How to Read a Karyotype

Understanding Karyotypes

• A karyotype is a picture of all the chromosomes in a person's genome.
• It showcases the entire genome, a full set of DNA with all genes influencing traits.
• Humans have 46 individual DNA molecules called chromosomes.
  • These chromosomes are arranged in 23 pairs (totaling 46 chromosomes).

Chromosomes

• Each person has two of each type of chromosome:
  • One from the mother's egg
  • One from the father's sperm
• Homologous Chromosomes:
  • Contain the same kinds of genes in the same locations.
  • Example: The COL11A1 gene is found on chromosome 1 across all humans.

Types of Chromosomes

• Autosomal Chromosomes (Autosomes):
  • Numbered 1 through 22.
  • Do not determine the sex of an organism.
• Sex Chromosomes:
  • Males: One X and one Y chromosome.
  • Females: Two X chromosomes.
  • The Y chromosome is smaller than the X chromosome.

Analyzing a Karyotype

• Total Chromosomes Count:
  • Ensure there are 46 total chromosomes.
  • Errors in egg/sperm production can lead to an abnormal number of chromosomes.

Chromosomal Abnormalities

• Monosomy: Missing one chromosome of a pair.
  • Example: Turner syndrome (only one X chromosome).
    • Results in physical abnormalities, infertility, and mental development issues.
• Trisomy: Extra chromosome in a pair (three chromosomes instead of two).
  • Example: Trisomy 21 (Down's Syndrome) - Three copies of chromosome 21.
    • Causes mental and physical developmental delays and shortened lifespan.

Chromosome Shape

• Analyzing the shape helps detect DNA loss or gain.
• Abnormal lengths indicate potential issues in gamete development.

Further Learning

• Additional resources available for understanding how monosomy and trisomy occur, such as videos on non-disjunction.