Here's a good chance to guess the spelling - if you got the "audio only" or "translate from English" option - by using using the sounds. Given the "sh" sound the S makes, it has to be slender, meaning that it's preceded by a slender vowel. Your choices narrow down from a combination of common spelling of verbs, and the rules that apply to slender and broad vowels. You've seen a couple of different endings to multiple verbs that are all pronounced differently. The S is slender, so there would need to be a slender vowel on either sides of the consonant(s) (slender with slender, broad with broad). Your choices are "i" and "e". I personally have no recollection of seeing "e" used at the left end of a verb, so it's likely "i", and if you remember the "Dua" part of the word, you've just gotta think "Would an 'i' come after 'a'?". As there have been numerous cases in which these two letters accompany each other, that would be a yes. Now for the second slender vowel. I've only ever seen "i" used before "o" in common usage, and this sounds a little like a light "a" sound, if you listen closely. "ea" is really the only choice left, which makes an "a" sound that would be used in "apple" in the English language, so it comes out to "Duaisea" so far. It then sounds like a "na", and, more often than not, what makes a "na" sound, and is preceded by a vowel is "nna". "Duaiseanna" is born at last! Just thought I'd explain in depth. Everyone learns differently. =D
Dr. James Watson auctioned his Nobel Prize medal, so it seems as though he could have chosen to sell it also. Alternatively, perhaps “prizes” refers to ships captured during wartime.
EDIT: “Prizes” in the naval sense would be translated as éadálacha or creacha rather than duaiseanna.
I have to turn off the listening exercises when this comes up, because even my poor spellings of duaiseanna don't register in the system as even a misspelled Irish word. It is very frustrating, because I can't seem to figure out how to spell it no matter how many times I see (I'm now on level 4 of this lesson) and the listening doesn't even allow me to get a hint. It doesn't sound anything like how I expected the sound based on the spelling (sounds douche-e-na vs. looks duway-sina). this, along with the grandparent words, are probably the hardest words to spell I've come across so far. Is anyone else having problems trying to get this word right? Any hints or tips to help me out?
Probably the simplest rule of Irish pronunciation for beginners is that a slender s is pronounced "sh", and a broad s is pronounced "ss". As the s in duaiseanna is slender (the vowels before and after it are the slender vowels í and e), the s in duaiseanna is pronounced "sh", not "ss".
Some of the other words that you've encountered that contain uai are mbuaileann, Luain, nuair, Tuaisceart, uaireadóir and uair, none of which have a "way" sound, so I'm not sure why you think that duaiseanna should sound like "duway-sina".
You might find it helpful to spend some time with the resources listed in the stickied post Irish Pronunciation Guide.