染色体数减半，DNA数不变

⑤同源染色体分离，导致染色体数目减半

⑥联会后染色体复制，形成四分体

⑦染色体数目减半发生在第二次分裂的末期。