Karyotyping Activity Study Notes

Karyotyping Activity Overview

  • Purpose: To interpret a karyotype and make a diagnosis for Patient B.

Patient B's Karyotype Information

  • Outcome: The activity involves compiling and analyzing a karyotype to identify chromosomal abnormalities.
  • Reference karyotype: Patient B's karyotype is included at the bottom of the activity page for reference.

Interpreting the Karyotype

  • Karyotype Notation:

    • Lab technicians utilize a specific notation that indicates:
    • Total number of chromosomes
    • Sex chromosomes
    • Any extra or missing autosomal chromosomes

  • Examples of Karyotype Notations:

    • 47, XY, +18
    • Interpretation: 47 chromosomes total, male, one extra copy of chromosome 18
    • 46, XX
    • Interpretation: 46 chromosomes total, female, normal karyotype
    • 47, XXY
    • Interpretation: 47 chromosomes total, female, one extra sex chromosome

  • Question B1: What notation would you use to characterize Patient B's karyotype?

Making a Diagnosis

  • Diagnosis Process: The next step is to either:

    • Diagnose a chromosomal abnormality
    • Rule out chromosomal abnormalities.

  • Normal Chromosome Count: In individuals with a normal karyotype:

    • Each pair of chromosomes should contain only two individual chromosomes.

  • Implications of Abnormal Chromosome Count:

    • Having an extra or missing chromosome generally leads to fetal inviability.
    • If the fetus does survive to term, it may present unique clinical features.

  • Common Syndromes Associated with Chromosomal Abnormalities:

    • Klinefelter's Syndrome:
    • Diagnosis: One or more extra sex chromosomes (i.e., XXY)
    • Down's Syndrome (Trisomy 21):
    • Diagnosis: Extra chromosome 21
    • Trisomy 13 Syndrome:
    • Diagnosis: Extra chromosome 13

  • Question B2: What diagnosis would you give Patient B?

Patient B's History

  • Demographics: Patient B is a 28-year-old male.
  • Concern: The primary reason for examination is to determine a cause for his infertility.
  • Sample Collection: Chromosomes were obtained from:
    • Nucleated cells in the patient's blood.

Visual Representation of Patient B's Karyotype

  • Karyotype Numbering:
    • 670, 2, 3, 8, 0, 5, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22
  • Sexual Chromosomes: Indicated by XX/XY.