Aspects of this topic are discussed in the following places at Britannica.
Chromosome breaks often heal spontaneously, but a break that fails to heal may cause the loss of an essential part of the gene complement; this loss of genetic material is called gene deletion. A germ cell thus affected may be capable of taking part in the fertilization process, but the resulting zygote may be incapable of full development and may therefore die in an embryonic state.
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