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Genetics Flashcards

1
Q

What phase of cell cycle do chromosomes condense enough for karyotyping

A

metaphase

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2
Q

Haploinsufficiency

A

Reduction by about half in amount of protein usually due to whole gene deletion or frameshift mutation

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3
Q

Silent mutation

A

changes that don’t affect the A.A produced by the codon

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4
Q

Missense mutation

A

Change that affects the A.A produced by the codon

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5
Q

Nonsense mutation

A

Change that results in a stop codon

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6
Q

Frameshift mutation

A

Alters the reading frame, may lead to entirely different protein or a stop codon

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7
Q

Locus

A

The location of a gene on a chromosome

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8
Q

Allele

A

an Alternative variant of a particular gene

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9
Q

Polymorphism

A

where there are at least 2 or more relatively common alleles of a gene in a the population

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10
Q

Penetrance

A

on/off binary concept
Expressed or not expressed
Incomplete penetrance: may be age dependent like in huntington’s

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11
Q

Expressivity

A

Variability of clinical features/phenotype in people with the same genotype

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12
Q

Aneuploidy

A

an abnormal number of chromosomes

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13
Q

47 XXY condition and presentation

A

Klinefelter Syn

  • Primary hypogonadism
  • Low testosterone
  • Infertility, incomplete virlisation, gynecomastia
  • tall stature
  • mild learning difficulty, shy, emotionally immature
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14
Q

45 X condition and presentation

A

Turner Syn

  • Short stature, shield chest
  • Webbed neck
  • Infertility, ovarian dysgenesis
  • Bicuspid Aortic valve, CoA
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15
Q

Inheritance of myotonic dystrophy

A

Triplet repeat disorder

-Maternal

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16
Q

Inheritance of huntington’s

A

Triplet repeat disorder

-Paternal

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17
Q

Inheritance of Spinocerebellar ataxia

A

Triplet repeat disorder

-Gender of transmitting parent can modify symptoms in child

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18
Q

Anticipation

A

The observation that a particular phenotype seems to be increasing in severity in subsequent generations

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19
Q

CpG islands

A

on promoter regions of genes and is the mechanism of regulating gene transcription

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20
Q

ncRNA

A

Non coding RNA

-Does not code for protein, but mediates gene regulation processes

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21
Q

What is gene expression influenced by

A

conformation of chromatin
methylation of DNA
Availability of transcription factors

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22
Q

Inheritance of Prader-Willi

A

Loss of paternally active 15q gene copy

  • Paternal imprinting
  • Paternal microdeletion
  • Maternal UPD15
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23
Q

Inheritance of Angelman Syndrome

A

Loss of maternallly active 15q gene copy

  • Maternal imprinting
  • Maternal microdeletion
  • Paternal UPD15
  • UBE3A mutaton
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24
Q

RB1 -Condition and inheritance

A

AD
Retinoblastoma

Other features:
-melanoma
Osteosarcoma
Soft tissue cancers

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25
Q

Most familial cancers are due to germ line mutations in tumor suppressor genes rather than proto-onogenes except:

A

RET gene mutation - MEN 2

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26
Q

MENIN gene

A

MEN 1

AD inheritance

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27
Q

Features of MEN 1

A

Parathyroid adenoma
Pituitary adenoma
Pancreatic islet cell/GI adenoma

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28
Q

RET gene

A

MEN2

AD inheritance

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29
Q

MEN2a features

A

Medullary thyroid cancer
Phaochromocytoma
Parathyroid hyperplasia

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30
Q

MEN2b features

A

Medullary Thyroid cancer
Phaeochromocytoma
Neuromas/fibromas + marfanoid features

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31
Q

Inheritance of BRCA mutation

A

AD, highly penetrant

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32
Q

TP53 gene mutation

A

Li Fraumeni syndrome

AD inheritance

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33
Q

Li Fraumeni syndrome features

A

SBLA
-Sarcoma, Breast, leukemia, adrenal gland cancers

Very young onset usually (before 30 yo)

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34
Q

Role of p53 in cancer

A

Tumor suppressor gene
If DNA is damaged, p53 prevents malignant transformation by delaying cell cycle progression
-Allows cell to initiate DNA repair or can initiate apoptosis

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35
Q

PTEN gene mutation

A

Cowden Syndrome

AD inheritance

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36
Q

Features of Cowden syndrome

A

Breast cancer and Skin changes

Papillary thyroid cancer

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37
Q

APC gene mutation

A

FAP

AD inheritance

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38
Q

MutYH gene mutation

A

MutYH associated Polyposis

  • Phenotypically similar to FAP
  • AR inheritance - so may look like de novo FAP
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39
Q

STK11 gene mutation

A

Peutz Jegher Syndrome

AD inheritance

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40
Q

Features of Peutz Jegher Syndrome

A
  • Hamartomatous polyposis ( low malignant potential)
  • Lip, buccal, palm pigmentation
  • Risk of intussussception/volvulus
  • Increased risk of GI and breast cancer
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41
Q

MMR gene mutations in Lynch Syndrome

A

MLH1, MSH2, MSH6, PMS2, EPCAM

42
Q

Amsterdam criteria for Lynch syndrome

A

3 or more affected relatives w/ CRC
2 or more generations affected
1 or more <50 yo a diagnosis

FAP excluded

43
Q

How to test for MMR mutations

A
  1. MSI testing
  2. Immunohistochemistry - absent staining seen if defect
  3. Germ line testing
44
Q

SDHB gene mutation

A

paragangliomas and phaeochromocytoma

45
Q

Neurofibromin 1 gene mutation

A

neurofibromatoisis type 1

AD inheritance

46
Q

Neurofibromatoisis type 1 Features

A 
2 or more of:
Cafe au lait spots
Neurofibroma/plexiform neurofibroma
Axillary freckling
Lisch modules on irus
Optic glioma
1st degree relative w/ NF
47
Q

Merlin gene mutation

A

neurofibromatoisis type 2

AD inheritance

48
Q

Neurofibromatoisis type 2 Features

A 
Bilateral acoustic schwannoma by age 30 usually
Meningioma/Neurofibroma/Swannoma/Glioma
Polyneuropathy
Cataracts
Cutaneous tumors/plaques
49
Q

VHL gene mutation

A

Von Hippel Lindau Disease

50
Q

Von Hippel Lindau Disease Features

A

Clear cell renal cancer
Neurological/retinal haemangioblastoma
Phaeochromocytoma

51
Q

Compound heterozygote

A

Different mutations in each pair of a gene

52
Q

Allelic heterogeneity

A

The same phenotype can be caused by more than one mutation in a gene (e.g CF)

53
Q

Locus heterogeneity

A

The same phenotype can be caused by mutations in more than one gene (e.g. tuberous sclerosis)

54
Q

Inheritance of Marfans

A

AD

55
Q

Inheritance of Tuberous sclerosis

A

AD

56
Q

Inheritance of vWD

A

AD

57
Q

Inheritance of Noonan Syndrome

A

AD

58
Q

Inheritance of Hereditary hemorrhagic telangiectasia

A

AD

59
Q

Inheritance of acute intermittent porphyria

A

AD

60
Q

Inheritance of Wilsons Disease

A

AR

61
Q

Inheritance of Friedrich Ataxia

A

AR, trinucleotide repeat disorder

62
Q

Inheritance of Haemochromatosis

A

AR

63
Q

Inheritance of Alpha 1 antitrypsin

A

AR

64
Q

Inheritance of Phenylketonuria

A

AR

65
Q

Equation for incidence of a recessive condition

A

Incidence = (Carrier Freq^2) x4

66
Q

Equation for carrier frequency of a recessive condition

A

Carrier frequency = square root of (incidence/4)

67
Q

Inheritance of G6PD deficiency

A

X linked

68
Q

Inheritance of Fabry Disease

A

X linked

69
Q

Inheritance of Chronic granulomatous disease

A

X linked

70
Q

Inheritance of Duchenne muscular dystrophy

A

X linked

71
Q

Inheritance of Rett syndrome

A

X linked - Dominant

72
Q

Inheritance of Fragile X syndrome

A

Triplet repeat disorder on X chromosome

-Worse when maternally transmitted

73
Q

Heteroplasmy

A

Some mitochondria have a mutation and others don’t

74
Q

When can CVS be performed

A

11-15 weeks
Needle into placenta
1:500 miscarriage risk

75
Q

Role for NIPT

A

Can be done at 10+ weeks
Assesses for aneuploidy, deletion syndromes, gender
-Fragments of placental DNA extracted from maternal blood

76
Q

CACNA1A gene mutation

A

Torticollis

77
Q

Features of tuberous sclerosis

A 
Ungal/periungal fibroma
Ash leaf macules
Facial angiomas/forehead plaques
Shagreen patch
Retinal nodular hamartomas
Brain - nodules/tubers/astrocytoma - Seizures and ID
Renal angiomyolipoma/cysts
Cardiac rhabdomyoma
LAM - lungs
78
Q

Tx option in Tuberous sclerosis

A

mTOR inhibitors

79
Q

FMR1 gene mutation

A

Fragile X

-CGG repeat

80
Q

Features of Friedrich Ataxia

A

Cerebellum and dorsal root ganglia affected
-Gait and limb ataxia
HOCM
Diabetes

GAA repeat in FXN gene

81
Q

Abnormal Dystrophin gene

A

Becker muscular dystrophy

-Deletion/mutation is inframe resulting in a shortened semi functional protein/milder phenotype

82
Q

Absent Dystrophin gene due to deletion usually

A

DMD

-Deletion/mutation disrupts the reading frame and therefore no functional protein

83
Q

DMD features

A 
Delayed motor milestones
Broad waddling gait, falls
Gower sign - trouble with stairs
Calf pseudohypertrophy (muscle replaced with connective tissue/fat)
Cardiomyopathy
Mild ID
Life expectancy 20s
84
Q

Trisomy 21 features

A 
ID
Hypotonia
Hearing/Vision
Alz disease
Congenital heart disease: VSD>endocardial cushion defect>PDA>ASD>TOF
Hypothyroid
Leukemia
OSA
85
Q

Fragile X features

A 
ID, behavioral proglems
Seizures
Mitral Valve prolapse
PRemature ovarian failure
FXTAS
86
Q

Karyotype

A

For detection of:

  • Aneuploidy
  • Balanced translocation (location of gene)
87
Q

FISH (Fluorescence in situ hybridisation)

A

Assess for presence of absence of particular DNA sequences on chromosomes
-Balanced rearrangements

88
Q

CGH microarray

A

Assess gains/loss of DNA content

  • For unbalanced changes
  • Can detect: microdeletions/duplications and monosomies and trisomies

NOT for Balanced changes

89
Q

SNP Array

A 
For copy number neutral variation with genotype abnormalities
Allelic imbalance (uniparental disomy, chimerism)

+what CGH microarray does

90
Q

Sanger Sequencing

A

For single gene mutations

-Cannot detect deletions/duplications

91
Q

Single gene sequencing

A

looks at a particular area of interest and gives precise DNA sequencing of targeted gene
-For changes of a single base within a gene

92
Q

Southern blot

A

For Trinucleotide repeat disorders

Looks at DNA

93
Q

Western Blot

A

Can be used to look for proteins in trinucleotide repeat disorders like with DMD

94
Q

Whole genome sequencing

A

o Detects genes and will inform you if there are sequence abnormalities in the gene, but cannot tell you location of the gene or if genes are missing or added
o Helpful for heterogenous conditions (e.g. epilepsy)
o Not good for triplet repeat disorders and deletions

95
Q

miRNA

A

Post transcriptional regulator that binds to complementary sequences in mRNA

96
Q

siRNA

A

Small interfering/silencing RNA

Knock down their target RNA

97
Q

Digenic mutation

A

Two mutations in 2 different genes that code for different proteins that are often structurally or functionally related that lead to a phenotype/disease

98
Q

Wolfram Syndrome

A

DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness)

AR

Gene: WFS1

99
Q

MELAS

A

mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes

Mitochondrial disease

Stroke like presentation
Seizures
Hearing loss
Muscle weakness
Migraines
100
Q

CADASIL

A

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

NOTCH3 gene mutation on Chromosome 19

CAuse of stroke in young
TIA like Sx and small vessel ischemic strokes

Bpt (15 decks)

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