Fig. 3. An early prophase spermatocyte nucleus where inter-homolog connections are established in the context of RPA-TN foci prior to SC formation [RPA-TN foci, red; SCYP1 cores and centromeres (cen), FITC, green]. Bivalent #2 has broadly aligned cores with one RPA-TN focus at the site of close alignment prior to SC formation. Other TNs are associated with the unpaired cores (caret). Bivalent #1 has two TNs at the distal, closely aligned cores and an additional RPA-TN interhomolog connection at the inflection (i, asterisk). Bivalent #3 has RPA-TN foci along and at both ends of a long closely aligned segment. Close alignment is extensive in bivalent #4 and SC formation (SC) has been initiated in the distal segment.