1 congenital defects

Question 1

What is a deformation?

Answer 1

“distortion of a structure by mechanical force, e.g. club foot

Question 2

What is a dysplasia?

Answer 2

“abnormal organization of tissue e.g. thanatophoric dysplasia”

Question 3

What is a malformation?

Answer 3

“primary structural defect, e.g. cleft lip”

.

Question 4

What is a disruption?

Answer 4

“extrinsic factor affecting normal development, e.g. digital amputation
”

.

Question 5

What is a syndrome?

Answer 5

“consistent pattern of abnormalities, e.g. Down’s syndrome

”

Question 6

What is a sequence?

Answer 6

“multiple abnormalities initiated by primary factor, e.g. Potter’s sequence”

Question 7

What is an association?

Answer 7

“– non-random occurrence of clinical features not explained by sequence or syndrome, e.g. VATER syndrome”

Question 8

What is a dismorphism?

Answer 8

“unusual or abnormal physical feature (sometimes as part of a genetic syndrome), e.g. hypertelorism
”

Question 9

Name common aneuploidies?

Answer 9

“21 (Down syndrome)
Trisomy 18 (Edwards’ syndrome)
Trisomy 13 (Patau syndrome)
Monosomy X (Turner’s syndrome)
XXY (Klinefelter’s Syndrome)
XYY  and XXX
”

Question 10

What are the 7 abnormalities?

Answer 10

Deformation
Dysplasia
Malformation
Disruption
Sequence
Syndrome
Association
Dimorphism

Question 11

3 types of chromosomal abnormalities?

Answer 11

Numerical–aneuploidy–lossofgainofachromosome

Structural–translocations,deletions,insertions,inversions,rings o Mosaicism– different cell lines

Question 12

What are the common symptoms of down’s syndrome

Answer 12

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

Question 13

How common are congenital abnormalities

Answer 13

1 in 50 births

Question 14

What does reduced amniotic fluid lead to

Answer 14

Potter’s sequence

Question 15

How does the centromere determine the type of chromosome

Answer 15

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

Question 16

Give a stain used for karyotypes

Answer 16

Giesma

Question 17

How is the chromosome band written

Answer 17

Chromosome number
P or Q arm
Band number ( up from 11 at centromere)

Question 18

What causes 95% of downs cases

Answer 18

Non-disjunction in meiosis 1 and 2

Question 19

What is Robertsonian translocation?

Answer 19

Breakage at the centromere at 2 acrocentric chromosomes resulting in 2 with fusion of their long arms to from one derivative chromosome

Question 20

What is dosage compensation?

Answer 20

equalising the expression of genes between members of different biological sexes, since different numbers of genes but require same amount of gene products

Question 21

What is turner’s syndrome

Answer 21

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

Question 22

What is Kleinfelter’s syndrome?

Answer 22

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

Question 23

What is Patau’s

Answer 23

Trisomy 13

Symptoms include: Heart defects, mental retardation

Question 24

What is Edwards?

Answer 24

Trisomy 18

Symptoms include: heart defects, mental retardation, kidney and digestive tract defects

Question 25

How can you be phenotypically one sex and chromosomally another sex

Answer 25

Translocation of SRY (Sex determining region) from Y to X

Question 26

Give 2 examples of a deletion syndrome

Answer 26

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

Question 27

Give an example of a duplication syndrome

Answer 27

Charcot-Marie-tooth

Muscle weakness, foot deformities, missing reflexes

Question 28

What is copy number variant

Answer 28

sections of the genome are repeated and the number of repeats in the genome varies between individuals in the human population