Embryology and Genetics

Question 1

where does the male duct system originate from

Answer 1

mesonephric

Question 2

where does the female duct system originate from

Answer 2

paramesonephric

Question 3

what controls the descent of the testes to the scrotum

Answer 3

gubernaculum

Question 4

what else does gubernaculum help the descent of and where does it pull it to

Answer 4

the ovaries

they are pulled into a peritoneal fold

Question 5

what stage does external genitalia have before male/female differentiation

Answer 5

indifferent stage

Question 6

what contributes to the urinary, reproductive AND GI systems

Answer 6

the cloaca

Question 7

what happens in the 3rd week in relation to development of the external genitalia

Answer 7

cloacal folds form fusing cranially to form genital tubercle

Question 8

what happens in the 6th week in relation to development of the external genitalia

Answer 8

cloacal membrane divided into urogenital and anal membranes:

cloacal folds also divide into urethral and anal folds

Question 9

what do the genital swellings form

Answer 9

scrotum (males) or labia major (females)

Question 10

what is a possible abnormality between the urogenital system and hindgut and why can this happen

Answer 10

fistulae between urogenital system and rectum/anal canal

common origin

Question 11

from what gestation week can amniocentesis be done

Answer 11

16+ weeks

Question 12

from what gestation week can chorionic villus biopsy be done

Answer 12

11.5 weeks

Question 13

from what gestation week can fetal blood sampling be done

Answer 13

18+ weeks

Question 14

from what gestation week can fetal DNA be acquired from maternal blood

Answer 14

8+ weeks

Question 15

what is the definition of a mutation

Answer 15

genetic change that causes disease

Question 16

what is the definition of a polymorphism

Answer 16

Genetic Variation that is not per-se disease causing

Question 17

what current prenatal screening in Scotland

Answer 17

Dating Ultrasound Scan with serum biochemistry – around 12 weeks

Serum Screening at around 16 weeks - maternal blood test to look for biochem markers of Down Syndrome

20 week detailed scan - looks for other fetal abnormalities

Question 18

what is the genetic name for Down Syndrome

Answer 18

Trisomy 21

Question 19

what are the best tests for Ix for Down Syndrome

Answer 19

Amniocentesis
array CGH [aCGH]

• 18 week gestation

Question 20

what can aCGH detect

Answer 20

small deletions such as 22q11 deletion

Question 21

what the definition of a balanced chromosome rearrangement

Answer 21

all the chromosomal material is present

Question 22

what the definition of a unbalanced chromosome rearrangement

Answer 22

Extra or missing chromosomal material. Usually 1 or 3 copies of some of the genome.

Question 23

what is the definition of Robertsonian translocation

Answer 23

Two acrocentric chromomosomes stuck end to end

Question 24

ultrasound scanning - booking, detailed, cardiac anomalies, microcephaly, short limbs

Answer 24

Booking Scan - 10-12 weeks
Detailed Scan - 20 weeks
Cardiac - 12-20 weeks
Microcephaly - after 22 weeks
Short limbs - after 22 weeks

Question 25

what genetic inheritance is DMD

Answer 25

x-linked recessive

Question 26

What is risk that a child 
is affected with DMD if the mother is a carrier

Answer 26

1 in 4

[1 in 2 if you know its a boy]

Question 27

what is the risk of a child acquired an autosomal recessive trait

Answer 27

1 in 4

Question 28

what is the risk of a child acquired an autosomal dominant trait

Answer 28

1 in 2

Question 29

when can a Chorionic Villus Biopsy be done

Answer 29

@ 11.5 + weeks

Question 30

when can an Amniocentesis be done

Answer 30

@ 16 weeks

Question 31

what is the embryo called on day 4 of development

Answer 31

morula

Question 32

what is the embryo called on day 5 of development

Answer 32

blastocyst