Final answer:
If a deletion mutation occurs in a homozygote, it can have lethal effects or cause significant disruption in gene functions, leading to diseases like cystic fibrosis. The impact is more severe as there is no normal copy left to perform the gene's normal function. Frameshift mutations can also arise, altering or terminating protein synthesis.
Step-by-step explanation:
If a deletion mutation occurs in a homozygote, it could have a range of effects depending on the location and size of the deletion. If the deletion occurs within a gene that is vital to the organism, and both copies of the gene are affected (since the individual is homozygous), the results could be lethal or cause a significant disruption in the normal functions of that gene.
Conditions like cystic fibrosis can result from deletion mutations that remove important coding information. In cases where the deletion affects non-essential genes or areas of the DNA that do not significantly alter protein function, the organism might not display any observable consequences.
Additionally, since a homozygote has two identical copies of a gene, a deletion in both would mean there is no normal copy to carry out the gene's function, which could be more severe than in a heterozygote that might have one unaffected gene copy left.
As an example, the Curly allele in Drosophila, which is lethal when homozygous, would lead to death before birth if a deletion mutation removed the normal function of both gene copies.
In other scenarios, like in the presence of a dominant lethal allele, such as the one causing Huntington disease, the symptoms might not arise until adulthood, but the mutation would eventually be fatal.
Deletion mutations can also lead to frameshift mutations, causing a shift in the reading frame of the DNA and potentially altering the entire protein product, making it nonfunctional or lead to early termination of protein synthesis.