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BPT Written > Genetics > Flashcards

Genetics Flashcards

1
Q

Genetic abnormality that most commonly caused Downs Syndrome?

A

Nondisjunction = error in cell division where the chromosomes fail to separate during cell division. Meiotic disjunction will result in the gamete carrying this abnormality and further resulting in trisomy 21

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2
Q

COL4A5 gene

A

X-linked transmission in Alport Syndrome

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3
Q

UMOD gene

A

Autosomal dominant tubulointerstitial kidney disease (ADTKD)

ADTKD due to UMOD mutations characterised by gout occurring at an early age

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4
Q

HNF1B

A

Hepatocyte nuclear factor 1 beta
ADTKD due to HNF1B - renal cysts, maturity onset diabetes of youth, hyperuricemia, hypomagnesemia, deranged LFTs and renal anomalies

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5
Q

MUC1

A 
Mutation causes subtype of ADTKD
Progressive CKD (no cysts)
Autosomal dominant
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6
Q

Fabry disease

A

X-linked disorder
Little or no functional alpha-Gal A enzyme activity
- severe neuropathic or limb pain
- telangiectasias and angiokeratomas (hip, groin, periumbilical)
- GI symptoms: abdo pain, N / V / D
- Corneal opacities
- Renal manifestations e.g. proteinuria
- Cardiac: LVH, myocardial fibrosis, heart failure, valve abnormalities
- TIA / stroke

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7
Q

BMPR2

A

Bone morphogenic protein receptor

Common in heritable pulmonary arterial hypertension

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8
Q

Robertsonian translocation

A

Translocation between 2 acrocentric chromosomes (13, 14, 15, 21, 22)

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9
Q

Klinefelter Syndrome

A

47, XXY
Most common cause of primary male hypogonadism
Low testosterone
Infertility, incomplete virilisation, gynecomastia
Tall
Learning difficulties, emotionally immature, shy

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10
Q

Turner Syndrome

A

45,X - don’t have 2 X chromosome in female
Web neck
Ovarian dysgenesis, infertility
Cardiovascular defects: bicuspid aortic valve, coarctation of the aorta
Normal intellect

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11
Q

Autosomal dominant

A

Disease results from mutation in one copy of gene / allele (heterozygous)
If one parent has the disease, 50% chance child inherits the gene
E.g. NF; Marfans

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12
Q

Autosomal recessive

A

Disease results from mutation in both copies of gene / allele (homozygotes)
If both parents are carriers, 25% chance child inherits 2 copies of the gene
E.g. CF, Thalassa is

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13
Q

X linked recessive

A

Absence of father-son transmission
Affected males much more common
Females rarely affected

E.g. Haemophilia A, duchenne muscular dystrophy, colour blindness, adrenoleukodystrophy, Fragile X

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14
Q

Methylation

A

Promoter regions are CpG rich

IF methylated the promoter region = turn off the gene (transcriptional silencing)

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15
Q

Gene expression is influenced by?

A

Conformation of chromatin
Methylation of DNA
Availability of transcription factors

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16
Q

Imprinting

A

Involves parental specific methylation of CpG-rich domains and modification of of his tone proteins
Is the epigenetic marking of a gene based on its parental origin and results in monoalleic expression
Maternal imprinting = maternal silencing, paternal gene expression

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17
Q

Prader-Willi Syndrome

A

Imprinting disorder - loss of the paternally active 15q gene copy

Hypotonia, hyperphagia, obesity, short stature, moderate ID, hypogonadism

18
Q

Angleman Syndrome

A 
Loss of maternally active 15q gene copy
Paternal uniparental disomy 
Imprinting defect (q12)
Large deletion on maternally inherited chromosome 15
Angleman Gene = UBE38

Severe intellectual disability, unsteady gait, epilepsy

19
Q

FISH

A

Fluorescent tagged DNA probes for specific target
Detect presence/absence of specific DNA sequences on Chromosomes
Locus specific
Requires locus specific hypothesis
Takes 24 hours
E.g. trisomy

20
Q

Next-generation sequencing

A

DNA sequencing of whole genome / exome
Analyse multiple genes simultaneously
Cannot detect triple repeats or methylation defects

21
Q

Pharmacogenetics - Warfarin

A

Cytochrome P450 (CYP2C9)

22
Q

Pharmacogenetics - Tamoxifen

A

Cytochrome P450 (CYP2D6)

23
Q

Karyotype

A

Visually analyses whole chromosomes
Detects aneuploidy, large chromosomal imbalances and unbalanced translocations
Cells arrested in metaphase - chromosomes stained
Takes 10 days
E.g. looking at world from outer space…New Zealander has disappeared (e.g. Turner syndrome)

24
Q

Comparative Genomic Hybridization

A

Compare DNA from two sources (test and control)
Looks at gains / losses of DNA; also looks at copy numbers variations
I.e. Google earth map is a jigsaw puzzle- see if any pieces are missing or duplicated
E.g. Trisomy 21, 22q11

25
Q

Single nucleotide polymorphism array

A

Variation in a single nucleotide at a specific locus
Can detect copy number abnormalities (microdeletions / microduplications), allelic imbalance
E.g. loss of heterozygosity e.g. uniparental disomy in Angelman
Mutated copy of tumor suppressor gene in cancer
MAY get results of unknown significance

26
Q

Sanger sequence

A

Exact DNA sequence of bases of a gene
Can detect single gene mutations
E.g. Noonan (PTPN11), NF1, Marfan (FBN1)

27
Q

PCR

A

Used for amplification of sequence of interest
Heat dsDNA - separates strands
Oligonucleotide primer binds to start of DNA sequence of interest
Primer helps the DNA polymerase get started
Polymerase reads down the DNA sequence - adds complementary base pairs to form complementary sequence

28
Q

Triple repeat disorders

A 
Fragile X - CGG
Huntington Disease - CAG
Spinocerebellar Ataxia - CAG
Friedrich Ataxia - GAA
Myotonic Dystrophy - CTG
29
Q

Multiplex Ligation-dependent Probe Amplification

A

Gene exon
Locus specific hypothesis
Modified PCR amplification
Each amplification product has a unique length
Amplification products separated by electrophoresis
Reflects the relative copy number of target sequences
Tests for deletions and duplications of any gene

30
Q

Li Fraumeni Syndrome

A 
SBLA: Sarcoma, Breast (HER2 positive),Leukaemia, Adrenal gland
TP53 - tumor suppressor gene
Inherited autosomal dominant disorder
Cancer diagnosis at a young age
Highly penetrant
31
Q

Cowden Syndrome

A

PTEN (phosphate and tensin homologous) tumor suppressor gene
Autosomal dominant inheritance of a germ line mutation
Breast cancer, bending breast changes, endometrial and follicular thyroid cancer, microcephaly

32
Q

Von Hippel Lindau Disease

A

VHL tumor suppressor gene
Clear cell renal cancer
Sequale from neuro or retinal haemangioblastoma
Phaeochromocytoma

33
Q

Neurofibromatosis Type 1

A 
Requires two or more of:
>6 cafe au lait patches
>2 neurofibromas OR 1 plexiform neurofibroma
Axillary and / or inguinal freckling
>2 Lisch nodules on iris
Optic glioma 
Tibial pseudo arthritis 
1sr degree relative with NF

Gene: Neurofibromin 1 (AD)
Highly variable phenotype
Autosomal dominant

34
Q

Neurofibromatosis Type 2

A 
Bilateral acoustic schwannoma
Intracranial and spinal Timor’s: meningioma, neurofibromas, Schwannoma, Glioma
Polyneuropathy
Cataracts
Cutaneous tumors and plaques

Genetics: mutation in NF2 gene (codes for Merlin) Autosomal Dominant

35
Q

Beckwith Wideman Syndrome

A 
Loss of maternal 11p15 gene
Overgrowth disorder 
Macrosomia
Macgroglossia
Embryonal malignancies
36
Q

Russell Silver Syndrome

A

Loss of paternal 11p15 genes
Short stature
IUGR
Triangular face

37
Q

Tuberous Sclerosis

A

Autosomal dominant
Abnormal TSC 1 or 2 (tumor suppressor gene)
Multiple benign hamartomas of multiple organs
Skin: hypopigmented lesions, facial angiofibroma, shagreen patches, forehead fibrous plaques
Brain: seizures, ID, tubers, subependymal nodules
Kidney: renal angiomyolipotomata
Heart: cardiac rhabdomyomas

Rx: mTOR inhibitors (mTOR activated by mutations in TSC1 and 2)

38
Q

Friedrich Ataxia

A

Autosomal dominant
Progressive neurological dysfunction: cerebellum & dorsal root ganglia
Absent lower limb reflexes, up going planters
Posterior column dysfunction
Hypertrophic cardiomyopathy, Diabetes

39
Q

Duchenne Muscular Dystrophy

A

Deletion / mutation disrupts the reading frame = no functional protein (dystrophin)
Proximal muscle weakness - Gower sign, calf pseudohypertrophy
Dystrophin also in heart/brain = cardiomyopathy; IQ impairment

Becker muscular dystrophy = deletion / mutation is ‘in frame’ resulting in a shortened semi-functional protein / milder phenotype

40
Q

Marfans

A 
Diagnosis in absence of FHx
Aortic root enlargement and 1 of the following 
- ectopica lentils
- pathogenic FBN1 variant
- Systemic score >7
41
Q

Homoplasmy

A

All of the mitochondrial DNA is affected

42
Q

Achondroplasia

A

Autosomal dominant disorder associated with short stature
Mutation in Fibroblast Growth Factor Receptor 3 (FGFR-3) gene
Short limbs, short fingers
Large head with frontal bossing
Midface hypoplasia with a flattened nasal bridge

BPT Written (16 decks)

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