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Flashcards in Developmental Genetics Deck (56)
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1
Q

errors occurring in the initial formation of structures like cleft lip or polydactyly

A

malformation

2
Q

disturbances after an organ has been formed due to external forces and not genetics like shortened arms or legs due to vascular problem

A

disruptions

3
Q

mechanical distortions like club foot due to lack of amniotic fluid

A

deformation

4
Q

abnormalities in tissue organization like thanatophoric dysplasia

A

dysplasia

5
Q

cascades of effects

A

sequences

6
Q

groups of anomalies that consistently occur together due to a single underlying cause

A

syndromes

7
Q

traits coincide more often than expected with chance

A

association

8
Q

induces cell proliferation and involved in tissue patterning

A

sonic hedgehog genes

9
Q

type of patterning in sonic hedgehog genes

A

dorsal ventral patterning

10
Q

sonic hedgehog derived from

A

neural ectoderm such as notochord and ventral floor plate of neural tube

11
Q

zone of polarizing activity for sonic hedgehog genes

A

limb patterning

12
Q

sonic hedgehog involved in the development of what

A

hair follicles, tooth, lung, pancreas

13
Q

what role does sonic hedgehog play in the patched gli pathway

A

it binds to the PTCH and relieves the inhibition of SMO therefore activating downstream signaling

14
Q

what inhibits SMO in the patched gli pathway

A

PTCH

15
Q

how is sonic hedgehog prepared or modified before it binds to the PTCH

A

it is cleaved to an active N terminal form then cholesterol is added to it

16
Q

what happens when the Gli protein and CREBBP interact in the PTCH gli pathway

A

they activate gene expression by binding to the regulatory sequence on DNA

17
Q

where is SHH located on humans

A

distal long arm of chromosome 7

18
Q

heterozygous mutation of SHH results in what?

A

autosomal dominant holoprosencephaly

19
Q

clinical variability in people that present with holoprosencephaly

A

facial abnormalities (cyclopia, premaxillary agenesis, mild hypotelorism, or a single central maxillary incisor) to mild microcephaly alone.

20
Q

increased SHH in the frontal nasal prominence that promotes mediolateral expansion of the face and ventral forebrain

A

hypertelorism

21
Q

what does HOX gene pattern

A

anterior-posterior of the vertebrate embryo and limb bud

22
Q

what activated HOX gene expression

A

gradient of SHH which is created by ZPA (zone polarizing activity)

23
Q

what leads to polydactyly

A

overexpression of SHH in the limb bud and mutation in the Gli3

24
Q

holoprosencephaly is caused by a mutation where

A

in the SHH or Six3 gene

25
Q

mild effects such as single incisor, moderate effects such as cleft lip and palate, to severe effects such as cyclopia are all what?

A

variability in SHH mutation (SN: there is no correlation between specific mutation in SHH and phenotype)

26
Q

mutation in 7 dehydrocholesterol reductase

A

Smith Lemi Optiz Syndrome (SLOS)

27
Q

SLOS phenotype

A

microcephaly, mental retardation, malformation of mesodermal origin, syndactly, and polydactyly

28
Q

mutation in patched (ptc)

A

gorlin syndrome (nevoid basal cell carcinoma)

29
Q

rare mutation in gli gene

A

pallister hall syndrome (brain tumors and polydactyly)

30
Q

mutation in CREBBP gene

A

Rubinstein-Taybi Syndrome

31
Q

broad thumbs and toes, mental disability, short stature, small head, facial features

A

mutation in CREBBP gene

32
Q

patterning of anterior posterior body axis is done by

A

overlapping HOX gene expression

33
Q

what happens if there is a mutation in the hox genes in fruit fly

A

unusual transformation of body segment identity

34
Q

why doesn’t a mutation in mammalian hox genes show dramatic changes

A

because we have other hox genes/clusters that will come in and take the place of a mutated one

35
Q

in humans what happens if there is a single loss of a hox gene

A

it increases childhood susceptibility to leukemia

36
Q

what must be done to see a dramatic change in mammalians

A

must completely knock out all the hox genes in that area

37
Q

children with extra cervical rib have a higher frequency for cancer than general population so what does that mean

A

low reproductive fitness

38
Q

polydactyly is a result of what

A

disruption in hoxd13 gene

39
Q

achondroplasia is a result of mutation where

A

FGFR3 (fibroblast growth factor receptor 3) with a G-C transversion at nucleotide 1138 ath the transmembrane domain

40
Q

80% of achondroplasia is due to what?

A

80% - spontaneous mutation during spermatogenesis

20% - inherited from one parent

41
Q

how do chondrocytes develop

A

sequentially through reserve (R), proliferating (P), prehypertropic (PH), and hypertropic stages

42
Q

function of FGFR3

A

inhibit chondrocyte growth and differentiation in the growth plate of developing long bones

43
Q

in achondroplasia, there is a substitution of what and where

A

arginine replaced with glycine at position 360 on the FGFR3 protein

44
Q

less severe to most severe mutation of FGFR3 mutation

A

hypochondroplasia, achondroplasia, SAADAN dyplasia, thanatophoric dysplasia

45
Q

hypochondroplasia is mutation where

A

proximal (more common) and distal tyrosine kinase domain

46
Q

thanatophoric dysplasia is mutation where

A

extracellular domain and distal tyrosine kinase domain (lethal)

47
Q

what is deleted in infertile male

A

Regions AZFa, b, c (azoospermia factor)

48
Q

what happens in presence and absence of Y chromosome

A

presence - testes develop

absence - ovaries develop

49
Q

gonadal differentiation is determined by

A

presence or absence of SRY gene located on Y chromosome that produces testis determining factor (TDF)

50
Q

what does testis produce

A

anti mullerian duct hormone that destroys mullerian duct and testosterone

51
Q

46 XX Male sydrome (de la Chapelle syndrome) is caused by what

A

translocation of the SRY gene on the Y chromosome due to unequal crossing over during meiosis (Y translocated onto X)

52
Q

characteristics of de la chapelle syndrome

A

10% hypospadias, mullerian tissue absent, short, infertile

53
Q

46 XY female Swyer syndrome (pure gonadal dysgenesis) is caused by

A

loss of function mutation of SRY gene

54
Q

characteristics of Swyer syndrome

A

normal femae genitalia, mullerian ducts present, LH increased so clitoromegaly, bilateral streak gonads instead of ovaries or testes, delayed puberty

55
Q

treatment of swyer syndrome

A

estrogen and progesterone, streak gonads removed

56
Q

polymorphic markers on Y chromosome has been used to trace whom

A

human from their migration from Africa