A question about jews and their marriage beliefs

[strengththroughsatan89]

I am assuming everyone here knows that strong jewish individuals believe that no jew should marry a gentile or have children with a gentile but only with fellow jews. I know that the reason they do this and even they said the reason to be was to protect their race. So by them saying this it shows that they have concerns with half-breeds being born and than maybe those half-breeds having children with gentiles and so on. Is it possible that after many occurances of this happening that a jew is no longer a jew. I know they will still have the blood of a jew in their veins no matter how little but can their state and way of mind be disrupted by having so many gentile ancestors or will they always be the same. I have been wondering about this lately and since they tell their people not to do this their has to be a reason.