Genetics Lecture 9 - Cytogenetics I

Question 1

Which trisomies are compatible with life?

Answer 1

Trisomy 13, 18, 21. +X and +Y are also.

Question 2

Which monosomies are compatible with life?

Answer 2

Monosomy X

Question 3

What are the clinical features of Patau syndrome (Trisomy 13)?

Answer 3

Cleft lip, palate, scalp defects, polydactyly, very poor prognosis (only 5% survive to six months)

Question 4

What are the clinical features of Trisomy 18 (Edwards syndrome)?

Answer 4

Rocker bottom feet, overlapping fingers, small size, microcephaly, poor prognosis (5% live beyond one year)

Question 5

What are the clinical features of Trisomy 21?

Answer 5

Single palmar crease, hypotonia, upslanted palpebral fissures, flat facial profile, ID, congenital heart defects, sandal toe.

Question 6

What are the clinical features of Klinefelter syndrome? What is the karyotype?

Answer 6

47, XXY. Gynecomastia (after puberty), infertility, tall stature, long limbs.

Question 7

What are the clinical features of Turner syndrome? What are the karyotypes?

Answer 7

45, X (50%)
46, X, (del Xp) - p arm deletion
46, X, i(Xq) - isochromosome (two q arms)
46, X, r(X) - ring x (fusion of ends of X chrom)
Features are webbed neck, wide hypoplastic nipples, infertility, short stature.

Question 8

What is trisomic rescue? What can it result in?

Answer 8

When cells identify three chromosomes and throw one out. Can result in uniparental disomy.