grep (bash) multi-line pattern

Question

In bash (4.3.46(1)) I have some multi-line so called fasta records where each record is initiated by on line with >name and the following lines DNA sequence ([AGCTNacgtn]),

Answer 1

With GNU grep:

grep -Pzo '>chr2\n[AGCTNacgtn\n]+' file | grep .

Output:

>chr2
TTGNACACCC
TGGGGGAGTA