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Medical Genetics > Exam 2 - Genetic testing and Gene therapy > Flashcards

Exam 2 - Genetic testing and Gene therapy Flashcards

Genetic testing and Gene therapy

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1
Q

Goal of screening

A

Early identification of a disorder so that intervention can prevent or reverse the disease process

Assist in reproductive decisions

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2
Q

Determines the genotypes in individuals that:

A

1) Already have a disease or predisposed to a disease
e. g. newborn screening
2) Are presymptomatic for a disease
e. g. Huntington disease, breast cancer, colon cancer

3) May have a disease genes that could be passed down to descendants
e. g. Fragile X gene in carrier females

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3
Q

Parameters for genetic screening tests:

A

Validity
Specificity
Sensitivity

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4
Q

Validity

A

Refers to the ability of a test to separate individuals who have the disease from those who do not.

Validity involves 2 components: sensitivity and specificity

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5
Q

Sensitivity

A

the ability to correctly identify those with the disease . It is measured as the proportion of affected individuals who test positive (i.e. true positives)

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6
Q

Specificity

A

ability to correctly identify those without the disease. It is measured as the proportion of unaffected individuals in whom the test is negative (i.e. true negatives)

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7
Q

_____ and _____ are determined by comparing the screening results with those of a _____ diagnostic test

A

Sensitivity
specificity
definitive

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8
Q

Test result vs true status

A

(true status)
+ -
(test) + A B

        -    C     D
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9
Q

Sensitivity (calc)

A

a/a+c

Probability that test is positive when person actually has the disease

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10
Q

Specificity (calc)

A

d/b+d

Probability that test is negative when person truly does NOT has the disease

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11
Q

False Positive

A

b/b+d

Test reports positive for person who does NOT have the disease

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12
Q

False Negative

A

c/a+c

Test reports negative for person who actually has the disease

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13
Q

High ____ value results in high ____

A

“a”

sensitivity

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14
Q

High ____ value results in high ____

A

“d”

specificity

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15
Q

PPV

A

Positive Predictive value

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16
Q

Positive Predictive value

A
  • Proportion of positive test results that are truly positive
  • answers the question: if my test is positive, what is the chance that I am truly positive for the condition?
  • a/a+b
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17
Q

NPV

A

Negative Predictive value

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18
Q

Negative Predictive value

A

Proportion of negative test results that are truly negative

Answers the question: if my test is negative, what is the chance that I am truly unaffected??

d/c+d

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19
Q

____ of a test varies based on _____ of the condition in a given pop

A

PPV

prevalence

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20
Q

The ____ the condition in a given pop, lower the ____

A

rarer

PPV

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21
Q

More detailed PPV calculation

A

Sensitivity x prevalence
(divided by)
(sensitivity x prevalence) + (1-specificy) (1-prevalence)

22
Q

In trying to cast a wider net to catch more patients, the trade off is having __________

A

increased false-positive rate

23
Q

Screening tests are never 100% ____ and 100% ____.

A

sensitive

specific

24
Q

non- invasive pre-natal screening methods:

A 
Ultrasound 
Nuchal Translucency Index
Maternal Serum screening 
Triple screen; quad screen 
Fetal cells 
Cell free fetal DNA
25
Q

Invasive pre-natal diagnostic methods:

A

Amniocentesis
Chorionic Villus Sampling (CVS)
Percutaneous Umbilical Blood Sampling

26
Q

Ultrasound

A

Can be used to determine presence of spina bifida (meningomyelocele) displayed as a fluid filled sac in the spinal column

27
Q

Nuchal Translucency Index

A

Uses ultrasound to measure the translucent space in the tissue at the back of your developing baby’s neck.

28
Q

Nuchal Translucency Index used to determine:

A

baby’s risk for Down syndrome (DS) and other chromosomal abnormalities, as well as major congenital heart problems.

29
Q

Babies with abnormalities tend to accumulate more:

A

fluid at the back of their neck during the first trimester. Result is an enlargement in this region

30
Q

US vs Sonogram

A

US - the machine that allows you to see your baby during your pregnancy

Sonogram - the picture taken of your baby during the ultrasound.

31
Q

______ take _____ images, or 3D sonograms, and adds the element of time to the process.

A

4D Ultrasounds

3D Ultrasound

32
Q

In prenatal screening, confirmation of a _____ result should be followed up with _____

A

positive

diagnostic testing

33
Q

Amniocentesis

A

20-30 mL of amniotic fluid is withdrawn transabdominally with US guidance

34
Q

Amniocentesis usually occurs:

A

15-17 weeks gestation

35
Q

CVS procedure:

A

a catheter is inserted through the cervix and several mg of villus tissue is suctioned with US guidance

36
Q

Fetal treatment is _____

A

rare

37
Q

Fetal treatment used in the following 3 conditions:

A

Congenital Adrenal Hyperplasia
Biotin-responsive Multiple Carboxylase Deficiency
fetal surgery for a neural tube disorder

38
Q

In NBS, _____ screen results need to be followed up with further _______ that is specific for _________

A

Positive
confirmation testing
each condition identified

39
Q

Methods of DNA analysis of biosamples:

A

PCR
ASO (allele specific oligonucleotide) using dot blot
DNA sequencing
Many other methods

40
Q

allele specific oligonucleotide used frequently for:

A

Sickle cell and cystic fibrosis

41
Q

_________ Is the UltimateWay to Characterize a Clone

A

DNA Sequencing

42
Q

DNA that you saturate the filter paper with (ASO method)

A

Probe

43
Q

Antisense strand

A

Sample DNA from patient that complements either prode

44
Q

Based off how the hybridization occurs in ASO:

A

You can tell whether patient is homozygous normal, a carrier, or diseased

45
Q

Newer methods of sequencing associated with Next Generation Sequencing (NGS):

A

Pyrophosphate sequencing

46
Q

DNA sequencing by the _______ developed by _____

A

chain termination method

Sanger

47
Q

Pyrophosphate sequencing relies on the “___________” principle rather than chain termination

A

sequencing by synthesis

48
Q

Pyrophosphate sequencing step 1:

A

ss DNA template is immobilized, and solutions of A, C, G, and T nucleotides are added sequentially to allow for synthesis of complementary strand. Unattached nucleotides are washed off

49
Q

Pyrophosphate sequencing step 2:

A

Light is emitted when the nucleotide attaches to template. The sequence of light signals allows determination of DNA template sequence.

50
Q

ATPs role in Pyrophosphate sequencing

A

ATP acts as fuel for luciferase-mediated conversion of luciferin to oxyluciferin that generates visible light in amounts that are proportional to the amount of ATP.

51
Q

How is light captured in Pyrophosphate sequencing

A

Light produced in the luciferase-catalyzed reaction is detected by a camera/scanner

Medical Genetics (12 decks)

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