Final answer:
Nucleotide-repeat sequences are the short repeated sequences that can cause unequal crossing over, leading to genetic variations such as duplications and, in more severe cases, translocations.
Step-by-step explanation:
The type of short repeated sequences that cause unequal crossing over are called nucleotide-repeat sequences. These sequences often lead to genetic variations such as duplications when they misalign during the recombination process of meiosis. Unequal crossing over can occur when homologous chromosomes align imperfectly during prophase I due to the presence of similar repetitive sequences at different loci, leading to duplications in one chromosome and deletions in the other. Duplications can contribute to genetic diversity if they are retained and do not significantly alter the phenotype of the organism. However, some duplications, especially those that involve nonhomologous chromosomes (translocations), can be lethal or cause significant phenotypic changes.