Does this mysqldump command lock all tables?

When I execute the command below, does mysqldump lock all tables while the backup is in process? I want to make sure this is the appropriate type of backup command for MyISAM database.

mysqldump -h myhostname --default-character-set=utf8 -u root --password=mypassword --opt --single-transaction DBname > /root/backup.sql

OT, but you’re a Genesis fan?

Near the beginning of it says that --opt includes --add locks.