Genetics Flashcards
25 year old with primary amenorrhoea, normal secondary sex characteristics, uterine & cervical aplasia. What is the genetic picture?
Primary amenorrhea with absent uterus, vagina ends in a blind pouch, normal breasts and scant pubic hair is seen with bilateral hernia
Mayer Rokitanski Kusher Hauser Syndrome
(booklet says this)
bilateral hernia = Androgen insensitivity syndrome
At what number of weeks can CVS and amniocentesis be done?
CVS - from 11/40
Amniocentesis - from 15/40
What is the inheritance of Achondroplasia
Autosomal dominant
Diagnostic test for cystic fibrosis in blood
Chromosomal analysis
Which test increases the number of copies of DNA?
PCR
Quadruple test postive means
AFP decreased
Unconjugated E3 decreased
Bhcg increased
Inhibin A increased
What hormone is deficient in congenital adrenal hyperplasia?
21 hydroxylase deficiency
Cortisol and androgen deficiency
What are the findings on Down’s syndrome screening
AFP decreased
Unconjugated E3 decreased
Bhcg increased
Inhibin A increased
Complete mole karyotype
46XX
Mother and father homozygous for sickle cell: effect on children
Sickle cell
Duchenne muscular dystrophy mode of inheritance
X linked recessive
Sickle cell disease mode of inheritance
Autosomal recessive homozygous
Trisomy 18 condition name
Edwards
Partial mole genome
69 xxy
Triploidy
46 of paternal origin
23 of maternal origin
Confined placental mosaicism
Abnormalities in the placental but not foetal tissues
Mode of inheritance of Hungtons chorea
Autosomal dominant
Mode of inheritance of Von willebrand
autosomal recessive
mitochondrial chromosomes - inheritance
Inherited maternally only
What is the 2nd common enzymatic deficiency after 21-OH CAH ?
11 beta-hydoxylase deficiency
karyotype graph (47, XXY). What is the diagnosis ?
Klinefelters
How many genes encoded in mitochondrial DNA?
37 genes
Father has cystic fibrosis (rr), and the mother is normal (RR). What is the probability of having an affected child?
0%
What is the name of a chromosome rearrangement that involves the transfer of genetic material between two non-homologous chromosomes?
Translocation
(reciprocal or robertsonian?)
What is the difference between Robertsonian translocation and Reciprocal translocation?
Translocations:
Reciprocal - exchange segments of chromosome
Robertsonian - entire chromosome attaches to another at the centromere
Does balanced translocation impact the genetic material quantity?
No loss of genetic material
Does UN-blanaced translocation impact the genetic material quantity?
Increase of genetic material
USS image ‘bunch of grapes’
What is the diagnosis and karyotype?
Complete mole
46 XX
(NOT 46 XY)
Trisomy 13
Patau
Pedigree diagram:
Carrier mother
Unaffected father
Affected son
Mode of inheritance?
X linked recessive
A woman is a carrier of CF and her partner is Caucasian with a rate of 1/25. What is the risk of the child having cystic fibrosis?
1%
(1 in 4) x (1 in 25)
4x25 = 100
1 in 100 = 1%
?????
Infertility case, Male 190 cm wt 60 kg, testicular volume 5 ml. What is the possible karyotype?
47XXY
Rate of miscarriage in couples with balanced translocation?
2-5%?
Case of a male with azoospermia and loss of smell (anosmia) diagnosis?
Kallman’s Syndrome
(hypogonadotrophic hypogonadism)
Edwards syndrome in a male patient
46 or 47
XX or XY
47XY
Trisomy 18
Interpretation of downs screening results
Age related risk; 1:1000MoM
AFP; 1.05MoM
β-hCG; 0.85
Test risk; 1:10000
Low risk for downs
A woman is 8 weeks pregnant attends for genetic counseling as she worried about CF, her sister has a child with cystic fibrosis. She is a carrier and her partner is normal What is the risk of the child having cystic fibrosis?
0%
Autosomal recessive
Rr
+
RR
= no chance of rr
Mother has sickle cell disease married to sickle cell trait husband chance of baby to having disease?
50%
Autosomal recessive
rr
+
Rr
= Rr/Rr/rr/rr
Which chromosomes are capable of robertsonian translocations?
13, 14, 15, 21, 22
Woman has a stillbirth (trisomy 13). Finds out she has a balanced translocation 13/14. What is the chance of having live baby with unbalanced translocation?
50%
1/4 - normal
1/4 - balanced
2/4 - unbalanced
Primary amenorrhea, short stature, webbed neck
Turners
Azoospermia, height 1.9m, small testes
Klinefelters
Karyotype 46 XX, absent uterus
Rokitansky
What is the mode of inheritance of BRCA1/2
Autosomal dominant
What is the pattern of hormones in Klinefelter’s ?
Testosterone
SHBG
FSH/LH
Testosterone low
SHBG high
FSH/LH high
Which two trisomies can be caused by robertsonian translocation?
Downs (21) and patau (13)
Most common mutation in Lynch snydrome
MLH1 ?
Think ‘L’ for Lynch
(less so MSH2)
What is the risk of [‘accidental’] abortion associated with amniocentesis?
1%
Which arm of the Y chromosome has the sex determining gene on it?
The short arm of the Y chromosome
What is the karyotype of Edwards?
47XX +18
47XY +18
What DNA band is stained during karyotyping
G banding
Bilateral renal agenesis –>
Oligohydramnios –>
Compression: limb hypoplasia, low ears
Potter’s syndrome
What ~DNA issue causes Lynch syndrome
mutation of genes involved in DNA mismatch repair
