Cialis redirects here. For the Central Asian kingdom, see Karasahr. Tadalafil (INN) is a PDE5 inhibitor marketed in pill form for treating erectile dysfunction (ED) under the name Cialis see-AL-iss, and under the name Adcirca ad-SUR-kuh for the treatment of pulmonary arterial hypertension.
Quick Answer. The synapsis process occurs in the prophase I stage of meiosis. In synapsis, replicated homologous chromosomes link, which become known as a tetrad. Crossover between two pairs of tetrads can occur at any time. Continue Reading.
Further genetic variation comes from crossing over, which may occur during prophase I of meiosis. In prophase I of meiosis, the replicated homologous pair of chromosomes comes together in the process called synapsis, and sections of the chromosomes are exchanged. You can see that after crossing over, the resultant chromosomes are neither entirely maternal nor entirely paternal, but contain genes from both parents. Synapsis and crossing over occur only in meiosis.