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Flashcards in Genetics of development Deck (42):
1

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

Morula

2

What does the morula turn into?

Blastocyst

3

What two layers of cells does the blastocyst form?

Epiblast and hypoblast cells

4

Which layer of cells develops into the embryo?

Epiblast cells

5

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

Ectoderm, mesoderm, endoderm

6

what is the first axis of the embryo?

primitive streak

7

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

Regulative phase (up until primitive groove formation I think)

8

What is the phase of development after the regulative phase?

Mosaic phase

9

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

crainial-caudal
dorsal ventral
left-right

10

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

anterior/posterior
primitive streak

11

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

primitive streak

12

Where is the node of the primitive streak?

At the anterior end

13

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

noggin and chordin

14

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

Sonic Hedgehog

15

Where is the sonic hedgehog protein produced from?

notocord

16

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

nodal

17

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

situs inversus

18

What is situs ambiguus?

Random dispersal of internal organs

19

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

Anterior/posterior

20

What is the process of patterning?

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

21

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

the homeobox genes (HOX)

22

How does HOX determine the anterior/posterior axis?

different ratio of expression at different sites

23

What are the 5 cellular mechanisms operating in development?

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

24

What are malformations?

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

Originate from the organ itself

25

What are deformations?

Problems with development that result from an extrinsic influence on the development of the affected tissue

Do no originate from the organ itself

26

What is oligohydraminos?

Lack of amniotic fluid during development?

27

What are disruptions?

Problems with development that result from the destruction of developing tissue

28

What are isolated anomalies?

anomalies that affect a single body region.

29

What is a sequence in the context of birth defects?

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

30

What are syndromes?

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

31

How are anomalies classified?

By the time at which they occur in development

32

What are the most severe anomalies?

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

33

What is the VACTERL association?

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

34

What is the major risk factor for VACTERL?

Mother DM

35

How do abnormalities occurring from week 5-8 present?

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

36

How do abnormalities occurring after week 9 present?

mild effects

37

How are MAJOR anomalies defined?

Anything the requires surgery or major cosmetic consequences

38

How are MINOR anomalies defined?

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

39

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

2-3%

40

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

20%, 20%

41

What are the five most common birth defects?

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

42

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

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