The nameservers for the domain will remain the same during the transfer. So, if you are hosting the DNS for the domain on your own or with a webhosting company, they will be transferred over and there shouldn't be any downtime for the domain.

If you use your registrar's default nameservers and want to avoid downtime during transfer, we advise you to do the following:

• set your domain to use our DNS as back up nameservers;
• once your domain starts using our DNS you can initiate a transfer;