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Biochemistry > Exam 5: Genetics of Development - Principles > Flashcards

Exam 5: Genetics of Development - Principles Flashcards

1
Q

anterior/posterior axis

A

first visible structure in embryo

defined by primitive streak, marks groove at which ectodermal cells form 3 germ layers

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2
Q

axes in the developing limb

A

shoulder-to-fingertip is proximal-distal
thumb-to-fifth-finger is anterior-posterior
dorsum-to-palm is dorsal-ventral

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3
Q

blastocyst

A

hollow sphere containing group of cells called inner cell mass
16 cell embryo (morula) transforms into blastocyst

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4
Q

chordin

A

secreted from cells in node and induce dorsal development in concentration-dependent manner

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5
Q

clinical dysmorphology

A

describes etiology of birth defects and gives valuable clues about underlying abnormality in development process

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6
Q

deformations

A

result from extrinsic influence on development of affected tissue
defect from outside
lack of amniotic fluid constrains fetus because not enough room to expand - can lead to contractures of limbs

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7
Q

disruptions

A

destruction of developing tissue

amniotic bands sometimes wrap around developing fetal limbs, choke off their blood supply & tissue is destroyed

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8
Q

ectoderm

A

develops from epiblast

forms skin and nervous system

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9
Q

embryonal period of development

A

after fertilization of an egg, begins with 4 cell divisions without cell growth
lasts from week 1 to week 8

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10
Q

endoderm

A

forms gut and lung epithelium

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11
Q

epiblast

A

formed from inner cell mass

goes on to form the embryo - upper cell layer

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12
Q

formin and renal aplasia

A

mutation in formin gene in mice causes renal aplasia in about 20% of mice
All mice were genetically and environmentally identical - means another cause of reduced penetrance
formin mutation can be tolerated - formin mutation does not cause, but rather increases probability for developing renal aplasia

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13
Q

gastrulation

A

produces primitive streak - first axis of embryo

creates three germ layers - endoderm, mesoderm, and ectoderm

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14
Q

homeobox genes (HOX)

A

determines patterning (division into segments to define part development) along anterior/posterior axis
family of transcription factors - contain homeodomain, a DNA binding domain
4 HOX clusters on 4 chromosomes
expression of each of genes in cluster correlates with position of cell and timing of expression
Each cell along axis experiences different ration of expression of different HOX genes - code for fate of cell

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15
Q

homeodomain

A

DNA binding domain contained in homeobox (HOX) genes

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16
Q

inner cell mass

A

in blastocyst - forms epiblast

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17
Q

isolated anomalies

A

affect a single body region
usually either sporadic or multifactorial
about 60% of major birth defects
i.e. cleft palate

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18
Q

major anomalies

A

anomalies with surgical or cosmetic consequences, like cleft lip or amputated limb

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19
Q

minor anomalies

A

have little impact on well being of patient

give important diagnostic clues about presence of a syndrome

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20
Q

malformations

A

result from intrinsic abnormality in developmental process

defect comes from within

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21
Q

mesoderm

A

form bone, muscles, and most internal organs

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22
Q

morula

A

16 cell embryo

transforms into blastocyst

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23
Q

mosaic phase

A

begins after gastrulation
loss of a cell in this phase cannot be compensated - will lead to loss of tissue
affects baby - removal of cells for screening needs to be done before this phase

24
Q

regulative phase

A

cells functionally equivalent - loss of a part of embryo can be compensated for by neighboring cell
ends with gastrulation

25
Q

nodal

A

gene required for formation of primitive streak & later for formation of left/right axis
soluble protein secreted into extracellular space - diffuses through tissue and establishes gradient - NOT a transcription factor (because it can leave the cell)

26
Q

noggin

A

protein secreted from cells in the node

induce dorsal development in concentration-dependent manner

27
Q

polydactyly

A 
extra digits (in hands/feet)
mutations interfere with developmental process of limbs
originate from defect within affected organ - malformation
28
Q

primitive streak

A

defines first axis of embryo, produced by gastrulation

marks groove at which ectodermal cells invade space between epiblast and hypoblast to form 3 germ layer

29
Q

Robin sequence

A

causes cleft palate
extrinsic constraint on fetus (from low amount of amniotic fluid) interferes with growth of jaw - small chin
tongue pushes into forming hard palate & blocks formation - forms u-shaped cleft palate

30
Q

segmental overgrowth

A

consequence of dysregulation during development - can occur from just one additional cell division per affected cell - loss of control over cell division

31
Q

sequence

A

cascade of events
starts from isolated anomaly and leads to multiple malformations - usually sporadic or multifactorial
phenotypes caused sequentially by singe defect

32
Q

syndrome

A

affect several body regions and most often display chromosomal or Mendelian inheritance
present when disease phenotypes are caused by single defect simultaneously

33
Q

situs ambiguus

A

caused by defects in left/right axis formation
serious condition in which orientation of organs is randomized
usually accompanied by heart defects

34
Q

situs inversus

A

caused by defects in left/right axis formation
all of organs are in complete mirror image of where normally found
usually asymptomatic

35
Q

Sonic hedgehog (Shh)

A

signaling protein from notochord (precursor of spine) left/right asymmetry caused by asymmetric expressions of this gene - leads to left side expression of nodal, which initiates left-looping of heart tube

36
Q

Dorsal/ventral axis

A

specified by noggin and chordin in concentration dependent manner

37
Q

time of implantation

A

day 7 to 12

38
Q

Treacher-Collins Syndrome

A

autosomal dominant
small jaw, down slanting palpebral fissuers, malar hypoplasia, cleft palate
risk for complications is high and surgery risky

39
Q

VACTERL association

A

Vertebral, Anal atresia, Cardiac, Tracheo=Esophagal fistula, Renal and Radial Limb defects)
abnormality that occurs during first 1-4 weeks of development causes multiple major abnormalities in entire embryonic regions
originates from damage to developing mesoderm at 20-25 days after conception
maternal diabetes is a major risk factor

40
Q

Abnormalities occurring from week 5 to 8

A

affect specific organs & produce single major anomalies - congenital heart defects

41
Q

Abnormalities occurring after week 9

A

have mild effect on individual

42
Q

What percentage of children are born with a birth defect?

A

2-3%

43
Q

What is the percentage of mortality of children with birth defects?

A

20%, most common cause of infant death in US

44
Q

What are the most common birth defects

A

Heart defects, pyloric stenosis, neural tube defects, orofacial clefts, clubfoot

45
Q

What is the prevalence of heart defects?

A

1/100 - 1/200 live births

46
Q

What is the prevalence of pyloric stenosis?

A

1/300

47
Q

What is the prevalence of neural tube defects?

A

1/1,000

48
Q

What is the prevalence of orofacial clefts?

A

1/700 - 1/1,000

49
Q

What is the prevalence of club foot?

A

1/1,000

50
Q

Percentage of birth defects with complex/ multifactorial inheritance

A

50%, no identifiable cause

51
Q

Percentage of birth defects caused by chromosomal defects

A

25%

52
Q

Percentage of birth defects caused by single-gene mutations

A

20%

53
Q

Percentage of birth defects caused by non-genetic factors (maternal medication and infections

A

5%

54
Q

pre-implantation diagnosis

A

in morula phase (before mosaic phase) a cell can be removed from embryo and examined for chromosomal aberrations without harming embryo
15 remaining cells develop into normal embryo

55
Q

5 processes by which cells participate in development

A

Gene regulation by transcription factors and chromatin modification
Cell-cell signaling, either by direct contact or by secretion of morphogens
Development of specific cell shape and polarity
Movement and migration of cells
Programmed cell death

56
Q

robustness

A

countering of factors capable to disturb orderly development

recognized by cell and regulatory mechanisms used

Biochemistry (15 decks)

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