AAB MOLECULAR DIAGNOSTICS REVIEW
PACK 2026 PREMIUM ANSWER
COLLECTION
◉ Example of X-linked dominant inheritance.
Answer: duchenne/becker muscular dystrophy, fragile-x syndrome
◉ Imprinting Disorder.
Answer: -differential marking of specific paternal and maternal
alleles resulting in differential expressions
-alteration in normal imprinting patterns cause disease
◉ Primary mechanism in imprinting disorder.
Answer: DNA methylation
◉ Examples of Imprinting Disorder.
Answer: Prader-Willi/Angelman syndrome, Uniparental disomy
◉ Multifactorial/complex diseases.
Answer: -multiple genes involved
-tend to cluster in families
,◉ Examples of multifactorial/complex diseases.
Answer: thrombophilia, inherited breast cancer, inherited colon
cancer, familial adenomatous polypoposis (FAP), lynch
syndrome/hereditary nonpolyposis cancer (HNPCC)
◉ Peripheral blood.
Answer: -EDTA
-ACD
-Heparin can be used in some circumstances
-clotted/hemolyzed blood very rarely acceptable
◉ Crude lysis (used for DNA extraction).
Answer: detergent + proteinase K
◉ Chelating resin (used for DNA extraction).
Answer: boil & isolate
◉ Spectrometry.
Answer: -measures absorbance of light by nucleic acid
-measure sample optical density (OD) at 260 nm & 280 nm
,◉ 260 nm.
Answer: maximum nucleic acid absorption
◉ 280 nm.
Answer: maximum protein absorption
◉ OD260 = 1.0 corresponds to:.
Answer: approximately 50 ug/ml double stranded DNA
approximately 40 ug/ml single stranded DNA or RNA
◉ OD260/OD280 ratio estimates nucleic acid quality results:.
Answer: 1.8-2.0= pure
greater than 2- RNA contamination
less than 1.6- protein contamination
◉ Stokes Law (Electrophoresis).
Answer: -when electrophoretic driving force = frictional force,
analyte runs through gel matrix at constant velocity
-electrophoretic driving force = charge on molecule and electric field
strength
◉ 2 types of gels.
, Answer: agarose
polyacrylamide
◉ Agarose gels.
Answer: -porous polysaccharide matrix derived from seaweed
-suitable for fragments 200-20 kb bp range depending on gel
concentration
0.7%-4%
◉ Polyacrylamide.
Answer: acrylamide monomer & bis-acrylamide crosslinker
pores smaller
suitable for fragments smaller than 1000 bp
◉ Stringency (nucleic acid hybridization).
Answer: -controls the degree of base pair mismatching that will be
tolerated in a duplex structure
-2 types (Low & High)
◉ Low Stringency.
Answer: high salt, low temperature, and no formamide which favor
shielding of hydrophobic bases from the aqueous environment even
without perfect alignment
PACK 2026 PREMIUM ANSWER
COLLECTION
◉ Example of X-linked dominant inheritance.
Answer: duchenne/becker muscular dystrophy, fragile-x syndrome
◉ Imprinting Disorder.
Answer: -differential marking of specific paternal and maternal
alleles resulting in differential expressions
-alteration in normal imprinting patterns cause disease
◉ Primary mechanism in imprinting disorder.
Answer: DNA methylation
◉ Examples of Imprinting Disorder.
Answer: Prader-Willi/Angelman syndrome, Uniparental disomy
◉ Multifactorial/complex diseases.
Answer: -multiple genes involved
-tend to cluster in families
,◉ Examples of multifactorial/complex diseases.
Answer: thrombophilia, inherited breast cancer, inherited colon
cancer, familial adenomatous polypoposis (FAP), lynch
syndrome/hereditary nonpolyposis cancer (HNPCC)
◉ Peripheral blood.
Answer: -EDTA
-ACD
-Heparin can be used in some circumstances
-clotted/hemolyzed blood very rarely acceptable
◉ Crude lysis (used for DNA extraction).
Answer: detergent + proteinase K
◉ Chelating resin (used for DNA extraction).
Answer: boil & isolate
◉ Spectrometry.
Answer: -measures absorbance of light by nucleic acid
-measure sample optical density (OD) at 260 nm & 280 nm
,◉ 260 nm.
Answer: maximum nucleic acid absorption
◉ 280 nm.
Answer: maximum protein absorption
◉ OD260 = 1.0 corresponds to:.
Answer: approximately 50 ug/ml double stranded DNA
approximately 40 ug/ml single stranded DNA or RNA
◉ OD260/OD280 ratio estimates nucleic acid quality results:.
Answer: 1.8-2.0= pure
greater than 2- RNA contamination
less than 1.6- protein contamination
◉ Stokes Law (Electrophoresis).
Answer: -when electrophoretic driving force = frictional force,
analyte runs through gel matrix at constant velocity
-electrophoretic driving force = charge on molecule and electric field
strength
◉ 2 types of gels.
, Answer: agarose
polyacrylamide
◉ Agarose gels.
Answer: -porous polysaccharide matrix derived from seaweed
-suitable for fragments 200-20 kb bp range depending on gel
concentration
0.7%-4%
◉ Polyacrylamide.
Answer: acrylamide monomer & bis-acrylamide crosslinker
pores smaller
suitable for fragments smaller than 1000 bp
◉ Stringency (nucleic acid hybridization).
Answer: -controls the degree of base pair mismatching that will be
tolerated in a duplex structure
-2 types (Low & High)
◉ Low Stringency.
Answer: high salt, low temperature, and no formamide which favor
shielding of hydrophobic bases from the aqueous environment even
without perfect alignment
