Question

Leptotene chromosomes have?
A. Two chromatids
B. One chromatid
C. Four chromatids
D. No chromatid

Answer 1

Hint: Also known as leptonema, the leptotene stage is the first of five substages of prophase I in meiosis. The duplicated chromosomes in which each consists of two sister chromatids condense from diffuse chromatin into thin and long strands during the leptotene stage that are more visible within the nucleoplasm. After its chromosomes are duplicated during interphase, a cell destined to become a gamete enters the leptotene stage.

Complete answer:
Option A Two chromatids: The duplicated chromosomes after interphase consist of two sister chromatids. The leptotene stage is the first stage of meiosis prophase \[1\]. In this stage, the chromosomes uncoil and become into thread-like structures. This stage is followed by the zygotene stage.
Hence option A is the correct answer.
Option B One chromatid: The chromosomes divide longitudinally to form a pair of sister chromatids in the leptotene stage. Hence two chromatids are formed at this stage.
So, option B is not correct.
Option C Four chromatid: The pairs of homologous chromosomes come together to form a tetrad or bivalent, which contains four chromatids during the stage of prophase \[1\], in meiosis \[1\]. During prolonged prophase of meiosis \[1\], recombination occurs which is called the leptotene stage, and forms two chromatids.
Hence option C is not correct.
Option D No chromatids: It is observed that, during the leptotene stage, two chromatids are formed.
Hence option D is also not correct.

Hence, Option A) Two chromatids is the correct answer.

Note:
For many years, based upon the appearance of the meiotic chromosomes, the cytologists have divided prophase I into multiple segments, Thus, these scientists have described a leptotene phase, which is then sequentially followed by the zygotene, pachytene, and diplotene phases. Researchers have recently combined cytology and genetics to understand some of the molecular mechanisms that cause the spectacular chromatin rearrangements seen during these periods.