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clin med > genetics > Flashcards

genetics Flashcards

1
Q

types of prenatal genetic analysis

A

Karyotype, FISH, microarray, genome sequencing

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2
Q

how many generations should be tested in the genetic work-up?

A

2-3 generations

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3
Q

what should be used in the standard pedigree info?

A 
initials/names of family
ages or DOB
ages and cause of death
details of a disorder
min of 2-5 generations
ethnic background including religious group
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4
Q

who are at-risk family members?

A 
consanguinity
ashkenazi jews
african, mediterranean
BRCA
caucasians
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5
Q

what is termed as the physical location of a gene?

A

locus

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6
Q

what is the version of a gene? letter used to represent a gene

A

allele

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7
Q

what is considered a “normal” allele?

A

wild-type

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8
Q

what is considered an abnormal version of the gene associated with a trait/disorder?

A

mutant

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9
Q

structures which house the gene

A

chromosome

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10
Q

how many chromosomes do we have?

A

46 (23 pairs)

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11
Q

what is the “central dogma”

A

process of replication, transcription and translation

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12
Q

what is the message(nucleotides) encoded in RNA called? 3 letter words

A

codon

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13
Q

what are the first 22 pairs of chromosomes called?

A

autosomes

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14
Q

What are a combination of alleles at adjacent locations on a chromosome that are inherited together. Or a set of single-nucleotide polymorphisms

A

haplotype

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15
Q

Production of RNA using DNA code as template

A

transcription

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16
Q

Production of a protein using RNA code as template

A

Translation

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17
Q

Actively forming the string of proteins in to a 3D form that can be used by the body

A

folding

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18
Q

sites at which a single letter in the DNA code has been swapped for a single alternate letter

A

single nucleotide polymorphisms (SNPs)

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19
Q

Produces a new cell with the same number of chromosomes as the original

A

mitosis

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20
Q

Occurs in Germ cells, Two phases

A

meiosis

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21
Q

Occurs with autosomes (somatic)

A

mitosis

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22
Q

most compact phase of mitosis?

A

metaphase

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23
Q

two nuclear membranes form in which stage of mitosis?

A

telophase

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24
Q

The centromere splits, start to draw to opposite ends during which stage of mitosis?

A

anaphase

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25
Q

This is when different mutations occur on the same gene

A

allelic heterogeneity

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26
Q

This occurs when different genes cause the same disease (e.g. hearing loss)

A

Locus/non-allelic heterogeneity

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27
Q

This occurs when different phenotypes occur with mutations on the same gene (e.g. RET gene lic heterogeneity associated with Hirschprungs and Multiple Endocrine Neoplasia)

A

Phenotypic heterogenity

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28
Q

what is penetrance?

A

when you inherit the gene, but are “normal” - incomplete penetrance (Ex BRCA)

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29
Q

what is expressivity?

A

seen in all that have the gene, but expressed differently (variable expressivity, such as Marfan’s)

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30
Q

Increased severity in subsequent generations
CNS disorders
Trinucleotide repeat expansion
HD, Myotonic dystrophy

A

anticipation

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31
Q

what is x-linked?

A

no male to male, all daughters of males are carriers

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32
Q

what is co-dominance?

A

both alleles of the gene pair contribute to the phenotype (blood groups)

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33
Q

what are examples of non-mendelian inheritance?

A

genomic imprinting
mosaicism
mitochondrial DNA mutations

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34
Q

autosomal dominant disorders

A 
huntington disease
myotonic dystrophy
Neurofibromatosis,Tuberous Sclerosis
Urinary Polycystic Kidney Disease, Familial Adenomatous Polyposis, Marfan’s syndrome
Ehlers-Danlos syndrome
35
Q

Autosomal Recessive Disorders

A 
Cystic Fibrosis
Sickle Cell Anemia
Tay-Sachs Disease
Phenylketonuria (PKU)
Galactosemia
Homocystinuria
Lysosomal storage disease
Fredereich ataxia
Spinal muscular atrophy
36
Q

X-Linked Disorders

A

Male-hemizygous (Y not homologous to X)
Heterozygous female can manifest some symptoms (less than male)
Example: G6PD deficiency

37
Q

example of y-linked disorder

A

sertoli-only cell syndrome (complete absence of germ cells in testis)

38
Q

what are mitochondrial disorders?

A

maternal inheritance, leber hereditary optic neuropathy

39
Q

what is mosaicism?

A

Mitotic errors develop early and result in two or more populations of cells with different chromosomal information in the same person.
Common in X, Y

Occurs post-zygotically

40
Q

This chromosome occurs when two broken ends of the same chromosome fuse

A

ring

41
Q

This is when a chromosome breaks and the fragment re-attaches to the original chromosome in a reverse orientation

A

inversion

42
Q

This is when a chromosome lacks certain genes or there is an absence of a segment of DNA.

A

deletion

43
Q

I am a point mutation that exhanges a nucelotide for another one= changes in amino acids. may affect protein function

A

missence

44
Q

sickle cell disease is an example of what type of mutation?

A

missence

45
Q

I am a point mutation changing a codon for an amino acid into a STOP codon.Usually non-functional

A

nonsense

46
Q

autosomal dominant disorder characterized by the development of bilateral vestibular schwannomas. average age of onset is 18-24 years

A

NF2 (bilateral acoustic neurofibromatosis, or central NF)

47
Q

autosomal dominant disorder which manifests in the 3rd or 4th decade and leads to complaints of muscle stiffness and is evidenced by the marked delay that occurs before affected muscles can relax after a contraction

A

myotonic dystrophy

48
Q

what is the most life threatening inherited disease worldwide? characterized by numerous fluid-filled cysts that result in massive enlargement of the kidneys

A

polycystic kidney disease

49
Q

difference between Autosomal Recessive Polycystic Kidney disease and autosomal dominant

A

autosomal recessive is a disease of childhood and linked to hetogenous mutations in a single gene.
autosomal dominant mostly seen in adults which leads to uncontrolled/regulated cell growth

50
Q

Gene that provides instructions for making a protein called fibrocystin (sometimes known as polyductin) which is present in adult and fetal kidney cells.

A

PKHD I

51
Q

what is the function of PKHD I that we are concerned with in PKD?

A

cell proliferation

52
Q

autosomal dominant disorder where the person will have hundreds to thousands of adenomatous polyps in the colon and has a nearly 100% risk of developing CA by middle age if colon is not surgically removed

A

Familiar Adenomatous polyposis (FAP)

53
Q

what do FAP patients present with?

A

numerous colorectal ademonas by the second or third decade of life

54
Q

autosomal dominant disorder which causes defects in in collagen and other proteins of various tissues. patients will have skin elasticity, joint hypermobility, tissue fragility, multiple ecchymoses, and subcutaneous pseudotumors

A

Ehlers-Danlos Syndrome

55
Q

autosomal dominant connective-tissue disorder. cardinal features: tall stature, ectopia lentis, mitral valve prolapse, aortic root dilation, and aortic dissection

A

marfan syndrome

56
Q

what percentage of marfan’s patients have an affected parent?

A

3/4

57
Q

is marfan syndrome fully penetrant?

A

yes

58
Q

marfan syndrome results from mutations in which gene?

A

fibrillin I gene which encodes for the glycoprotein fibrillin - a major building block of microfibrils, which constitute the structural components of the suspensory ligament of the lens

59
Q

abnormalities involving microfibrils in marfan’s weaken what?

A

the aortic wall, which leads to progressive aortic dilation and eventual aortic dissection

60
Q

4 major diagnostic findings for marfan syndrome

A

dilation or dissection of the aorta@ level of the sinuses of valsalva

ectopia lentis

dural ectasia

4 or 8 specific skeletal features

61
Q

autosomal dominant. this is the “receptor disease” caused by a mutation of the gene encoding the receptor fo rLDL, which is involved in the transport and metabolism of cholesterol

A

familial hypercholesterolemia - as a consequence of the receptor abnormalities there is a loss of feedback control and the patient will develop elevated cholesterol levels. 1 in 500 individuals

  • heterozygotes with one mutant gene: 2-3 fold elevation in plasma cholesterol
  • Homozygotes: most severely affected, 5-6 fold increase in plasma cholesterol levels
62
Q

co-dominant disorder where there is a deficiency of the protease inhibitor alpha I-antitypsin which results in a predisposition to pulmonary emphysema and hepatic cirrhosis. accounts for approximately 2% of COPD cases in america

A

alpha I antitrypsin Deficiency

63
Q

autosomal recessive disorder caused by a defect in the PAH gene which codes for pheylalanine hydroxylase, an enzyme that converts phenylalanine to tyrosine in the liver. part of newborn screen, with strict adherence to diet can avoid most of the symptoms.

A

PKU

64
Q

clinical signs/symptoms of PKU

A

fair skin, blonde hair, blue eyes.
mental retardation, hyperactivity, seizures and eczema characterize untreated patients. hallmark sign “mousy” odor of hair, skin and specifically urine

65
Q

treatment of PKU

A

restrict dietary pheylalanine and supplement tyrosine

66
Q

autosomal recessive disorder caused by almost total I-phosphate uridyl transferase deficiency. accumulation of galactose I-phosphate which results in injury to parenchymal cells of the kidney, liver and brain

A

galactosemia

Tx is a galactose free diet

67
Q

autosomal recessive disorder involving a gene that is involved in copper transport. leads to increased copper storage and ultimately liver disease

A

wilson’s disease

68
Q

when does wilson’s disease first appear?what is the initial feature?

A

between ages of 6 and 40. liver disease (jaundice, fatigue, loss of appetite and abdominal swelling)

69
Q

autosomal recessive disease causing hexosaminidase A deficiency. Ashkenazi jews. relentless deterioration of mental and physical abilities which commences at six months of age and usually results in death by the age of four

A

Tay Sachs

*no treatment for these patients

70
Q

most common cause of inherited MR

A

fragile X syndrome

71
Q

clinical features of fragile X

A 
large protruding ears
large testes
elongated face
stereotypic movements (hand flapping)
CGG trinucleotide repeated
72
Q

chromosomal abnormality involing absence of all or part of one X chromosome (X monosomy). most common sex chromosome abnormality of human females. (45, XO karyotype)

A

turner syndrome

73
Q

keys to diagnosis of turner syndrome

A

short stature with normal GH levels

hypogonadism
primary amenorrhea or early ovarian failure

epicanthal folds, webbed neck, short fourth metacarpals

renal and cardiovascular anomalies

74
Q

syndrome characterized by severe hypotonia and feeding difficulties in early infancy followed in later infancy or early childhood by excessive eating and gradual development of morbid obesity

A

prader willi syndrome

75
Q

down’s syndrome, major cause of mental retardation. chromosome count is 47

A

trisomy 21

76
Q

characteristics of trisomy 21

A

Flat facial profile
Oblique palpebral fissures
Epicanthic folds

Predisposed to Leukemia, Congenital Heart disease and early Alzhiemers

77
Q

edwards syndrome, associated with severe intellectual disability, many infants die within their first month

Low birth weight
Small, abnormally shaped head
small jaw and mouth
Clenched fists with overlapping fingers; heart defects
Abnormalities of other organs.
A

trisomy 18

78
Q

patau syndrome. nearly 50% die within the first month, relatively few survive past 3 years of age
Holoprosencephaly
Eye anomalies (microphthalmia, anophthalmia, or coloboma)
Cleft lip and palate
Polydactyly
Cardiac defects
Low birth weight

A

trisomy 13

79
Q

characterized by an extra copy of the Y chromosome in each of a man’s cells. may be taller than average

A

XYY - most males with this have normal sexual development and are able to father children

Associated with an increased risk of learning disabilities and delayed development of speech and language skills.
Delayed development of motor skills (such as sitting and walking), hypotonia, motor tics, and behavioral and emotional difficulties are also possible.
These characteristics vary widely among affected boys and men

80
Q

trisomy X, characterized by the presence of an additional X chromosome in each of a female’s cells. may be taller than average

A

XXX

81
Q

one of the most frequent forms of genetic disease involving the sex chromosomes as well as one of the most common causes of hypogonadism in males.

A

Klinefelter syndrome - rarely diagnosed before puberty

82
Q

this is a component of the 22QII deletion syndrome

A

DiGeorge syndrome - fairly common (1 in 4,000), often missed because of variable clinical features

83
Q

clinical features of DiGeorge Syndrome

A 
congenital heart defects
abnormalities of the palate
facial dysmorphism
developmental delay
Variable degrees of T-cell immunodeficiency
Hypocalcemia

clin med (12 decks)

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