This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Meiosis Prophase 1 : Leptotene”.
1. Meiosis is called reduction division.
Explanation: In meiosis there is a reduction in chromosome number to half that is present in normal cell. Thus, meiosis is called reduction division.
2. In haploid organism meiosis takes place in _____________
a) Somatic cell
Explanation: In haploid organisms the zygote is diploid which undergoes meiosis to give a haploid individual. Here, egg and other gamete are haploid as is somatic cell, so no meiosis is required by it.
3. The reduction division of mitosis is _________________
a) The 1st division
b) The 2nd division
c) The G2 phase
d) The telophase
Explanation: In the 1st division the chromosome number is reduced to half as the homologous pair separates to opposite pole. On the other hand in 2nd division the number of chromosome is constant just the chromatids separate like normal mitosis.
4. Which of the following is true for pre-leptotene phase?
a) Chromosome compaction
b) Pairing of homologous
c) Marked increase in nuclear volume
d) Disappearance of nuclear membrane
Explanation: There is a marked increase in nuclear volume in pre-leptotene. Then the chromosomes are thin and randomly disperses, it is the preparatory stage for a cell to enter meiosis.
5. The leptotene Bouquet stage is seen in ______________
Explanation: In animals and especially in insects in leptotene stage the chromosomes have their ends drawn to a point forming a bouquet structure. This is near the centriol. As plants lack centriol it is not seen in plants.
6. Lillium, a plant, will lack bouquet structure in letotene.
Explanation: Lillium is an exceptional case among plants where it has a Bouquet like an arrangement of the chromosomes as seen in animals.
7. Which of the following is not true for leptotene phase?
a) It is a short phase
b) Chromosomes have beads on a string appearance
c) Longitudinal double nature of chromosome starts to appear
d) Bouquet like structure is formed
Explanation: In leptotene phase the chromosomes have bead on string appearance with the chromatin fiber arranged like lateral loops on axis. But the bivalent nature is not yet visible at that time.
8. During leptotene there are ___________polyribosomes and ___________ ER vesicles in cytoplasm.
a) Few, many
b) Many, few
c) Few, Few
d) Many, Many
Explanation: During the leptotene phase as the polyribosomes are synthesized, there are many polyribosomes ready for transcription. But there are only a few ER vesicles.
9. Choose the wrong statement out.
a) The leptotene chromosomes are arranged around an axis
b) The chromosomes form loops
c) The unbranched loops are lateral
d) Lateral filaments composed of two independent protein fibrils, one for each chromatid.
Explanation: The chromosomal loops are often branches in lateral disposition. While it is true that they are arranged in loops around the axis and have protein fibrils.
10. Which of the following is directly correlated to polyribosomal synthesis in leptotene stage?
a) RNA synthesis
b) Protein synthesis
c) Protein turnover
d) Protein function
Explanation: The rate of protein production and its turnover rate may be related to polyribosomes but the function of a protein is specific to the protein itself. Protein function is not directly affected.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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