Term
| what do HOX genes accomplish |
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Definition
they are transcription factors which are highly conserved and found in strings that always need to be translated in order
if these gene's get put into a different part of the body, they are so conserved and linked to each other that they will start to grow the body part they were originally intended for elsewhere
loss of HOX genes will make body parts incomplete up to the point of the gene deletions |
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Term
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Definition
caused by HOX mutations; results in extra fingers and toes bc a string of hox genes in found in extra copies or are over active in those regions of the body
HOXA13 mutation |
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Term
| foot-hand-genital syndrome |
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Definition
HOX gene abnormality where all of the above can be incomplete at points (short fingers or toes) hypospadia in males (hole on underside of penis)
HOXA13 mutation |
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Term
| what are PAX genes important for? name a disorder |
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Definition
| eye development; associated with aniridia and cataracts if PAX6 is mutated |
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Term
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Definition
split-hand and split foot malformation
NOT a HOX mutation
ectrodactyly (losing digits)
gene is localized to chromosome 7q
autosomal dominant |
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Term
| where is PAX 3 expressed? name a disease |
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Definition
it is expressed in the neural crest and other cells. related to auditory-pigmentary fxns, melanogenesis
WAARDENBURG SYNDROME (PAX 3)
characterized by:
-white forelock (partial albinism)
-lateral displacement of median canthi of eyes
-deafness*** |
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Term
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Definition
embryonic forebrain does not divide into two hemispheres
severe facial deformities, skull malformation and cleft lip in worst presentations
single median incisor is more mild forms
SHH (sonic hedgehog gene) which has been linked to ventral tube signaling has been implicated; most commonly seen in HPE type 3
autosomal dominant, and maybe linked to trisomy 13 |
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Term
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Definition
Autosomal Dominant and linked to advanced PATERNAL age
craniosynostosis (fusion of sutures) leading to flat-faced appearance, eye problems
can be repaired by surgery early on
FGFR2 responsible |
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Term
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Definition
| fibroblast growth factor receptor genes code for glycoproteins and are widely expressed in bone |
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Term
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Definition
Autosomal Dominant (but majority are linked to new mutations) and linked to advanced PATERNAL age
short stature with narrow trunk and short limbs, hypoplasia of midface, trident configuration of the hands
FGFR3 responsible
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Term
| treacher collins syndrome |
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Definition
antimonogloid slant of eyes, deformities of ears (any have hearing loss), hypoplasia of mandible and maxilla (tiny jaw)
***presentations can be very subtle tho
TCOF1 gene is cause; mutations lead to inadequate ribosomal RNA production in neural folds during embryogenesis |
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Term
| describe genomic imprinting |
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Definition
an allele can be imprinted during gametogensis so that later it will be expressed different in somatic cells; may be methylations or other means
this is one way an allele can be completely different from that received from another individual
since it might be methylated, it is usually inactivated in the embryo and the other parent's gene takes over
if the other parent's gene is deleted, then we have a problem |
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Term
| prader-willi and angelman's |
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Definition
both are diseases in which one allele is deleted and the other allele is imprinted at the 15q locus
PWS - obesity, overeating, underdeveloped gonads, MR
*mostly due to loss of paternal and imprinting of maternal
AS - happy puppet syndrome; large mandible and opened mouth expression, ataxic gait
*mostly due to loss of maternal and imprinting of paternal
***both have also be reported as a result of UPD (uniparental disomy) in which the two alleles are from the same parent |
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Term
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Definition
most common type is the OCA type II, mutation of P gene which is likely important in melanin transport
persons have no pigment in skin and eyes, skin cancers are common
autosomal recessive; quite common in equatorial Africa |
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