Final answer:
The true statements about duplications are that they may offer evolutionary advantages by forming new genes and can result from unequal crossing-over, making 'd. Two of the above.' the correct answer. Duplications provide genetic material for evolutionary changes, allowing duplicated genes to evolve new functions while retaining the original gene's function.
Step-by-step explanation:
Among the given statements about duplications, the true one is that they may have a long-term evolutionary advantage in leading to the formation of new genes and that they may result from unequal crossing-over. Thus, the correct answer is 'd. Two of the above.'
Duplications occur when a segment of DNA is repeated, leading to multiple copies of genes in the chromosome. While it's a common perception that genetic mutations such as duplications and deletions are harmful, the reality is more nuanced. For example, duplications can sometimes be beneficial in an evolutionary context because they provide an extra copy of a gene, allowing one copy to maintain its original function while the other is free to evolve new functions.
Duplications can arise during DNA replication, particularly during the S phase of either mitosis or meiosis, or due to errors not corrected during prophase I of meiosis. Additionally, these genetic changes can result in variability that is key to species evolution. When considering the immediate impact on an organism, duplications can be less harmful than deletions because the organism retains the gene function despite the duplication, whereas deletions can lead to a complete loss of gene function.