MOLECULAR DIAGNOSTICS - WEEK 1
INTRODUCTION TO MOLECULAR
DIAGNOSTICS EXAM QUESTIONS
WITH COMPLETE ANSWERS
Technical Considerations for Molecular Testing - ANSWER-1. A genetic *target* is
required for a specific disorder
2. Requires an appropriate *source* of nucleic acids
3. Nature of mutation must be known
4. Sensitivity of the detection method should be understood
Molecular-based Analyses - Chromosomal Disorders - ANSWER-Detects the loss,
gain or abnormal arrangement of genetic material. May result in birth defects,
hematopoietic malignancies. Are classified as *monogenic* i.e. resulting from
mutation in a single gene or *polygenic* i.e. resulting from interplay of multiple
genetic factors.
Monogenic Disorder - ANSWER-Chromosomal disorder resulting from a mutation in
a single gene. Conforms to traditional Mendelian inheritance, with a frequency of
10/1000 live births
Polygenic Disorder - ANSWER-Chromosomal disorder resulting from the interaction
of mutations in multiple genes. Unlike monogenic disorders, they do not conform to
Mendelian inheritance patterns. Examples: hypertension, Alzheimer's disease,
Diabetes mellitus, Cancer, congenital malformations
Mutation - ANSWER-*Permanent* alteration of a DNA sequence, usually found in
less than 1% or 2% of a given population
Polymorphism - ANSWER-Difference in DNA sequence found in 1% to 2% or *more*
of a given population
Mutation Structure - ANSWER-Analyzed by *endonuclease digestion* which can
determine variation in fragment lengths.
Hypervariable Regions of DNA - ANSWER-*Minisatellites*: also called Variable
Number Tandem Repeats which are 10-100 bp in length
*Microsatellites*: di-,tri- and tetra-nucleotide repetitive sequences
Tri-nucleotide Repeat Genetics - ANSWER-Three base-pair tandem sequence
repeats in DNA where an expansion of the repeats beyond normal length results in
disease from creation of abnormal gene function/product.
Examples: fragile X, myotonic dystrophy, Huntington disease
Clinical Significance of Mutations - ANSWER-May be used as *diagnostic markers*
with significance determined by mutation type, location and tissue involvement.
, Mutation Types - ANSWER-Germline
Acquired
Point Mutations (e.g. transition - purine/purine, pyrimidine/pyrimidine & translation -
purine/pyrimidine)
*Direct* Molecular Diagnostic Tests - ANSWER-Detects mutations or foreign DNA
sequences when the mutation or gene of interest is *known*. types of tests include:
oligo probes, DNA sequencing, amplification
*Indirect* Molecular Diagnostic Tests - ANSWER-Detects mutations/foreign DNA
when the sequence is *unknown*. Performed by linkage analysis where markers are
tracked through their progress in families with genetic disease. Gene is mapped but
not sequenced.
Disorders Diagnosed via Molecular Technologies - ANSWER-Endocrine
Cardiovascular
Human Neoplastic Disease
Oncogenes
Anti-oncogenes
DNA Damage Repair - ANSWER-Essential function which can result in
mutations/disease if lost. Repair mechanisms include: enzymatic reversal repair,
nucleotide excision repair, post-replication repair
Familial Cancer - ANSWER-Mutations found in DNA of affected parents; passed to
subsequent generations through *germline* transmission. Mutated gene is linked to
susceptibility and *not* detected in normal controls.
E.g. retinoblastoma, breast carcinoma, hereditary colon cancer, ovarian carcinoma,
familia melanoma
Cellular Elements Involved in Growth - ANSWER-Nucleus
Ribosomes
Endoplasmic Reticulum
Golgi Body
Vacuoles
Centrioles
Nucleus - ANSWER-Serves as the storage site of genetic information, place of
ribosome synthesis. Subcomponents include chromatin/chromosomes, nucleolus,
nucleoplasm
Nucleic Acid - ANSWER-Macromolecule made of *nucleotides* bound together by
phosphate and hydroxl groups on their sugars. *Order* of nucleotide bases is the
coding information of the molecule.
Nucleoside - ANSWER-Unite of nucleic acid comprised of a ribose sugar and a
nitrogen-containing base.
INTRODUCTION TO MOLECULAR
DIAGNOSTICS EXAM QUESTIONS
WITH COMPLETE ANSWERS
Technical Considerations for Molecular Testing - ANSWER-1. A genetic *target* is
required for a specific disorder
2. Requires an appropriate *source* of nucleic acids
3. Nature of mutation must be known
4. Sensitivity of the detection method should be understood
Molecular-based Analyses - Chromosomal Disorders - ANSWER-Detects the loss,
gain or abnormal arrangement of genetic material. May result in birth defects,
hematopoietic malignancies. Are classified as *monogenic* i.e. resulting from
mutation in a single gene or *polygenic* i.e. resulting from interplay of multiple
genetic factors.
Monogenic Disorder - ANSWER-Chromosomal disorder resulting from a mutation in
a single gene. Conforms to traditional Mendelian inheritance, with a frequency of
10/1000 live births
Polygenic Disorder - ANSWER-Chromosomal disorder resulting from the interaction
of mutations in multiple genes. Unlike monogenic disorders, they do not conform to
Mendelian inheritance patterns. Examples: hypertension, Alzheimer's disease,
Diabetes mellitus, Cancer, congenital malformations
Mutation - ANSWER-*Permanent* alteration of a DNA sequence, usually found in
less than 1% or 2% of a given population
Polymorphism - ANSWER-Difference in DNA sequence found in 1% to 2% or *more*
of a given population
Mutation Structure - ANSWER-Analyzed by *endonuclease digestion* which can
determine variation in fragment lengths.
Hypervariable Regions of DNA - ANSWER-*Minisatellites*: also called Variable
Number Tandem Repeats which are 10-100 bp in length
*Microsatellites*: di-,tri- and tetra-nucleotide repetitive sequences
Tri-nucleotide Repeat Genetics - ANSWER-Three base-pair tandem sequence
repeats in DNA where an expansion of the repeats beyond normal length results in
disease from creation of abnormal gene function/product.
Examples: fragile X, myotonic dystrophy, Huntington disease
Clinical Significance of Mutations - ANSWER-May be used as *diagnostic markers*
with significance determined by mutation type, location and tissue involvement.
, Mutation Types - ANSWER-Germline
Acquired
Point Mutations (e.g. transition - purine/purine, pyrimidine/pyrimidine & translation -
purine/pyrimidine)
*Direct* Molecular Diagnostic Tests - ANSWER-Detects mutations or foreign DNA
sequences when the mutation or gene of interest is *known*. types of tests include:
oligo probes, DNA sequencing, amplification
*Indirect* Molecular Diagnostic Tests - ANSWER-Detects mutations/foreign DNA
when the sequence is *unknown*. Performed by linkage analysis where markers are
tracked through their progress in families with genetic disease. Gene is mapped but
not sequenced.
Disorders Diagnosed via Molecular Technologies - ANSWER-Endocrine
Cardiovascular
Human Neoplastic Disease
Oncogenes
Anti-oncogenes
DNA Damage Repair - ANSWER-Essential function which can result in
mutations/disease if lost. Repair mechanisms include: enzymatic reversal repair,
nucleotide excision repair, post-replication repair
Familial Cancer - ANSWER-Mutations found in DNA of affected parents; passed to
subsequent generations through *germline* transmission. Mutated gene is linked to
susceptibility and *not* detected in normal controls.
E.g. retinoblastoma, breast carcinoma, hereditary colon cancer, ovarian carcinoma,
familia melanoma
Cellular Elements Involved in Growth - ANSWER-Nucleus
Ribosomes
Endoplasmic Reticulum
Golgi Body
Vacuoles
Centrioles
Nucleus - ANSWER-Serves as the storage site of genetic information, place of
ribosome synthesis. Subcomponents include chromatin/chromosomes, nucleolus,
nucleoplasm
Nucleic Acid - ANSWER-Macromolecule made of *nucleotides* bound together by
phosphate and hydroxl groups on their sugars. *Order* of nucleotide bases is the
coding information of the molecule.
Nucleoside - ANSWER-Unite of nucleic acid comprised of a ribose sugar and a
nitrogen-containing base.
