Under the constitution of 10 July 1973, the Bahamas adheres to a republican form of government, formally headed by the British sovereign, who is represented by a governor-general. Executive authority is vested in a prime minister and a cabinet. The bicameral legislature consists of a 16-member Senate, appointed by the governor-general (nine on the advice of the prime minister, four on the advice of the opposition leader, and three at the governor's discretion), and an elected 40-member House of Assembly. The prime minister is the leader of the majority party in the House. The normal span of the elected legislature is five years, but, as in the United Kingdom, elections can be called at any time. Suffrage is universal at age 18.