Deletions

Definition

Deletions refer to the loss of a segment of DNA from a chromosome, which can lead to significant genetic consequences. This genetic alteration can disrupt gene function and result in various disorders or phenotypic changes. Depending on the size and location of the deletion, it can have different impacts on an organism's development and function, affecting everything from individual genes to larger chromosomal regions.

5 Must Know Facts For Your Next Test

1. Deletions can occur due to errors during DNA replication or as a result of exposure to certain environmental factors, including radiation and chemicals.
2. They can lead to frameshift mutations if they remove nucleotides that are not in multiples of three, altering the entire downstream protein coding sequence.
3. Deletions are implicated in several genetic disorders, such as Cri du Chat syndrome, which is caused by a deletion on chromosome 5.
4. Some deletions can be benign and may not cause any observable phenotypic effect, while others can be lethal depending on their nature and location.
5. The detection of deletions often requires techniques like fluorescence in situ hybridization (FISH) or comparative genomic hybridization (CGH) for accurate identification.

Review Questions

• How do deletions affect gene expression and what mechanisms might contribute to the phenotypic consequences observed?
  • Deletions can have profound effects on gene expression by removing essential coding sequences or regulatory elements necessary for proper gene function. When a deletion occurs, it may result in the loss of protein production entirely or alter the protein's structure, leading to dysfunctional proteins. Additionally, if the deletion causes a frameshift mutation, it can drastically change how the remaining mRNA is read during translation, further contributing to phenotypic variations.
• Compare and contrast the effects of deletions with those of point mutations in terms of their genetic implications.
  • While both deletions and point mutations can lead to genetic disorders, their implications differ significantly. Deletions often remove larger segments of DNA, which may include multiple genes or regulatory regions, leading to more extensive phenotypic changes. In contrast, point mutations involve a change in a single nucleotide and may only affect one gene product. The consequences of a deletion could be more severe due to the potential loss of multiple functions or regulatory controls compared to a single nucleotide change that might still allow for some level of normal function.
• Evaluate the impact of environmental factors on the occurrence of deletions in human populations and how this might relate to genetic diversity.
  • Environmental factors such as radiation exposure and certain chemicals can increase the likelihood of deletions occurring within human populations by inducing DNA damage during replication. This process contributes to genetic diversity as some individuals may carry these deletions without any deleterious effects while others may experience significant health issues. The presence of such genetic variations due to deletions also plays a role in evolutionary adaptation; populations with diverse genetic backgrounds may better respond to environmental pressures or diseases. Ultimately, understanding these dynamics helps clarify how deletions shape both individual health outcomes and broader population genetics.

Related terms

Chromosomal Aberrations: Structural changes in chromosomes that can include deletions, duplications, inversions, and translocations.

Point Mutation:

A change in a single nucleotide base pair in the DNA sequence, which can lead to different effects compared to larger deletions.

Copy Number Variation (CNV): A phenomenon where sections of the genome are repeated, and the number of repeats can vary between individuals, often including deletions.