BlackRock U.S. Mortgage Fund Institutional is an open‑end mutual fund focused on securitized fixed income, designed to deliver high total return by investing primarily in mortgage‑backed and other mortgage‑related securities. According to its stated approach, the portfolio allocates at least a substantial majority of assets to securities issued or guaranteed by U.S. government agencies and instrumentalities, complemented by positions across the broader U.S. mortgage market to capture income and structural opportunities. The fund emphasizes agency mortgage pools, Uniform Mortgage‑Backed Securities, and related instruments across maturities, while maintaining institutional features such as a low distribution fee level and a sizable minimum initial investment. It distributes income monthly, reflecting the cash flow profile of underlying mortgage assets. Within the bond landscape, it sits in the multisector or securitized income segment, offering targeted exposure to U.S. residential mortgage credit and prepayment dynamics with an intermediate effective duration profile. The strategy aims to serve institutions seeking diversified mortgage exposure and a dedicated sleeve within fixed income allocations, supported by BlackRock’s securitized research and trading platform.