Genetics Flashcards
Karyotype for Turners
XO
Karyotype for Edwards Syndrome
Trisomy 18
Karyotype for Klinefelter syndrome
XXY
Genetic defect in Noonan’s syndrome
Defect in the Ras/MAPK signaling pathway
Genetic Inheritance of Huntington’s Disease
Autosomal Dominant
CAG triplet repeats on chromosome 4
Index cases can occur due to a de novo mutation or due to anticipation
Kleinfelter hormone findings + clinical manifestations
High FSH and LH, low testosterone
Small penis and balls
Risk of DM, CVD, cancer
In what clinical situation is the CGH microarray most useful for?
Chromosomal microdeletion
What is the mechanism of somatic chromosomal translocation in causing cancer?
Gene fusion
Duchenne MD gene mutation
Multi exon deletion
X chromosome linked
Tuberous sclerosis
Low intelligence
Epilepsy
Adenine sebacium
Autosomal dominant
DiGeorge
CATCH22 Chromosome 22 deletion Cardiac defect tetralogy fallout Abnormal facies Thymic aplastic with infections Cleft palates Hypocalcaemia
Purines
Adenine
Guarnine
2 ring structure
Pyramidines
Cytosine
Uracil (RNA)
Thymine (DNA)
Single ring structure
What happens during G2 phase of the cell cycle
Cell is preparing for mitosis
Microtubule productin
What happens during G1 phase of the cell cycle
The cell grows and synthesid of mRNA and proteins including histones. The volume of the cytoplasm is increased
What happens during S phase of the cell cycle
DNA synthesis
Chromosome duplication
What does telemorase ribonucleoprotein do?
Adds base pairs to DNA to cap the DNA
interfering mRNAs (micro-RNAs) action
mRNA degradation
Missense mutation
A substitution in one DNA base pair that changes the codon for one amino acid to the codon for another amino acid
Nonsense mutation
A substituation of a DNA base that changes a codon to a stop codon
Splice site mutation
Intron or exon exon deletion
frameshift mutation
deletion of 1 nucleotide within 1 exon
Mutation seen in Duchenne muscular dystrophy
Deletion of multiple exons (splicing)
PARP-1 action
required for base excision repair (BER)
Mechanism of somatic chromosomal translocation in causing cancer?
Gene fusion
Examples of alleilic heterogeneity
Same gene location
Different allele mutations
Same Disease
CF
MEN
Examples of Locus (non-allelic) heterogeneity
Different genes
Same Disease
BRCA-1/2 HOCM Familial hypercholesterolaemia Ehndler-Danlos Retinitis Pigmentosum
Transmission of mitochondrial mutation
Heteroplasmy with mitochondrial inheritence (from mother with all children affected)
Barr body
Inactivated X chromosome due to lyonisation
Pleiotropy
One mutation affecting multiple organs
e.g. CTFR in CF
Epistasis
One gene impacts on the expression of others
e.g. albinism
Gene mutation in Fragile X
CGG repeats leading to silencing of FMR-1 gene
X-linked dominant pattern
Features of fragile X
Long narrow face Large ears prominent jaw Enlarged testicles Mental retardation
Genetics of prader-willi syndrome
Disruption or deletion of genes in chromosome 15
Clinical features of prader willi-syndrome
Small statue Small hands and feet Central obesity Intellectual disability Characteristic behaviours
Type of mutation leading to a proto-oncogene
Missense
Tays-Sachs mutation
Frameshift muation
In frame deletion
Deletion of 3 base pairs
Linkage disequilibrium
Non-random associations between polymorphisms at different loci
Marfan’s gene
FBN-1 gene
Noonan’s syndrome clinical
Autosomal dominant Short stature Variable intellectual disability Pulmonary stenosis (also HOCM, ASD, VSD)
Treatment of AF in HOCM
Anticoagulate (warfarin) despite CHADVASC
When to avoid stress ECG/Echo
LBBB
Heart block in which atropine should not be used
Mobitz type 2
Fabry disease
GL-3 ubiquitous accumulation X Linked recessive GI symptoms Kidney failure Cardiac hypertrophy, arrhythmia, valvulopathy Peripheral neuropathy Stroke
Still’s disease
Fever Arthralgia Salmon-rash LN Organomegaly
Li-Fraumeni Disease
Autosomal dominant
p53 suppressor gene mutation
Cancers at ~25yo
sarcomas, breast, leukaemia
Peutz jager disease
Autosomal dominant STK11 gene Harmatomous polyps GIT Pigmented macules (lips) Risk of Ca GIT, pancreas, breast, ovary
Neurofibromatosis 1
Autosomal dominant
NF-1 gene for neurofibromin
Cafe-aut-lait spots Lisch nodules Cognitive impairment Neurofibromas Bony lesion
Neurofibromatosis 2
bilateral acoustic schwannomas and meningiomas
No lisch nodules
Schwannomas
Less cognitive impairment
Tuberous Sclerosis
Autosomal dominat
TSC1 - hamartic
TSC2 - tuberin
Skin - hypopigmented lesion, angiofibromas, shagreen patched
Tumours- brain, heart (rhabdomyoma), skin, eyes, kidney (angiomyolipomas), lung, and liver.
Charcot-Marie-Toot disease
Autosomal dominal PMP-22 gene coding for myelin
Peripheral motor and sensory neruopathy
Myotonic dystrophy
Autosomal dominant
T1: DMPL genge
Type 2: CNBP gene
Myotonia Characteristic facies - hatchet facies Fatigue Cataracts Cardaic abnormalities
Tay-Sachs disease
Autosomal recessive
Lysosomal storage disorder - HEXA gene
Neurodegenerative disorder, children die at 4
Duchenne/Becker Muscular dystropy
X Linked Recessive
Dystrophin gene
Intellectual disability
Heart failure
Muscle and respiratory weakness
Freidrich’s ataxia
Autosomal recessive Mitochondrial dysfunction (GAA triplet repeat)
Ataxia
HOCM
Diabetes
Alport syndrome
X Linked dominant
Type 4 collagen - ears, lens, kidney issues
Rett syndrome
X Linked Dominant- MECP2
Affects brain development in girls
