Lab tests

Question 1

Nernst potential

Answer 1

membrane potential at which there is 0 net driving force; value of membrane potential that balances an ion’s concentration gradient exactly

driving force = (membrane potential) - (Nernst potential)

when Nernst is far from membrane potential, there is a large driving force

Question 2

Southern blot

Answer 2

DNA

gel electrophoresis

Question 3

Northern blot

Answer 3

RNA (gene expression)

gel electrophoresis

Question 4

Western blot

Answer 4

presence of proteins (antibodies radiolabeled)

gel electrophoresis; more specific than ELISA, but only qualitative

Question 5

ELISA (enzyme-linked immunosorbent assay)

Answer 5

proteins (presence and concentration)

less specific than Western blot, but quantitative

Question 6

mass spectrometry

Answer 6

used to identify protein/post-translational modifications

Question 7

PCR (polymerase chain reaction), qPCR/RT-PCR

Answer 7

PCR: amplification of chromosome segments (small DNA seq)

qPCR/RT-PCR: quantifying SNPs for mRNA or DNA

Question 8

Traditional Sanger Sequencing

Answer 8

uses PCR + ddNTPs to sequence genome

can be used for single gene/syndrome sequencing (small differential)

Question 9

next-generation sequencing

Answer 9

DNA + beads, looks at pH difference

can be used for:
- single gene/syndrome sequencing (small differential)
- phenotype specific panel testing

Question 10

whole exome/genome sequencing (WES/WGS)

Answer 10

best used if there is no high clinical suspicion of a recognized genetic disorder

can also be used as a last resort for sequencing point/small mutations

Question 11

karyotyping

Answer 11

to check for aneuploidies

Question 12

FISH (fluoresence in situ hybridization)

Answer 12

specific DNA sequence bound with fluorescent probes

to be used when there is a chromosomal abnormality and the specific DNA seq of mutation is known

Question 13

chromosomal microarray

Answer 13

microchip-based testing

method for detecting copy number changes (gains or losses) across the entire genome; used when there is no high clinical suspicion of disorder

Question 14

site specific testing

Answer 14

tests for known mutation in the family

Question 15

CRISPR/Cas 9

Answer 15

used to add/delete genes in DNA sequences

Question 16

RNAi (RNA interference)

Answer 16

DICER cleaves, RISC destroys identical RNA strands (hairpin loop)

Question 17

Cre-Lox system

Answer 17

used to induce recombination between specific DNA sites (e.g., to study the effect of gene insertions or deletions)

Question 18

prenatal diagnostic test: preimplantation

Answer 18

preimplantation genetic diagnosis (PGD): blastocyst bopsy (IVF technique)

tests if a specific genetic change is present in an embryo

Question 19

prenatal screening & diagnostic tests: first trimester

Answer 19

screening:
- first trimester screen: ultrasound + maternal serum, screens for trisomy 21 & 18
- non-invasive prenatal screening (NIPT) AKA cell-free DNA (cfDNA) testing: maternal serum, screening for trisomies 21, 18, 13

diagnostic:
- chorionic villus sampling (CVS): boipsy of tissue from chorion

Question 20

prenatal screening & diagnostic tests: second trimester

Answer 20

screening:
- quad or triple screen AKA maternal serum alpha-fetoprotein (MSAFP): maternal serum, screens for trisomies 21 & 18, neural tube defects (NTD)
- anatomy ultrasound: anatomical alterations and NTDs

diagnostic:
- amniocentesis: amniotic fluid (needle), cells of fetal origin
- percutaneous umbilical blood sampling AKA cordocentesis: umbilical cord sample of fetal blood