Lecture 20: Diagnostics File

Question 1

name three types of testing (paternity) ?

Answer 1

pre-implantation - around conception (test-tube baby)
Pre-natal - in utero (amniocentesis/CVS/termination)
Predictive - late onset (HD & cancer)

Question 2

Explain pre implantation genetic diagnosis (PGD)

Answer 2

cell is removed from 8-cell embryo, tested for disorders and reimplanted.

Tested using PCR and standard techniques

Question 3

What are the cons of PGD?

Answer 3

expensive and low success rate (20%)

Question 4

Explain pre-natal diagnosis

Answer 4

Amniocentesis - Fetal cells from amniostic fluid are cultured and karyotyped

CVS (chronic villus sampling) - fetal cells taken from chronic villus tissue and sampled

Question 5

why is CVS usuall better than amniocentesis ?

Answer 5

CVS can be done earlier and is quicker

Question 6

What is syndromic ?

Answer 6

When one mutation leads to multiple phenotypes

Question 7

What is non-syndromic ?

Answer 7

When one mutation leads to one phenotype

Question 8

What does predictive diagnostics tell us ?

Answer 8

For HD = whether disease will develop, and approx age of onset

For cancer= level of risk

Question 9

What are connexins ?

Answer 9

component of gap junctions that are involved in cell-cell communication

Question 10

What is Connexin 26 (CX26)?

Answer 10

Inner ear epithelial gap junctions

Question 11

Explain mutations in CX26

Answer 11

Mutations are pre-lingual and autosomal recessive

Caused by a deletion of one G (35delG) that cause frameshift mutation

Question 12

WHat is ushers syndrome ?

Answer 12

most frequent deafblind syndrome, at least 12 genes all autosoma recessive. Blindness is progressive so must be diagnosed early