Diakinesis - Process and Stages

Our cell division process has different stages. There are five stages that make up the Prophase stage 1 of meiosis. They are Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis. Diakinesis is the last stage of meiosis, characterised by chiasmata terminalisation.

Table of Contents:

What is Diakinesis?
What is Meiosis?
Stages of Prophase I
Diakinesis
Stages of Diakinesis
Practice Problems
Frequently Asked Questions

What is Diakinesis?

Diakinesis is the final stage of prophase 1. In this stage, the chromosomes condense and nucleolus fragments and envelopes disappear. After these stages, the cell division enters the next phase, which is metaphase. During this Diakinesis, the nuclear membrane breaks down. Chiasmata Terminalization is a characteristic in which chiasma moves to the end and chromatids attach only to the terminal chiasmata.

What is Meiosis?

Meiosis is a form of cell division that takes place in germ cells. This gives rise to genetically diverse cells or gametes. Meiosis takes place while producing gametes like egg and sperm cells. There are two stages of Meiosis: meiosis I and meiosis II. Each stage has different phases. Meiosis I comprises four stages: prophase I, metaphase I, anaphase I, and telophase I. The first stage of Meiosis I, the prophase I, has substages which include leptotene, zygotene, pachytene, diplotene and diakinesis.

Stages of Prophase I

Leptotene

Leptotene is the first stage of Prophase. It involves condensing the replicated chromosomes. It continues throughout the process of prophase. During this process, the chromosomes look like beads of a necklace, in which the beads are called chromomeres. The sister chromatids are closer to each other and connect to the nuclear envelope. It is a short stage.

Zygotene

Zygotene is the second stage of Prophase. It starts the connections between the homologous chromosomes. It is also known as synaptonemal complexes due to the coils of chromatin. It allows many points of interaction by forming up and down the chromosomes. They are held together by synaptonemal complexes.

Pachytene

Pachytene is the third stage of Prophase. It is the process of crossing over to ensure the recombination of genetic information from parental DNA sequences. It takes place once the tetrad is developed. The chromosomes are linked as pairs; however, the chromatid sisters start to split from each other.

Diplotene

Diplotene is the next stage, in which the chromosome pairs start to disconnect due to the degradation of synaptonemal complexes. However, they don’t move far away as they are still connected by the chiasmata. Their repulsive properties cause an initial movement.

Diakinesis

Diakinesis is the last stage of the Prophase of meiosis cell division. The word “ Diakinesis” refers to “moving through”. During this stage, the chromosomes condense, and the four tetrad components become apparent. The crossing over sites gets intertwined with an efficient overlapping which results in Chiasmata.

These Chiasmata are the connections that are located at the ends of chromatid arms of chromosomes. It refers to the termination of chiasmata. The chromosomes can not migrate to the ends of the unfinished spindle as they are highly condensed and joined by chiasmata. The nuclear envelope disintegrates into vesicles, and the nucleolus disappears. The four chromatids and the chiasmata are clearly visible now. The spindle remnants can move along with centrioles for spindle formation.

Now the Meiotic spindle fibres get started with the formation of the next stage of meiosis I, metaphase I.

Stages of Diakinesis

In diakinesis, the chromosomes are in their robust state. In a bivalent, there is at least one chiasm connecting the homologous chromosomes. Thus it results in moving centrosomes to the equator. The nucleolus disappears, the nuclear envelope collapses, and the mitotic spindles move. It is a transitional phase to metaphase. The following are the changes happening during Diakinesis:

A complete vanishing of the nucleolus.
Loss of nuclear membrane.
Chiasmata move to the ends of chromosomes as homologous chromosomes and start to break.
Formation of Spindle apparatus at the end.
Recondense of chromosomes, transcription stops and transitions to metaphase.

Practice Problems

Q1. Which of the following involves the formation of spindle apparatus?

A. Diakinesis
B. Pachytene
C. Diplotene
D. Zygotene

Answer: A. Diakinesis

Explanation: The Meiotic spindle fibres get started with the formation of the next stage of meiosis I, metaphase I. Thus the formation of the spindle apparatus at the end of Diakinesis.

Q2. Which of the following disappear during Diakinesis?

A. Nucleus
B. Chromosomes
C. Spindle fibres
D. Nucleolus

Answer: D. Nucleolus

Explanation: During Diakinesis, the nuclear envelope disintegrates into vesicles and the nucleolus disappears.

Q3. Pick the odd one out.

A. Diakinesis
B. Pachytene
C. Diplotene
D. None of the above

Answer: D. None of the above

Frequently Asked Questions

Q1. Why is Diakinesis best observed in flower buds?
Answer: Diakinesis is the substage of meiosis. Meiosis is a process of cell division in reproductive organs. In flowering plants, the reproductive organs such as the stamens, pistils, anthers and ovules are present. Thus, Diakinesis can be observed clearly in flower buds.

Q2. In which part of the plant is meiosis observed?
Answer: Meiosis can be found in the sporangia in plants. Microsporangium is the best-suited portion of the plant for meiosis research.

Q3. What are the stages of Meiosis?
Answer: Meiosis involves the following stages: