1 congenital defects Flashcards
What is a deformation?
“distortion of a structure by mechanical force, e.g. club foot
What is a dysplasia?
“abnormal organization of tissue e.g. thanatophoric dysplasia”
What is a malformation?
“primary structural defect, e.g. cleft lip”
.
What is a disruption?
“extrinsic factor affecting normal development, e.g. digital amputation
”
.
What is a syndrome?
“consistent pattern of abnormalities, e.g. Down’s syndrome
”
What is a sequence?
“multiple abnormalities initiated by primary factor, e.g. Potter’s sequence”
What is an association?
“– non-random occurrence of clinical features not explained by sequence or syndrome, e.g. VATER syndrome”
What is a dismorphism?
“unusual or abnormal physical feature (sometimes as part of a genetic syndrome), e.g. hypertelorism
”
Name common aneuploidies?
“21 (Down syndrome) Trisomy 18 (Edwards’ syndrome) Trisomy 13 (Patau syndrome) Monosomy X (Turner’s syndrome) XXY (Klinefelter’s Syndrome) XYY and XXX ”
What are the 7 abnormalities?
Deformation Dysplasia Malformation Disruption Sequence Syndrome Association Dimorphism
3 types of chromosomal abnormalities?
Numerical–aneuploidy–lossofgainofachromosome
Structural–translocations,deletions,insertions,inversions,rings o Mosaicism– different cell lines
What are the common symptoms of down’s syndrome
Newbornperiod–severehypotonia,sleepy,excessnuchalskin
o Craniofacial – macroglossia (big tongue), small ears, epicanthic folds, upward sloping
palpebral fissures (gap between the upper and lower eyelids), Brushfield spots (white spots
in iris)
o Limbs–singlepalmarcrease,widegapbetweenfirstandsecondtoes o Cardiac–atrialandventricularseptaldefects
o Other–shortstature,duodenalatresia–abnormallyclosed
How common are congenital abnormalities
1 in 50 births
What does reduced amniotic fluid lead to
Potter’s sequence
How does the centromere determine the type of chromosome
Ifthecentromereisexactlyinthemiddle,itiscalledmetacentric
o Ifthecentromereisjustoffmiddle,itiscalledsubmetacentric
o If the centromere is not on the middle, it is called acrocentric, with the small ends of the chromatids called satellites
Give a stain used for karyotypes
Giesma
How is the chromosome band written
Chromosome number
P or Q arm
Band number ( up from 11 at centromere)
What causes 95% of downs cases
Non-disjunction in meiosis 1 and 2
What is Robertsonian translocation?
Breakage at the centromere at 2 acrocentric chromosomes resulting in 2 with fusion of their long arms to from one derivative chromosome
What is dosage compensation?
equalising the expression of genes between members of different biological sexes, since different numbers of genes but require same amount of gene products
What is turner’s syndrome
X
1 in 3000 live female births
Can be detected in the 2nd trimester, where generalised oedema and swelling in neck can be seen
They can look normal at birth, or have puffy extremities and intra uterine oedema
Low posterior hairline, short 4th metacarpals, webbed neck, aorta defect in 15% of cases
Normal intelligence
In adults, they have short stature and ovarian failure
What is Kleinfelter’s syndrome?
XXY
1 in 1000 live male births: clumsiness, verbal learning disability, taller than average, 30% develop gynaecomastia (breasts), all are infertile, increased risk of leg ulcers, osteoporosis, and breast carcinoma in later life
What is Patau’s
Trisomy 13
Symptoms include: Heart defects, mental retardation
What is Edwards?
Trisomy 18
Symptoms include: heart defects, mental retardation, kidney and digestive tract defects
How can you be phenotypically one sex and chromosomally another sex
Translocation of SRY (Sex determining region) from Y to X
Give 2 examples of a deletion syndrome
Di George syndrome: CongenitalHeartDisease o Palatalabnormalities o Thymic/ParathyroidHypoplasia o CharacteristicFacies o LearningDifficulties
Or Cru-du-crat:
Microcephaly,Hypertelorism,Micrognathia,Epicanthalfolds,Low setears,Hypotonia
Severe psychomotor and mental retardation
Characteristic cat like cry in newborns
Give an example of a duplication syndrome
Charcot-Marie-tooth
Muscle weakness, foot deformities, missing reflexes
What is copy number variant
sections of the genome are repeated and the number of repeats in the genome varies between individuals in the human population
