Abnormalities in Chromosome Number (Self and Lecture)

Question 1

What is trisomy 21

Answer 1

Down Syndrome

Question 2

What causes trisomy 21

List 3 Things

Answer 2

Meiotic Nondisjunction 95% of the time in maternal meiosis 1. 2-4 % of the time it will be a mosaicism, and robertsonian translocation

Question 3

What is the prevalence of the disease ?

Answer 3

1 in 800 live births and only 20% make it to a live birth

Question 4

What is trisomy 18

Answer 4

Edwards syndrome, rocker bottom feet and clenched hands, prenatal growth deficiency and congenital heart defects.

Question 5

What causes trisomy 18 ?

Answer 5

(47 XX +18) ( or 47 XY, +18) caused by maternal nondisjunction.

Question 6

What is the incidence of trisomy 18 ?

Answer 6

1 in 6000 live births less than 5% make it to survival

Question 7

What is Patau Syndrome ?

Answer 7

Trisomy 13- results in abnormal development of the mid face, eye, and forebrain. Polydactaly, Microphyhalmia, congenital heart defects.

Question 8

What causes Patau Syndrome ?

Answer 8

80% maternal nondisjunction
<20% Robertsonian Translocation involving chromosome 13.
-Rare cases of mosasicism

Question 9

What has more serious phenotypes, Sex Chromosome abnormalities or somatic abnormalities ?

Answer 9

Sex chromosome abnormalities are much less severe. We all only have one active X because of X inactivation. ***YOU have to have atleast 1 X to survive

Question 10

What is turners syndrome ?

Answer 10

Primary Hypogonadism characterized by short stature and ovarian dysgenesis.

Question 11

What causes Turner Syndrome ?

Answer 11

45X and variants. caused by paternal nondisjunction and is not associated with advanced age.

Question 12

What is Klinefelter Syndrome ?

Answer 12

47XXY (85%)

15% can have mosaicism (46 XY / 47, XXY)

Question 13

What causes Klinefelter syndrome ?

Answer 13

50 % paternal nondisjunction (XY)
50% Maternal nondisjunction
1/1000 male live births, 1/2 are spontaneously aborted.

Question 14

What will a kid with klienfelter syndrome look like ?

Answer 14

Mostly in males, 
Primary hypogonadism 
Tall with long extremities
Gynecomastia 
Reduced IQ

Question 15

What is triple X syndrome ?

Answer 15

47XXX
1/1000 female live births
90% maternal nondisjunction with age effect
Normal phenotype with mild learning problems

Question 16

What is 47 XYY syndrome ?

Answer 16

Paternal meiosis 2 nondisjunction, no age effect

Normal phenotype, tall, educational and behavioral problems

Question 17

Is the incidence of down syndrome higher in young or old mothers?

Answer 17

Young