Examkin

Soru

Zorluk: Çok zorCell Biology, Genetics, and Evolution

Arrange the following cellular events occurring during Prophase I of Meiosis I in the correct chronological order from beginning to end:

  1. 1Condensation of chromatin threads into distinct, long, thin visible chromosomes while attached to the nuclear membrane.
  2. 2Formation of the synaptonemal complex facilitating the precise pairing of homologous chromosomes (synapsis).
  3. 3Exchange of genetic material between non-sister chromatids of homologous chromosomes mediated by recombination nodules.
  4. 4Dissolution of the synaptonemal complex resulting in homologous chromosomes moving slightly apart while remaining held together at chiasmata.
  5. 5Complete terminalisation of chiasmata accompanied by the breakdown of the nuclear envelope and disappearance of the nucleolus.

Cevap

The correct chronological order of events during meiotic Prophase I is: (1) Chromatin condensation (Leptotene), (2) Synaptonemal complex formation and pairing (Zygotene), (3) Recombination nodules and crossing over (Pachytene), (4) Dissolution of synaptonemal complex and visible chiasmata (Diplotene), and (5) Terminalisation of chiasmata and nuclear envelope breakdown (Diakinesis).
Prophase I of meiosis consists of five sequential stages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis. Chromatin condensation initiates in Leptotene, followed by homologous pairing and synaptonemal complex formation in Zygotene. Recombination modules catalyze crossing over in Pachytene. Dissolution of the synaptonemal complex in Diplotene reveals chiasmata, which then undergo terminalisation alongside nuclear membrane breakdown in Diakinesis.

Adım Adım Çözüm

1
Identify the first substage of Prophase I (Leptotene).
Chromatin condenses into long thread-like structures visible under light microscopy.
Compaction of genetic material is the prerequisite step before homologous chromosome pairing can take place.
2
Identify the second substage of Prophase I (Zygotene).
Homologous chromosomes align side-by-side (synapsis) mediated by the zipper-like synaptonemal complex.
Stabilizing pair structure is required to position non-sister chromatids in close proximity for recombination.
3
Identify the third substage of Prophase I (Pachytene).
Recombination nodules form and non-sister chromatids undergo enzymatic reciprocal crossing over.
Genetic variation is introduced through physical exchange of DNA segments between paired homologues.
4
Identify the fourth substage of Prophase I (Diplotene).
The synaptonemal complex degrades, causing homologues to separate except at points of crossing over (chiasmata).
Desynapsis allows structural visualization of the X-shaped chiasmata locations.
5
Identify the fifth substage of Prophase I (Diakinesis).
Chiasmata shift toward the ends of chromosomes (terminalisation), the nucleolus degrades, and the nuclear envelope disintegrates.
Prepares the bivalent chromosomes for alignment along the metaphase plate in Meiosis I.

Anahtar Kavram

Substages and Molecular Events of Meiotic Prophase I
Bu soruyu puanla

Konular

Cell Biology, Genetics, and Evolution

Bu konudan daha fazla soru