I have a tomato plant with a huge deformed tomato, and other normal ones.
If I save seeds from the deformed tomato, could it result in plants with more chances of giving deformed tomatos than if I save seeds from normal looking tomatos from the same plant?
Or all tomatos from the same plant share the exact same genetics and doesn't matter which one I save the seeds from?
No, your chance of starting a new variety of tomatoes that bares deformed fruit is slim. Probably the same as your regular tomato making a deformed fruit. Unusual, but not rare.
It does matter the seeds you save. Its matter on which plant donated the pollen to pollinate your plant. It is the same as humans we are all different when we come from different parents. In the case of tomatoes, if it donated it's own pollen or the same variety plant donated the pollen then you will get the same type of tomato as your plant. If it was pollinated by a different variety, what you get will be unique. You will be the only person growing that plant. If it self-pollinated, it had not different genetics to work with, so it basically creates a clone of itself.
Radboud University in the Netherlands has an interesting publication on tomato pollination and how things can go wrong. The picture in the article shows how the male and female parts are very closely aligned, and if they become productive at the same time, all it takes is a shake from wind or air blower or visiting insect to successfully transfer pollen from the male to female parts, at which point fertlization happens and further pollination is ineffective. Tomatoes are self fertile, so there is no need for cross pollination and the genetics remain stable.
However in the case that the male parts do not produce as necessary it is possible for visiting insects bearing pollen from other tomato plants to fertilize the flower leading to potentially substantially differing genetics. The effect of fertilization on the morphology of the fruit is undetermined, so best to be safe than sorry.
