Genetic testing: Cytogenetics (not finish)

Question 1

2 types of chromosomal abnormalities

Answer 1

• Numerical ( trisomy eg)
• structural (balanced and unbalanced)

Question 2

What is the most common mutation in humans

Answer 2

Trisomy

Question 3

What are the three well-defined non-mosaic autosomal chromosome trisomy compatible with postnatal survival

Answer 3

trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), and trisomy 13 (Patau syndrome)

Question 4

Incidence of trisomy 21

Answer 4

Approximately 1 child in 850 is born with Down syndrome

Question 5

What is the single most common genetic disorder of moderate intellectual disability

Answer 5

Down syndrome

Question 6

Whay is the only etiological factor for which a link with aneuploidy is unequivocally recognized

Answer 6

Advance maternal age

Question 7

What means a “free” trisomy 21

Answer 7

there is an additionnal chromosone on the 21st pair of chromosome

Question 8

What is a Robertsonian translocation?

Answer 8

A Robertsonian translocation involves chromosomes 14 and 21 which is present with two normal 21’s. Hence there is an additional 21 in this karyotype. (two 21 on the 21st pair, and an extra 21 on the 14th pair)

Question 9

What shows the parental karyotype of a child affected by the robertsonian translocation?

Answer 9

the father can be a balanced carrier of the robertsonian translocation by having one chromosome on the 21st pair, and 3 on the 14th pair - number of chromosomes are in balance