A project I am working on and off is compiling lexical parallels that have been proposed in connection to various proposed external relationships of Uralic. Occasionally this kind of work turns up nice new etymological insights.
One of the best-retained — and also one of the more specific — verbs of motion reconstructible for Proto-Uralic is *kälä- ‘to wade’: reflected in e.g. Northern Sami gállit ‘to wade’, Finnish kahlata ‘to wade’ (an old loan from Samic), and Hungarian kel ‘to rise’. (The meaning ‘to rise’ is found also in Mansi and Khanty; the latter also has ‘to step up on land’.) This has been compared with the Yukaghir verb *kel- ‘to come’. The pairing is phonetically OK, but semantically it does not seem impressive. It might be acceptable if a relationship between Uralic and Yukaghir were already established, but it offers hardly any evidence for a relationship in the first place.
Interestingly enough, the same Uralic verb has also been compared with Turkic *gel- ‘to come’ — with the exact same semantics and an equally compatible phonetic shape! (E.g. already Björn Collinder in Fenno-Ugric Vocabulary, 1955/1977, reports both comparisons.) Probably the first step here should be to analyze the Yukaghir word as a loan from Siberian Turkic, and worry about any possible Uralic relationships later.
I would predict that pitting the Uralo-Yukaghir and Ural-Altaic hypotheses against each other may turn up further cases like this where a straightforward loan etymology is available. It’s already been noted by Rédei in his “Zu den uralisch-jukagirischen Sprachkontakten” (1999, in FUF 55) that many of the Uralic-Yukaghir lexical parallels extend to some of the “Altaic” languages as well…
Freelance reconstruction 
“Come” > “come out” > “come out of the water” = “step up on land” > “wade”?
Or maybe ‘step up’ > ‘step in’ > ‘enter’ > ‘come’; ‘step up’ > ‘step out of water’ > ‘wade’. Alas, a plausible explanation is not necessarily yet a particularly probable one.
Does Yukaghir have converb constructions? I am presently unfamiliar with this language. Considering the myriad of converb constructions in Turkic that feature *kel- (what is your motivation for reconstructing the Proto-Turkic with a voiced velar?), it might be fruitful to see if Yukaghir has calqued any and if that may have served as a route for borrowing of the verb.
I am not too delved into the details of Yukaghir grammar either. I have not run into mention of any, but I cannot confirm that it doesn’t have any, either…
The reconstruction *gel- I’ve grabbed from Anna Dybo & Oleg Mudrak’s online Proto-Turkic database (as a part of the Tower of Babel project). I can see that the voiced /g/ appears to be limited to Oghuz, though, and I would not be surprized if the DB had problems similar to e.g. its Uralic counterpart.
Since it is part of a dubious macrofamily reconstruction, that database features Proto-Turkic reconstructions very different from the general consensus, so best to avoid citing proto-forms form there. As I mentioned in a comment a few months ago, the Грамматика тюрских языков series remains a good reference (except for the last volume, where Dybo took over the project).
I think I found out what’s going on. Dybo in EDAL, page 137:
“Thus, the reconstruction is almost completely traditional, with only the following modifications:
1. The distinction of initial voiced/voiceless consonants is primarily based on Oghuz evidence, as was already shown in Иллич-Свитыч 1963, 1965, accepted in EDT and additionally elaborated in АПиПЯЯ 6-10, Дыбо 1991 and РР 70-85. We should mention that the distinction of *g- vs. *k- is reliably reconstructed only before front vowels; before back vowels we can only reconstruct a “hyperphoneme” *K-.”
In other words, as far as I can tell, Dybo saw the choice of either assuming an unconditioned split in Oghuz or projecting the Oghuz distinction all the way back to Proto-Turkic and assuming mergers in the other branches (whatever “primarily” ends up meaning). Well, I wouldn’t be surprised to learn that it’s actually a conditioned split… (For non-initial PA *k, p. 69 already claims that it normally became PT *k, but became PT *g instead if the next PT consonant was *r.)
The note about */k/ and */g/ being distinguished only before front vowels is repeated at every opportunity in the section on Altaic sound correspondences (pp. 67–73). It’s not explicitly stated whether it’s supposed to continue a PA distinction or not.
No, that’s not why. The database also features Pokorny’s hopelessly outdated PIE reconstructions (next to no laryngeals, next to no consideration of Anatolian or Tocharian, underrepresentation of Albanian etc. etc.), simply because Pokorny authored the last all-encompassing PIE dictionary – digitizing that was easier than the more intellectually honest way of compiling the database from dozens of smaller, more recent sources.
Pokorny, BTW, consistently erred on the side of inclusion, putting everything in his dictionary that might conceivably go back to PIE even if irregular developments would need to be assumed; that’s why the Moscow School keeps doing the same. They also keep treating PIE laryngeals as an afterthought.
Oops. I really shouldn’t have cut off the quote before “very different from the general consensus”. :p