Deletion

Definition

Deletion refers to a type of mutation where a segment of DNA is lost or removed from a chromosome. This can result in significant changes to gene function and expression, leading to inherited disorders or diseases. Deletions can occur in various sizes, from a single nucleotide to larger sections of the chromosome, impacting the organism's phenotype and potentially disrupting normal biological processes.

5 Must Know Facts For Your Next Test

1. Deletions can lead to frameshift mutations if they remove nucleotides that are not in multiples of three, altering the entire downstream amino acid sequence.
2. Certain genetic disorders, such as Cri du Chat syndrome, are caused specifically by large deletions in chromosome 5, leading to developmental issues.
3. Small deletions can also contribute to cancers by removing tumor suppressor genes or creating fusion genes that drive uncontrolled cell growth.
4. The likelihood of deletion events can increase due to environmental factors such as radiation, which can damage DNA integrity.
5. DNA repair mechanisms exist to fix deletions, but failure in these systems can result in permanent changes that are passed on during cell division.

Review Questions

• How does a deletion mutation affect gene expression and protein synthesis?
  • A deletion mutation can significantly disrupt gene expression and protein synthesis by removing critical portions of the DNA sequence. If the deletion is not a multiple of three nucleotides, it causes a frameshift mutation, altering the reading frame for codons and resulting in a completely different amino acid sequence downstream. This can lead to nonfunctional proteins or truncated proteins that cannot perform their intended roles, which may contribute to diseases or genetic disorders.
• Discuss how deletions can contribute to inherited disorders and give examples of specific conditions caused by deletions.
  • Deletions can lead to inherited disorders by removing essential genes or regulatory elements necessary for normal development and function. For example, Cri du Chat syndrome results from a deletion on chromosome 5, which causes developmental delays and characteristic physical features. Another example is Duchenne muscular dystrophy, where deletions in the dystrophin gene disrupt muscle function, leading to severe muscle degeneration over time.
• Evaluate the implications of deletion mutations on cancer development and progression.
  • Deletion mutations play a crucial role in cancer development by disrupting genes that regulate cell growth and division. For instance, deletions of tumor suppressor genes can remove the body's natural checks on cell proliferation, allowing for unchecked growth. Furthermore, certain deletions may lead to fusion genes that promote oncogenesis. Understanding these mechanisms is vital for developing targeted therapies and improving treatment outcomes for patients with cancers driven by specific genetic alterations.

Related terms

Mutation: A permanent alteration in the DNA sequence that makes up a gene, which can affect how that gene functions.

Chromosome: A thread-like structure made of DNA and proteins that carries genetic information; humans typically have 23 pairs of chromosomes.

Gene Expression: The process by which the information encoded in a gene is used to produce a functional product, often a protein, which contributes to the organism's traits.