Bivalent (genetics)

In most organisms, each replicated chromosome (composed of two identical sisters chromatid) elicits formation of DNA double-strand breaks during the leptotene phase.

In most organisms, each replicated chromosome (composed of two identical sister chromatids[1][2]) elicits formation of DNA double-strand breaks during the leptotene phase.

During the initial stages of organismal development, the coordinated activation of diverse transcriptional programs is crucial and must be carefully executed to shape every organ and tissue.

Bivalent which promoters and poised enhancers are regulatory regions decorated with histone marks that are associated with both positive and negative transcriptional outcomes.

The packed gives information for regulation nucleosome of physical barrier they show impact on the chromatin remodelers parts N- terminal parts of histone particle, histone tails, covalent post-translational modifies and also creates an epigenetics of [PCG] and [TRXG] plays an initial role these mutations caused in groups from transformation in Drosophila shows a clearcut information A bivalent is the association of two replicated homologous chromosomes having exchanged DNA strand in at least one site called chiasmata.

With the availability of single-cell RNA sequencing (scRNA-seq) data, subsequent switches in transcriptional state at bivalent promoters can be studied more closely.

At the meiotic metaphase I, the cytoskeleton puts the bivalents under tension by pulling each homolog in opposite direction (contrary to mitotic division where the forces are exerted on each chromatid).

This tension results in the alignment of the bivalent at the center of the cell, the chiasmata and the distal cohesion of the sister chromatids being the anchor point sustaining the force exerted on the whole structure.

Keywords: Bimodality; Bivalency; Chromatin state; Embryonic stem cells; Genome regulatory network; Hidden Markov model; Pseudo time; scRNA-seq.