When veiwing a human karyotype to detect genetic disorders, whic situation indicate a genetic problem

There are two scenarios where viewing a karyotype one can detect a genetic disorder.

#1 : When a pair of chromosomes has 3 chromatids

#2 When a pair of chromosomes has 1 chromatids

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.