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Genetics > Med foundations 1 > Flashcards

Med foundations 1 Flashcards

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1
Q

Constitutional/Congenital

A

Present at birth

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2
Q

Pathogenetic (definition)

A

Genetic alteration causing disease

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3
Q

Obligate Carrier (define)

A

Parent of a child with a recessive condition

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4
Q

Mosaic (define)

A

Two or more cell lines in one person

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5
Q

Chimera (define)

A

Mix of two cell lines, think of bone marrow transplant

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6
Q

Consanguinity

A

Individuals descended from common ancestor; second cousin or closer. .2% of US

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7
Q

Acquired

A

somatic change after birth, usually cancer related

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8
Q

SAB

A

spontaneous abortion

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9
Q

FTT

A

failure to thrive-doesnt put on weight

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10
Q

Two examples of autosomal dominant inheritance

A

Achondroplasia–GOT midget

Marfan’s Disease

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11
Q

Variable Expressivity (define) and give an example.

A

features of a disorder vary between individuals even in the same family. Usually autosomal dominant disorders have variable expressivity. Example: marfan syndrome

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12
Q

Marfan Syndrome

A

Tall lanky, disorder of connective tissue. Mortality: dilation of the aorta resulting in rupture.

Exhibits variable expressivity: people in same family may have to different degrees

also an example of dysplasia (defect in fibrilin)

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13
Q

Incomplete Penetrance (definition and example)

A

Not all individuals with a mutation have phenotypic effects. Ex: BRCA gene mutation

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14
Q

Explain the difference between variable penetrance, variable expressivity, and having both.

A

EX: BRCA gene. Only some people w/ gene get disorder (variable penetrance). And people who have the gene have different types of cancer (variable expressivity).

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15
Q

De novo mutation

A

New mutations can occur at “hot spots”.
Rate of new mutations increases with advancing paternal age.
Ex:: 80% of achondroplasia cases are de novo.

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16
Q

Examples of recessive inheritance

A

Cystic fibrosis

Sickle Cell

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17
Q

How is cystic fibrosis inherited?

A

recessively.

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18
Q

Is penetrance in autosomal recessive diseases complete or incomplete?

A

usually complete. if you have two copies, you have the disease.

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19
Q

Examples of recessive autosomal inheritance with ethnic correlations

A

Sickle Cell

Tay Sachs

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20
Q

Example of X-linked recessive inheritance and details of disease

A

Hemophilia: bleeding caused by factor 8 deficiency, life expectancy reduction by about 10 yrs.

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21
Q

Characteristics of X-linked diseases

A

Male to male transmission not observed. Males more likely than females to be affected. All daughters of an affected male are carriers. Female carriers may show milder version of trait

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22
Q

Lyonization (X-inactivation)

A

Explains why some female carriers of an x linked disorder might show some characteristics. One x chromosone is turned off in cells. A skewed ratio could lead to a phenotype. An example would be women exhibiting less severe symptoms of duchenne muscular dystrophy.

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23
Q

Duchenne Muscular Dystropy

A

X-linked recessive inheritance. skeletal muscle disease. life expectancy around 27 yrs

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24
Q

When could a female be affected by a recessive X linked disorder?

A
  • Turners syndrome
  • skewed x-inactivation
  • she has an affected father and carrier mother
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25
Q

X-linked dominant inheritance (example)

A

Incontinentia Pigmenti; disorder of skin hair teeth etc. cognitive delays

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26
Q

X-linked dominant inheritance mechanism

A

Females are much more likely than males to be affected. male to male transmission not observed

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27
Q

How many genes on mitochondria?

A

37

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28
Q

MELAS

A

Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes; hearing loss, diabetes, seizures, intellectual disability

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29
Q

Heteroplasmy and Homoplasmy

A

mix of normal and abnormal mtDNA vs. all mt DNA is the same

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30
Q

Threshold effect in mtDNA

A

Threshold for symptoms showing

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31
Q

How does mitochondrial function vary with age?

A

Mt function decreases with age.

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32
Q

Anticipation (definition)

A

Increase in severity of phenotype in successive generations. Related to trinucleotide repeats

33
Q

Example of disease with anticipation

A

Myotonic Dystrophy has a spectrum of severity depending on repeats. affects skeletal and smooth muscle; myotonia–sustained muscle contraction.

Fragile X syndrome
most common inherited cause of intellectual diability. Severity doesnt increase with repeats, but likelihood of having it does

34
Q

Fragile X syndrome characteristics of carriers

A

female carriers have increased risk of early menopause

males are at risk for parkinsons syndrome

35
Q

Mosaic Down syndrome

A

less severely affected. 1-2% of down syndrome.

36
Q

Pallister Killian Syndrome

A

Mosaic tetrasomy 12p.
low muscle tone, characteristic facies, hypopigmentation

Only seen in mosaic form because the non mosaic form is lethal.

37
Q

When should gonadal mosaicism be inferred?

A

When two offspring have an autosomal dominant disorder with no other family history.

38
Q

Why are digynic triploidy and diandric triploidy evidence for imprinting?

A

Because depending on whether you get two copies from mom (digynic) or dad you get a different result.

39
Q

Russell Silver Syndrome

A

small features, triangle face. about 10% of cases occur with uniparental disomy on chromosone 7.

40
Q

Prader-Willi Syndrome

A

Hyperphagia; intellectual disability. “Prader no fader”

41
Q

Angelman Syndrome

A

Severe disability. Caused by lack of genes on the maternal allele

42
Q

Major anomalies vs. Minor anomalies

A

medical surgical intervention needed, cosmetically important.

Minor: no major surgery

43
Q

22q11 deletion syndrome

A

Piece of long arm of 22nd chromosone missing.

74% of kids have a heart defect. palette anomalies, nasal voice.

Looks phenotypically different, have to look at patients carefully.

44
Q

Malformation (definition+ex)

A

Defect from an intrinsically abnormal deveopment process; occurs at 8-10 weeks. ex: heart defect, cleft lip,

45
Q

Deformation (definition +ex)

A

abnormality from mechanical forces; occurs AFTER 8-10 weeks, ex: clubbed foot, overlapping toes. Squished against side of placenta.

46
Q

Disruption (definition+ex)

A

environmental disturbance, think of tunnel being completely blocked wheras in deformation tunnel is only partially blocked.

Ex: oligodactyly–amniotic band compression. cleft palate

47
Q

Dysplasia

A

Abnormal organization of cells into tissues. Ex: polycystic kidney disease. dented chest

48
Q

Syndrome (definition and example)

A

multiple anomalies thought to be pathogenically related

49
Q

Sequence (definition and example)

A

cascade from single known anomaly or MECHANICAL factor.

Ex: Pierre robin sequence.
micrognathia–>glossoptosis–>cleft palette

Potter sequence :
lack of fetal urine–>anhydamnios–> fetal compression–>hypoplasia

50
Q

Field Defect (definition and example)

A

derived from the disturbance of a single developmental field.

Ex: a midline development issue

Ex: OEIS (external bowels)
or holoprosencephaly spectrum

51
Q

Association (definition and example)

A

Non random occurrence of multiple anomalies that cannot be explained by chance. UNKOWN factor.

Ex: VATERAL (Vertebral anomalies, anus, cardiac, TEF, renal, limb

52
Q

Teratogen (definition)

A

exposure in pregnancy with a harmful effect

ex: infection, medications, drugs, heavy metals, procedures

53
Q

Characteristics of teratogens

A

dose response relationship

period of greatest sensitivity

54
Q

Examples of teratogens

A

thalidomide
warfarin (coumadin)
acutane

55
Q

Where are men placed on a pedigree?

A

to the left of females

56
Q

Three principles of mendellian inheritance

A
  1. unit inheritance
  2. segregation
  3. independant assortment
57
Q

What organ systems are most likely to be affected in mitochondrial disorders?

A

Systems w. large ATP requirements. CNS, skeletal muscle, eye muscle, heart muscle (muscles +brain)

58
Q

Heterodisomy vs. isodisomy

A

in heterodisomy, the parent provides one copy of each homologous chromosone. In isodisomy, the parent passes on two IDENTICAL copies of hte same chromosone

59
Q

dysmorphic features

A

variants of physical features that are present in less than 2-3% of population

60
Q

What percent chance is there that a person has a syndrome if they have….
1 anomaly?
2 anomaly?
3 anomaly?

A

1 anomaly: 3% chance
2 anomalies: 10% chance
3 anomalies: 20% chance

61
Q

More examples of teratogens

A

ace inhibitors, androgens, cocaine, vitamin A, some antibiotics

62
Q

Hardy Weinberg and what p and q stand for

A

p^2+2pq+q^2=1

q^2 is incidence of homozygotes=incidence of AR disease

2pq=heterozygotes=incidence of carriers

63
Q

How would you calculate if “at least 1” child will have a disease?

A

At least 1= 1-none

64
Q

Multifactorial genetics (definition)

A

combined contribution of genes and environmental factors in the causation of a particular disease or trait

65
Q

What are the two types of multifactorial traits?

A

quantitative and threshold

66
Q

What is liability in multifactorial inheritance?

A

liability is the total combined genetic and environmental factors that influence the development of a multifactorial disorder or trait

67
Q

can liability be measured?

A

no

68
Q

Examples of liability differences between males and females

A

cleft lip and palate: M>F

congenital hip dysplasia F>M

Pyloric stenosis: M>F

69
Q

Recurrence risk rules

A

Recurrence risk is greater if….

  1. greater severity
  2. more than one family member is affected
  3. more closely related family members
  4. if proband is of less commonly affected sex
  5. recurrence risk of 1st d relative is equal to square root of population incidence
70
Q

heritability (definition)

A

How much of a phenotypic variance is caused by genes vs environment?

71
Q

Genetic risk factors of AD

A

Apolipoprotein E (APOE) : if you have a copy of the e4 allele, your risk increases 2-5x; if you have 2 copies your risk increases 5-10x

72
Q

What is recurrence risk rate for birth defects?

A

4%

73
Q

polygenic trait

A

results from the combined influence of multiple genes

74
Q

Signs of multifactorial inheritance

A

familial concentration
absence of clear biochemical defects from 1 gene
variation in severity and expression
gender differences

75
Q

What percent of breast cancer is due to an inherited change? (BRCA, p53, etc)

A

about 5-10%

76
Q

If you see a pedigree with only affected women, what is the mode of inheritance?

A

X linked dominant

77
Q

What percent of children are diagnosed with a birth defect at birth? after 1 year?

A

3%, 4%

78
Q

Concurrence of minor and major anomalies

A

If a child has 3 or more minor anomalies, 20-90% more likely to have a major malformation

Genetics (2 decks)

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