Genetics of development

Question 1

When the zygote divides into 16 cells, what does it then become?

Answer 1

Morula

Question 2

What does the morula turn into?

Answer 2

Blastocyst

Question 3

What two layers of cells does the blastocyst form?

Answer 3

Epiblast and hypoblast cells

Question 4

Which layer of cells develops into the embryo?

Answer 4

Epiblast cells

Question 5

What are the three layers of cells derived from epiblast cells?

Answer 5

Ectoderm, mesoderm, endoderm

Question 6

what is the first axis of the embryo?

Answer 6

primitive streak

Question 7

When can cells of the developing embryo be mutated and have the remaining cells compensate for it?

Answer 7

Regulative phase (up until primitive groove formation I think)

Question 8

What is the phase of development after the regulative phase?

Answer 8

Mosaic phase

Question 9

What are the three axes that are defined in the developing embryo?

Answer 9

crainial-caudal
dorsal ventral
left-right

Question 10

What is the first axis to be developed in the embryo? What is it defined by?

Answer 10

anterior/posterior

primitive streak

Question 11

Where do ectodermal cells invade into the space between the epiblast and hypoblast cells?

Answer 11

primitive streak

Question 12

Where is the node of the primitive streak?

Answer 12

At the anterior end

Question 13

What are the proteins that are secreted to specify the cranial/caudal ends?

Answer 13

noggin and chordin

Question 14

What is the protein that causes the left/right axis to develop due to its unequal secretion at either end?

Answer 14

Sonic Hedgehog

Question 15

Where is the sonic hedgehog protein produced from?

Answer 15

notocord

Question 16

What protein is secreted from the left side of the notocord and is responsible for development of that side?

Answer 16

nodal

Question 17

A defect in the right/left axis development that leads to the inversion of all of the internal organs is called what?

Answer 17

situs inversus

Question 18

What is situs ambiguus?

Answer 18

Random dispersal of internal organs

Question 19

In the axis of the embryonic limb the thumb to the fifth finger is designated what?

Answer 19

Anterior/posterior

Question 20

What is the process of patterning?

Answer 20

The process by which the developing embryo divides up what part of the developing cell mass become thorax, abdomen, head etc.

Question 21

Patterning along the anterior/posterior axis is determined by what genes?

Answer 21

the homeobox genes (HOX)

Question 22

How does HOX determine the anterior/posterior axis?

Answer 22

different ratio of expression at different sites

Question 23

What are the 5 cellular mechanisms operating in development?

Answer 23

1. Gene regulation by transcription factors/chromatin modification
2. Cell-cell signalling
3. development of specific cell shape and polarity
4. movement and migration of cells
5. programmed cell death

Question 24

What are malformations?

Answer 24

Problems with development that result from an intrinsic abnormality in the development process

Originate from the organ itself

Question 25

What are deformations?

Answer 25

Problems with development that result from an extrinsic influence on the development of the affected tissue Do no originate from the organ itself

Question 26

What is oligohydraminos?

Answer 26

Lack of amniotic fluid during development?

Question 27

What are disruptions?

Answer 27

Problems with development that result from the destruction of developing tissue

Question 28

What are isolated anomalies?

Answer 28

anomalies that affect a single body region.

Question 29

What is a sequence in the context of birth defects?

Answer 29

It is a cascade of events that starts from an isolated anomaly, and leads to multiple malformations (phenotype)

Question 30

What are syndromes?

Answer 30

Phenotypes that affect several body regions; disease phenotype caused by a single defect simultaneously

Question 31

How are anomalies classified?

Answer 31

By the time at which they occur in development

Question 32

What are the most severe anomalies?

Answer 32

when they occur within the first 1-4 weeks of development

Question 33

What is the VACTERL association?

Answer 33

Vertebral, Anal atresia, Cardiac, Tracheo-Esophagal fistula, Renal/Radial defects, Limb defects

Question 34

What is the major risk factor for VACTERL?

Answer 34

Mother DM

Question 35

How do abnormalities occurring from week 5-8 present?

Answer 35

Specific organs affected, with single major abnormalities (congenital heart defects)

Question 36

How do abnormalities occurring after week 9 present?

Answer 36

mild effects

Question 37

How are MAJOR anomalies defined?

Answer 37

Anything the requires surgery or major cosmetic consequences

Question 38

How are MINOR anomalies defined?

Answer 38

Have little impact on the well-being of the patient.

Question 39

What percentage of children are born with genetic birth defects in the U.S.?

Answer 39

2-3%

Question 40

What percentage of infant mortalities are due to birth defects? Prematurity?

Answer 40

20%, 20%

Question 41

What are the five most common birth defects?

Answer 41

``` Heart defects (1/100-1/200) Pyloric stenosis (1/300) Neural tube defects (1/1000) Orofacial clefts (1/700-1/1000) Clubfoot (1/1000) ```

Question 42

What percentage of genetic defects have a complex inheritance? chromosomal defects? single gene mutations?

Answer 42

50% for complex 25% for chromosomal 20% for single gene 5% for nongenetic factors