Molecular and Cytogenetics Flashcards
What protein complexes are associated with the following phases of the cell cycle?
1) S phase
2) G1 phase
3) G2 phase
4) M phase
1) S phase
cyclin E and CDK2
2) G1 phase
cyclin D and CDK4
3) G2 phase
cyclin A and CDK2
4) M phase
cyclin B and CDK1
What molecular alterations occur in the following stages of the adenoma-carcinoma sequence in colorectal cancer?
1) normal epithelium to dysplastic foci
2) early adenoma to intermediate adenoma
3) intermediate adenoma to late adenoma
4) late adenoma to carcinoma
1) normal epithelium to dysplastic foci
loss or mutation of the APC locus on chr 5q
2) early adenoma to intermediate adenoma
mutation of RAS gene on chr 12p
3) intermediate adenoma to late adenoma
loss of tumor suppressor on chr 18q
4) late adenoma to carcinoma
loss of p53 gene on chr 17
What percentage of Down’s is due to a Robertsonian translocation?
4% of DS due to Robertsonian translocation
Mostly der(14;21)
Uniparental disomy (imprinting) of the following chromosomes can result in what disorder?
1) Chr 15
2) Chr 6
3) Chr 11
1) Prader-Willi or Angelman
2) Neonatal diabetes
3) Beckwith-Weideman
*idea behind the imprinting disorders is that you need a copy from each parent of the gene for it to function properly so if you inherit two copies from only one parent, you are going to have disorders
What is the method of PCR?
► Amplifies DNA up to ~35 kb
► Primers, specific design, universal or degenerative
►DNA polymerase enzyme, Mg2+ buffer, dNTPs
► Denature, anneal, extension, repeat ~ 30-35 cycles, yields thousands of copies of original DNA template
Describe the process of sequencing.
► ‘Gold standard’ of DNA testing
► Uses 4 mixes of dNTP’s and dye-attached dideoxy nucleotides (ddATP, ddCTP, ddGTP, ddTTP)
► Each time nucleotide incorporated into chain, if dideoxynucleotide, extension of chain will be terminated
► DNA pulled through capillary by electrophoresis, separated by bases into the ladder patterns
► Ladder ‘read’ automatically using computer algorithm with each base a different color
CYP2D6 affects metabolism of what two drugs?
Codeine to its metabolite morphine
TCAs (ie nortryptyline)
What drugs metabolism is affected by:
1) CYP2C9
2) CYP2C19
3) N-acetyltransferase
1) Warfarin and phenytoin
2) Omeprazole, phenytoin and diazepam
3) N-acetyltransferase is central to the metabolism of isoniazid, some polymorphisms result in increased or decreased activity
What disease is caused by mutations in the COL4A5 gene on Xp22.3 which encodes the alpha 5 chain of type IV collagen and how is it diagnosed on skin or renal biopsy?
Alport’s syndrome
X-linked recessive disorder
Diagnosis by skin or renal biopsies that show absence of IHC staining for alpha5 chain of type IV collagen
What inherited nephrotic syndrome:
caused by mutation of NPHS1 (19q13.1) gene which encodes nephrin which is a key component in the glomerular slit diaphragm
affected children born with markedly enlarged placenta
EM shows abnormal variation in the size of the slit pores and rarefaction of the slit diaphragms
Congenital nephrotic syndrome of the Finnish type
What inherited nephrotic syndrome:
caused by mutation of the LAMB2 (3p21) gene which encodes ß2 laminin which is a component of the glomerular basement membrane
associated with microcoria (fixed narrow pupils), death within several months and renal biopsy shows mesangial sclerosis and crescents
Pierson syndrome
What inherited nephrotic syndrome:
caused by mutation in LMX1B (9q34.1) gene which encodes a transcription factor that regulates transcription of COL4A3
Autosomal dominant disorder with skeletal and ocular anomalies
Renal biopsy shows basement membrane expansion by fibrillary collagen deposits
Nail-patella syndrome
What inherited nephrotic syndrome:
caused by mutation in WT1 gene (11p13)
causes Wilms tumor, male pseudohermaphroditism and rapidly progressive renal failure
Renal biopsy shows mesangial sclerosis
Denys-Drash syndrome
*Frasier syndrome is similar but less severe and is associated with gonadoblastoma
What inherited nephrotic syndrome:
caused by mutation in ACTN4 gene which encodes alpha-actinin or a mutation in TRPC6 gene which encodes transient receptor potential cation channel 6
patients get onset of nephrotic syndrome in adolescence or young adulthood
Familial autosomal dominant focal segmental glomerulosclerosis
What inherited nephrotic syndrome:
caused by mutation in NPHS2 gene which encodes podocin
patients get onset of proteinuria in early childhood
renal biopsy initially resembles minimal change disease but transforms into FSGS
Familial autosomal recessive corticosteroid-resistant nephrotic syndrome
What is an X-linked recessive disorder in the CLCN5 gene encoding a chloride channel that causes proximal tubular dysfunction?
Dent disease
What is the mutation in autosomal recessive PCKD? autosomal dominant PCKD?
PKHD1 gene on chromosome 6p for AR
PKD1 on chromosome 16p13 in 85% for AD
What syndrome has cystic renal dysplasia, polydactyly and occipital encephalocele?
Meckel-Gruber syndrome
What disease is a form of arrhythmogenic right ventricular dysplasia with cutaneous manifestations and woolly hair?
Naxos disease
What is the most common gene mutated in the inherited long QT syndrome?
LQT1 (KCNQ1)
exercise (especially swimming) triggered arrhythmias
What gene is mutated in the form of inherited long QT syndrome that is triggered by auditory stimulus or emotional stimulus and it is the second most common mutated gene in these syndromes?
LQT2 (KCNH2, HERG)
What gene is mutated in the inherited long QT syndrome that is triggered by sleep?
LQT3 (SCN5A)
What gene is mutated in the inherited long QT syndrome that encodes portions of a channel shared with skeletal muscle and it causes Anderson-Tawil syndrome which is a triad of episodic paralysis, long QT interval and dysmorphic features?
LQT7 (KCNJ2)
What gene is mutated in the X linked form of dilated cardiomyopathy? What about the AD form?
X linked: Dystrophin (same as Duchenne and Becker MD)
AD: lots of mutations but most commonly MYH7 gene encoding ß myosin heavy chain
What is the most commonly affected gene in HOCM?
MYH7 (most common mutation R403Q)
Autosomal dominant
What gene is responsible for Holt-Oram syndrome (heart-hand syndrome)?
TBX-5
AD disorder with heart and upper limb abnormalities
Heart defects are usually septal defects
What syndrome is caused by a PTPN11 mutation and consists of right sided heart defects, most commonly pulmonic stenosis and HOCM is the 2nd most common finding, lymphatic malformations are also common?
Noonan syndrome
What is the mutation in Alagille syndrome and what is this syndrome?
JAG1
AD condition causing paucity of bile ducts but it also causing disease of blood vessels and the heart and most commonly affects pulmonary circulation in the form of pulmonary artery stenosis
What gene is responsible for the cardiac anomalies seen in DiGeorge syndrome?
TBX1
What syndrome is due to deletion of the elasin gene and has a characteristic supravalvular aortic stenosis (hourglass stenosis)?
Willams syndrome
DEFINITE BOARD Q!!!
Be able to interpret a gel from a patient with Fragile X!!
Here is an example gel–lane 7 is pt with FragX
Fragile X syndrome is associated with the expansion of the CGG trinucleotide repeat affecting the Fragile X mental retardation 1 (FMR1) gene on the X chromosome, resulting in a failure to express the fragile X mental retardation protein (FMRP), which is required for normal neural development. Depending on the length of the CGG repeat, an allele may be classified as normal (unaffected by the syndrome), a premutation (at risk of fragile X associated disorders), or full mutation (usually affected by the syndrome)
