Dicot leaf (dorsiventral leaf) 

Epidermis ;

The upper and  lower surfaces are covered by the epidermis.

Cells of epidermis are  Parenchymatous.

Stomata restricted to lower surface (HYPOSTOMATIC) 

Outer walls thickened and cutinized.

Mesophyll ;

Palisade (upper)

Spongy (lower)

Vascular tissue ;

Conjoint, Collateral and Closed surrounded by Bundle sheath

Xylem (Adaxial) and Phloem (Abaxial)

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Cohesins are composed of four subunits: 

Smc1, Smc3, Scc1, and Scc3

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Smc1 and Smc3 are members of the structural

maintenance of chromosomes (SMC) protein family, characterized by globular domains at the N- & C-termini connected by a long α helix, bind and hydrolyze ATP.

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The ATPase domains interact with the proteins

Scc1 and Scc3, which together form a cohesin ring structure which embrace one or both copies of the replicated DNA.

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Cohesin-mediated cohesion between sister chromatids is established by a two-step process:

1.Loading and unloading of cohesins

2. Stabilization of cohesins

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During G1, 

cohesins associate with chromosomes by cohesin loading factors Scc2 and Scc4 and unloaded continuously by a cohesin associated complex Pds5 and Wap1 proteins. 

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During S phase

DNA-bound G1 cohesins Convert into cohesive complexes by cohesin acetyl transferases (CoATs)

which acetylate Smc3 subunit & prevents unloading of cohesins by Pds5-Wapl, thereby stabilizing the cohesins on chromosomes.