does crossing over necessarily result in recombination of alleles? Explain?

Answer 1

Crossing over happens between 2 sister chromatids. In other words, there would be a new combination of DIFFERENT gene alleles being formed. Traits are still inherited as a whole.

The reason is simple. When crossing-over happens, only one small part of the choromsome would be "exchanged". This slight change would give rise to a unique choromosome. Do note that crossing-over can take place a lot of times during the Diplotene of Prophase I.