Assertion: The complex formed by a pair of synapsed...

Name: Problem 114, Chapter 10: Objective Biology for NEET
Uploaded: 2021-11-15T06:54:29-08:00
Duration: 1 min 9 s
Channel: Parvati Devi
Description: Assertion: The complex formed by a pair of synapsed homologous chromosome is called a bivalent or a tetrad. Reason: The first two stages of prophase I are relatively short lived when compared to the next stage that is pachytene.

Assertion: The complex formed by a pair of synapsed homologous chromosome is called a bivalent or a tetrad. Reason: The first two stages of prophase I are relatively short lived when compared to the next stage that is pachytene.

Key Concepts

Bivalent (Tetrad)

A bivalent, also known as a tetrad, is the structure formed during meiosis when a pair of homologous chromosomes, each composed of two sister chromatids, come together. This organization into four chromatids is crucial for genetic recombination, as it facilitates the crossing over process and ensures proper segregation of chromosomes during the first meiotic division.

Synapsis

Synapsis is the process by which homologous chromosomes pair up closely during early prophase I of meiosis. This intimate pairing enables the precise alignment necessary for crossing over, where segments of genetic material are exchanged between chromatids, thereby contributing to genetic diversity among gametes.

Prophase I

Prophase I is a complex and lengthy phase of meiosis that sets the stage for homologous recombination and proper chromosome segregation. It is subdivided into several substages (leptotene, zygotene, pachytene, diplotene, and diakinesis), each characterized by specific chromosomal behaviors and interactions, and is critical for establishing the conditions required for successful genetic recombination.

Pachytene Stage

The pachytene stage is a key subphase of prophase I during which homologous chromosomes are fully synapsed and genetic recombination is actively taking place. It is during this elongated stage that crossing over occurs, with the formation of chiasmata serving as physical evidence of genetic exchanges, thereby playing a pivotal role in ensuring the genetic variability of the resulting gametes.

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