HLTB20H3 Lecture Notes - Lecture 5: Patau Syndrome, Dermatoglyphics, Quantitative Trait Locus
HLTB20 TUT05
*Dermatoglyphics on exam; not correlation
Slide 3
• Monozygotic (MZ) twins can have the exact same or similar fingerprints;
depends on the maternal environment
• Fingerprints (a huge percentage) is based on genetics
• Galton → Eugenics movement: Controlled breeding to breed desire traits and to
breed out undesired traits
o Also responsible for introducing the epidermal patterns: the outer layer
of the skin
• Triradii: Group of ridges on your fingerprints that form a Y shape
Slide 4
• 1) Formed by the 3rd to 4th month of fetal life (in utero); do not change
thereafter, it just increases in size
• 2) Variability can be seen on the inter- and intra- population levels
• 3) Quantitative – correlation (r) analysis
• 4) Trisomy 13 → Genetic disorder where the individual has three copies of the
chromosome 13 instead of two
o Trisomy 14, 15, 21 – extra three chromosome at different points
o Klinefelter’s – affects male, has an additional X to their XY → XXY
▪ Tall and slender, physically
▪ Have more feminine qualities (ex. enlarged breast)
o Turner’s – affect females; have one X chromosome, instead of two
▪ Developmental abnormalities
▪ Be infertile
• 5) Conditions can lead to different fingerprints
o The fingerprint patterns can be used as diagnostic criteria to test which
disease that have
o Caused by multiple genes (polygenic inheritance)
Slide 5
• Proximal → Closer to your body
• Whorls (on the thumb) have two triradii
Slide 6
• To get the ridge count (only for the whorl) you should count both ends
• Count the ridges from the triradii and you would take the higher value
o If you get 4 ridges and 5 ridges; total – add 4 and 5 to get 9
• Fragments of ridges should be included in the count
Slide 7
• Only need to do one triradii
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