What happens when a section of a chromosome is missing?

When a section of a chromosome is missing, this genetic alteration is referred to as deletion. This occurs when a segment of DNA is lost, either due to errors in DNA replication or as a result of environmental factors or chromosomal breaks. The loss of genetic material can lead to a variety of effects, depending on the size of the deletion and the specific genes that are affected. This may result in developmental abnormalities, genetic disorders, or other physiological issues, as the genes located in the deleted region are not expressed, reducing the organism's ability to produce certain proteins or complete biological functions.

In contrast, inversion refers to a chromosomal alteration where a segment of a chromosome is reversed end to end, without any loss of genetic material. Point mutation involves changes at a single nucleotide in the DNA sequence, which can affect a single gene but doesn't involve large sections of the chromosome. Gene expression is the process through which the information in a gene is used to synthesize proteins, which may or may not be impacted by chromosomal deletions depending on whether the genes involved are deleted or not. Thus, deletion is the term that specifically describes the loss of a chromosomal segment.