Deletions

Definition

Deletions refer to the loss of a segment of DNA from a chromosome, which can result in significant genetic alterations. This genetic change can impact gene function, leading to a variety of consequences, particularly in the context of tumor suppressors and proto-oncogenes. When deletions occur within critical genes, they can disrupt normal cell regulation and promote cancer development.

5 Must Know Facts For Your Next Test

1. Deletions can lead to the complete loss of gene function if they remove essential coding regions or regulatory elements from a gene.
2. In tumor suppressor genes, deletions can result in the inability to regulate cell division, increasing the risk of uncontrolled cell growth and cancer.
3. Some deletions are small, affecting only a few nucleotides, while others can encompass large segments of chromosomes, impacting multiple genes at once.
4. Detecting deletions often involves techniques like fluorescence in situ hybridization (FISH) or array comparative genomic hybridization (aCGH), which can reveal genetic imbalances.
5. In some cases, deletions may be inherited and predispose individuals to certain cancers, illustrating the importance of genetic counseling and testing.

Review Questions

• How do deletions affect tumor suppressor genes and their role in cancer development?
  • Deletions in tumor suppressor genes remove essential sequences necessary for regulating cell growth and division. When these genes are deleted, their protein products may no longer be available to inhibit excessive cell proliferation. This loss of control can lead to unchecked cellular growth and contribute significantly to cancer development, highlighting the critical nature of these genes in maintaining normal cellular functions.
• Discuss the methods used to detect deletions in chromosomes and their relevance in cancer diagnostics.
  • To detect deletions in chromosomes, techniques such as fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (aCGH) are commonly used. FISH utilizes fluorescent probes that bind specific DNA sequences, allowing visualization of chromosomal abnormalities. On the other hand, aCGH compares normal and tumor DNA to identify copy number variations. These methods are crucial for cancer diagnostics as they help identify genetic alterations associated with specific types of tumors.
• Evaluate the implications of inherited deletions on an individual's risk for developing certain types of cancer.
  • Inherited deletions can significantly elevate an individual's risk for developing specific cancers by predisposing them to loss-of-function mutations in critical tumor suppressor genes. For example, individuals with familial adenomatous polyposis often carry deletions in the APC gene that increase their risk for colorectal cancer. Understanding these genetic factors is vital for early detection, risk assessment, and implementing preventive measures through genetic counseling and testing.

Related terms

Mutation: A mutation is a change in the DNA sequence that can alter gene function, potentially leading to diseases, including cancer.

Oncogene: An oncogene is a mutated form of a proto-oncogene that has the potential to cause cancer when activated.

Chromosomal Aberration: A chromosomal aberration refers to any change in the normal structure or number of chromosomes, which can include deletions, duplications, and translocations.