Chromosomes II Flashcards
What is clinical cytogenetics?
Study of rs of chromosomal alteration and genetic disease in humans
Describe Down’s Syndrome
AKA Trisomy 21 - extra chromosome at 21
Mostly comes from mother, cuases delayed physical/mental development at head/facial features
Congenital heart defects, digestive problems, hearing/vision, leukemia
Survive average 49
Describe the features of someone with Down Syndrome
Flattened nose/face, upward staring eyes, short pinky finger curves inwards, widely separated 1/2nd toe
Describe Edward’s Syndrome
AKA Trisomy 18
Extra chromosome from mother if pregnant after 35yrs, mostly girls affected
Causes small muscles,underdeveloped, mental delay, problems in: Heart, Lungs, Digestive tract, Kidneys
Usually death before/1st week, 5% live past 1yr
Describe the features of someone with Edward’s Syndrome
Small mouth, jaw, short neck, large skull at the back, malformed ears, clenched hands/overlapping fingers, club foot
Describe Patau’s syndrome
AKA Trisomy 13 due to pregnancy after 35yrs
Small, severe brain, eye/facial and heart defects, hypotonia, severe intellectual disability
No treatment, death in 1st days/week, 5% live past 1yr
Describe the features of someone with Patau’s Syndrome
Small head, no brows, cleft lip/palate, malformed ears, clenched hands/polydactyly, abnormal testes
What is prenatal chromosomal analysis?
Identifying human chromosome abnormalities
What are the 3 type of prenatal chromosomal analysis?
Chorionic villus sampling (CVS)
Amniocentesis
Blastomeres (after IVF)
Describe CVS
Done 11-14 weeks of pregnancy
Tissue sample taken from placenta
Fine needle passed through abdomen into uterus to take sample
What is the chorionic villi?
Tissue before it becomes placenta
Describe amniocentesis
Done 15-20 weeks of pregnancy
Needle pushed through abdomen through uterus into amniotic fluid
AF (10-20ml) has cells shed from foetus thats tested
Sample shouldn’t be stained with blood
What does a nuchal translucency ultrasound show?
The baby and the distance between the bay’s head and the abdominal wall of the uterus, amount of AF between
What are the different types of molecular cytogenetic techniques?
Fluorescence in situ hybridisation (FISH)
Multiple-FISH or Spectral Karyotyping (SKY)
Array based comparative genomic hybridisation (aCGH)
Describe FISH
Shows DNA sequences to specific regions of human chromosomes, uses fluorescently labelled DNA probes that hydbridise complementary chromosomal regions
Forms fluorescent dot on chromosome where labelled probe binds
Allows higher level of resolution than standard G-banding approaches
