Chromosomal Genetic Disorders Quiz

Chromosomal Genetic Disorders

• Result from mutations affecting genes or an incorrect amount of genetic material.
• Mutations are harmful changes to a gene, often caused by errors during cell division or exposure to DNA-damaging agents like chemicals, radiation, and UV light.

Types of Mutations

• Point mutations involve a single base change in DNA.
  • Substitution: One base is replaced with another.
    • Example: Sickle cell anemia results from a substitution mutation in the gene for hemoglobin.
  • Insertion: Extra nucleotides are added to the DNA sequence.
  • Deletion: One or more nucleotides are removed from the DNA sequence.
    • Example: Cystic fibrosis is caused by a deletion mutation in the CFTR gene.

Chromosomal Mutations

• Affect the structure or number of chromosomes.
  • Deletion: A part of a chromosome is lost, removing all genes in that segment.
  • Duplication: A segment of a chromosome is repeated, increasing the concentration of genes in that area.
    • Example: Duplication of genes can contribute to cancer development.

Meiosis and Chromosomal Disorders

• Meiosis is the process of cell division that creates gametes (sperm and egg).
• Meiotic nondisjunction occurs when homologous chromosomes fail to separate properly during meiosis, resulting in gametes with an incorrect number of chromosomes.
• Aneuploidy refers to an abnormal number of chromosomes.
  • Trisomy: Presence of an extra chromosome.
  • Monosomy: Absence of one chromosome.
  • Deletions: Missing pieces of chromosomes or genetic material.
  • Translocations: Pieces of chromosomes break off and reattach to another chromosome.

Trisomy 21/Down Syndrome

• Caused by the presence of an extra copy of chromosome 21.
• Signs and symptoms:
  • Distinctive facial features (slanted eyes, flat nasal bridge, small mouth).
  • Flexible joints and weak muscles.
  • Inwardly curved little finger (clinodactyly).
  • Wide space between big and second toe.
  • Short stature.
  • Small hands and feet.
  • Single, deep crease across palm (simian crease).

Cri-du-chat Syndrome

• Also known as 5p- Syndrome, it results from deletion of a piece of chromosome 5.
• Signs and symptoms:
  • High-pitched cry resembling a cat's meow.
  • Mental retardation.
  • Delayed development.
  • Distinctive facial features (small head, widely spaced eyes).
  • Low birth weight and weak muscle tone.

Turner Syndrome

• Genetic condition affecting females where one X chromosome is missing or partly missing.
• Affects physical development and reproductive system.
• Signs and symptoms:
  • Short stature.
  • Webbed neck.
  • Infertility.
  • Heart defects.