Unreachability of ${\mathbf{\Gamma }}_{\mathbf{2}\mathbf{n}+\mathbf{1},\mathbf{m}}$

We find bounds for the maximal length of a sequence of distinct ${\mathbf{\Gamma }}_{\mathbf{2}\mathbf{n}+\mathbf{1},\mathbf{m}}$-sets under $AD$ and show there is no sequence of distinct ${\mathbf{\Gamma }}_{\mathbf{2}\mathbf{n}+\mathbf{1}}$-sets of length ${\mathbf{\delta }}_{\mathbf{2}\mathbf{n}+\mathbf{3}}^{\mathbf{1}}$. As a special case, there is no sequence of distinct ${\mathbf{\Gamma }}_{\mathbf{1},\mathbf{m}}$-sets of length ${\mathrm{\aleph }}_{m+2}$. These are the optimal results for the pointclasses ${\mathbf{\Gamma }}_{\mathbf{2}\mathbf{n}+\mathbf{1}}$ and ${\mathbf{\Gamma }}_{\mathbf{1},\mathbf{m}}$.