The old MBR 512 bytes partition table is no longer valid if you are using GPT.
To copy a GPT table with dd to another disk do it like so:
Below sda is the source disk and destination disk is sdb (change to meet your needs).
dd if=/dev/sda of=/dev/sdb bs=1536 count=1
You can also use dd to backup your partition table like normal but with the bs of 1536