FINAL: MOLECULAR DETECTION OF INHERITED DISEASE

Question 1

Caused by mutations (changes) in germ cells that are passed down from parent to child

Answer 1

Inherited Diseases

Question 2

Mutations in Somatic Cell:

Answer 2

1. Cancer
2. Congenital malformations
   (present at birth)
   - due to factors upsetting the developmental process

Question 3

abnormal chromosome #

Answer 3

GENOME MUTATION

Question 4

more than 2

Answer 4

POLYPLOIDY

Question 5

gain (trisomy) or loss
(monosomy)

Answer 5

ANEUPLOIDY

Question 6

Genome mutations Detection?

Answer 6

karyotyping, ploidy
analysis, flow cytometry, & FISH

Question 7

• 2 or more genetically distinct populations of cells from 1 zygote in an individual
• Results from mutation events affecting somatic/germ cells

Answer 7

Mosaicism

Question 8

• Trisomy 21, 47,XY, + 21
• 1/700 live births
• Flat facial profile, mental retardation, cardiac problems, risk of acute leukemia, eventual neuropathological disorders, abnormal immune system

Answer 8

Down syndrome

Question 9

• Trisomy 18, 47,XY, + 18
• 1/3,000 live births
• Severe, clenched fi st; survival less than 1 year

Answer 9

Edward syndrome

Question 10

• Trisomy 13, 47,XY, + 13
• 1/5,000 live births
• Cleft palate, heart damage, mental retardation, survival
  usually less than 6 mo

Answer 10

Patau syndrome

Question 11

• 47,XXY
• 1/850 live births
• Male hypogonadism, long legs, gynecomastia (male breast enlargement), low testosterone level

Answer 11

Klinefelter syndrome

Question 12

• 47,XYY
• 1/1,000 live births
• Excessive height, acne, 1%–2% behavioral disorders

Answer 12

XYY syndrome

Question 13

• 45,X and variants
• 1/2,000 live births
• Bilateral neck webbing, heart disease, failure to develop
  secondary sex characteristics, hypothyroidism

Answer 13

Turner syndrome

Question 14

• 47,XXX; 48,XXXX
• 1/1,200 newborn
  females
• Mental retardation increases with increasing X

Answer 14

Multi X females

Question 15

• abnormalities in structure
• Translocations, inversions, deletions,
  duplications, marker chromosomes,
  derivative chromosomes

Answer 15

Chromosomal mutations

Question 16

caused by
chemicals, radiation, chromosome
breakage syndromes (Fanconi
anemia, Bloom syndrome, ataxia
telangiectasia)

Answer 16

Chromosome breakage

Question 17

is a genetically heterogeneous recessive disorder characterized by defective DNA repair

Answer 17

Fanconi anemia

Question 18

• rare genetic disorder characterized by growth retardation, sun sensitive skin lesions, and an increased risk of cancer

Answer 18

BLOOM SYNDROME

Question 19

• rare genetic disorder characterized by progressive neurological dysfunction, immune deficiencies and increase risk of cancer (like lymphoma and leukemia)

Answer 19

ataxia
telangiectasia

Question 20

DETECTION OF CHROMOSOMAL ABNORMALITIES

Answer 20

karyotyping, FISH,
microarray technology (CGH)

Question 21

Examples of Chromosomal Mutations
- del(22q)
- 1/4,000 live births
- CATCH 22 (cardiac abnormality/abnormal facies, T-cell deficit, cleft palate, hypercalcemia)

Answer 21

DiGeorge syndrome and
velocardiofacial syndrome

Question 22

• del(5p)
• 1/20,000–1/50,000
  live births
• Growth deficiency, catlike cry in infancy, small head, mental retardation

Answer 22

Cri du chat syndrome

Question 23

• del(11p
• 1/15,000 live births
• Aniridia (absence of iris), hemihypertrophy (one side of the body seems to grow faster than the other), and other congenital anomalies

Answer 23

Contiguous gene syndrome; Wilms’
tumor, aniridia, genitourinary
anomalies, mental retardation
syndrome

Question 24

affect structural proteins, cell surface receptor proteins, growth regulators, and enzymes

Answer 24

Single-gene diseases

Question 25

DOMINANCE RELATIONSHIPS - Heterozygous phenotype (child = Tt) - Homozygous phenotype (1 parent = TT) Example: height

Answer 25

Complete dominance

Question 26

DOMINANCE RELATIONSHIPS - Offspring phenotype is variably intermediate (combine) between the homozygous & heterozygous parentals - Example: gene affecting hair texture

Answer 26

Partial/incomplete dominance

Question 27

DOMINANCE RELATIONSHIPS - Simultaneously demonstrate the phenotype of both parents - Example: ABO blood group

Answer 27

Codominance

Question 28

- A.K.A. transmission patterns/mode of inheritance - The manner in which a genetic trait, disorder, or risk of disorder is passed from one generation to the next - Determined by examination of family histories

Answer 28

PATTERNS OF INHERITANCE IN SINGLE GENE DISEASES

Question 29

diagram of family phenotype/genotype

Answer 29

Pedigree:

Question 30

3 main patterns:

Answer 30

- autosomal dominant - autosomal recessive - sex-linked (X-linked)

Question 31

- Criteria: a. Males and females can be affected. Male-to-male transmission may occur. b. Males and females transmit the trait with equal frequency. c. Successive generations are affected. d. Transmission stops after a generation in which no one inherits the mutation. - Affected individual = has dominant allele - Parent 1 (affected) x Parent 2 (unaffected) = 50%-100% risk/likelihood of expressing the disease phenotype on the child

Answer 31

Autosomal Dominant Transmission

Question 32

- Criteria: a. Males and females can be affected. b. Affected males and females can transmit the gene, unless it causes death before reproductive age c. The trait can skip generations. d. Parents of an affected individual are heterozygous or have the traits - Affected individuals =homozygous recessive genotypes - Carriers heterozygotes/asymptomatic

Answer 32

Autosomal Recessive Transmission

Question 33

- Common - Always expressed in males o inherit the trait from heterozygote/homozygote mother - Females are carriers and can only be expressed if the causative allele is present in 2 copies o inherit the trait from affected father and affected heterozygote mother - Ichthyosis, color blindness, hemophilia

Answer 33

X-linked recessive transmission:

Question 34

- Rare - Always expressed in females o Passed from male to all daughters M but to no sons - Expressed also in males, with more severe effects - Rickets, Rett syndrome, incontinentia pigmenti, congenital hypertrichosis

Answer 34

X-linked dominant transmission

Question 35

X-linked recessive diseases are carried by females but manifested most often in _______.

Answer 35

MALES

Question 36

- Freq. of expression of disease phenotype in individuals with a gene lesion

Answer 36

Penetrance

Question 37

homozygous recessive INCOMPLETE OR COMPLETE PENETRANCE?

Answer 37

COMPLETE PENETRANCE

Question 38

- Range of phenotypes in individuals with the same gene lesion

Answer 38

Variable Expressivity

Question 39

Molecular Basis of Single-Gene Diseases: - Molecular methods, morphological studies, clinical chemistry

Answer 39

Detection

Question 40

Molecular Basis of Single-Gene Diseases: - physiological, morphological and laboratory results

Answer 40

Final Diagnosis

Question 41

- Cause: incompletely digested macromolecules due to loss of enzymatic degradation (acid hydrolases) - Defects in proteins required for normal lysosomal function → physical abnormalities - Molecular testing: genes that code for the enzymes & their subunits

Answer 41

LYSOSOMAL STORAGE DISEASE

Question 42

LYSOSOMAL STORAGE DISEASE SCREENING?

Answer 42

GENE PRODUCT TESTING

Question 43

LYSOSOMAL STORAGE DISEASE DETECTION OF MUTATION?

Answer 43

DIRECT SEQUENCING

Question 44

Substrate Accumulated: Sphingolipids DISEASE?

Answer 44

Tay–Sachs disease

Question 45

DISEASE: Von Gierke, McArdle, and Pompe disease SUBSTRATE ACCUMULATED?

Answer 45

Glycogen

Question 46

DISEASE: Hurler, Sheie (MPS I), Hunter (MPS II), Sanfi lippo (MPS III), Morquio (MPS IV), Maroteaux– Lamy (MPS VI), Sly (MPS VII) SUBSTRATE ACCUMULATED?

Answer 46

Mucopolysaccharides

Question 47

DISEASE: Pseudo-Hurler polydystrophy SUBSTRATE ACCUMULATED?

Answer 47

Mucolipids

Question 48

DISEASE: Niemann–Pick disease SUBSTRATE ACCUMULATED?

Answer 48

Sulfatides

Question 49

Substrate Accumulated: Glucocerebrosides DISEASE?

Answer 49

Gaucher disease

Question 50

Cause: Single point mutation in the coagulation factor V gene F5 (1q23) at exon 10 (GA at nucleotide 1691,R506Q) - Genotype: heterozygous form (4%- 8% of the general population) & homozygous (0.06%-0.25%) - Molecular methods: PCR-RFLP, SSP-PCR - Other methods: Invader technology, clot- based methods, family history

Answer 50

FACTOR V LEIDEN

Question 51

FACTOR V LEIDEN inherited blood clotting disorder

Answer 51

Thrombophilia

Question 52

Treatment for blood clot/deep venous thrombosis?

Answer 52

anticoagulants

Question 53

- Precursor to thrombin in the coagulation cascade - Autosomal-dominant increased risk of thrombosis: mutation in the 3' untranslated region of the gene that codes for prothrombin or coagulation factor II, F2 (11p11 -q12)x - Laboratory tests: F2 & F5 mutations - Molecular methods: multiplex PCR - RFLP - Phenotypic methods: thrombin time, prothrombin time, platelet count, CBC Other: sequencing of factors XI & XIII

Answer 53

PROTHROMBIN

Question 54

measure changes in light transmittance during clot formation generating a curve

Answer 54

Automated systems

Question 55

METHYLENETETRAHYDROFOLATE REDUCTASE - autosomal recessive disorder caused by deficiency of the 5,10- methylenetetrahydrofolate reductase (MTHFR) gene product o Increased homocysteine levels → predisposition to venous & arterial thrombosis

Answer 55

Hyperhomocysteinemia

Question 56

- Autosomal recessive condition, over absorption of iron from food → pancreas, liver, & skin damage; heart disease; diabetes - Diagnosis: measurement of blood iron levels, transferrin saturation, liver biopsy - Molecular cause: dysfunction of the hemochromatosis type I HFE or HLA- H gene product (C282Y, H63D, S65C) - Indications for mutation testing: clinical symptoms & increased serum ferritin & transferrin-iron saturation - C282Y mutation detection: PCR-RFLP

Answer 56

HEMOCHROMATOSIS

Question 57

- Life-threatening autosomal recessive disorder that causes severe lung damage & nutritional deficiencies - Affects cells that produces mucus, sweat, saliva, & digestive juices → secretions become thick & sticky - Cause: loss of function of the CFTR gene (3-bp deletion F508del & 1,900 other mutations such as G542X, G551D, N1301K, R117H, W1282X, 1717- 1G>A) - Molecular tests for mutation detection: RFLP, PCR-RFLP, HA, temporal-gradient gel electrophoresis, SSCP, SSP-PCR, cleavase, bead array technology, & direct sequencing

Answer 57

CYSTIC FIBROSIS

Question 58

- Group of mono-oxygenase enzymes localized to the ER - Present in high concentrations in the liver & small intestine → enzymes metabolize & detoxify compounds (drugs) - Polymorphisms affect the metabolism of hormones, caffeine, chemotherapeutic drugs, antidepressants, & oral contraceptives: o Tests are used to predict the response to drugs - Detection of polymorphisms: allele-specific PCR - Screening tests: microarray, bead array, sequencing

Answer 58

CYTOCHROME P-450

Question 59

CONDITIONS THAT DO NOT FOLLOW MENDELIAN RULES OF INHERITANCE:

Answer 59

a. Mitochondrial gene mutations b. Genomic imprinting c. Gonadal mosaicism d. Nucleotide-repeat expansion disorders e. Multifactorial inheritance

Question 60

- Maternally inherited - mtDNA o Circular, 16,569 bp, with 37 genes, 1000-nt control region - Mutations affect energy production → muscles & nervous system - Molecular methods: o Large deletions: Southern blot o Point mutations: PCR-RFLP

Answer 60

MITOCHONDRIAL (mt) GENE MUTATIONS

Question 61

mutated mt & normal mt in the same cell

Answer 61

Heteroplasmy

Question 62

Genes that control mitochondrial functions are found in

Answer 62

nuclear genome

Question 63

- Only 1 copy of a gene in an individual (either from mother or father) is expressed, while the other copy is suppressed o Example: mules (male donkey x female horse) & hinnies (male horse x female donkey) - Cause: transcriptionally silencing through histone/DNA modification - Genetic disorders: 1 or other allele of a gene is lost (uniparental disomy)

Answer 63

GENOMIC IMPRINTING

Question 64

- Generation of new mutations in germline cells → giving rise to eggs/sperm carrying the mutation which then becomes a heritable phenotype - Expected when phenotypically normal parents have more than 1 affected child - Example: osteogenesis imperfecta

Answer 64

GONADAL MOSAICISM

Question 65

- Nucleotide repeats, such as STRS (1-10 bp repeating units) can expand in length during DNA replication & meiosis

Answer 65

NUCLEOTIDE-REPEAT EXPANSION DISORDER

Question 66

- expansions of STR w/3-bp repeating units in the gene sequence o Fragile X syndrome o Huntington disease o Idiopathic congenital central hypoventilation syndrome (CCHS)

Answer 66

Triplet-repeat mutations

Question 67

- CGG expansion (up to >2,000 repeats) in the noncoding region 5' to the FMR-1 gene - Symptoms (increase in severity with each generation): learning disorders & mental retardation (IQ~20), long face, large ears, macroorchidism - Detection: o Karyotyping o PCR o Southern blot o Capillary electrophoresis

Answer 67

Fragile X Syndrome

Question 68

- CAG expansion (9-37 repeats to 38-86 repeats) in the huntingtin structural gene (4p16.3) - Symptoms: impaired judgment, slurred speech, difficulty in swallowing, chorea, personality changes, depression, mood swings, unsteady gait, intoxicated appearance - Detection: o Standard PCR methods o Capillary electrophoresis

Answer 68

Huntington Disease

Question 69

- Gene mutations in PHOX2b gene in chromosome 4: insertion of multiple alanine residues - Inadequate breathing while asleep, hypoventilation while awake - Occurs in association with an intestinal disorder (Hirschsprung disease) & symptoms of ANS dysregulation/dysfunction - Detection: ❖PCR w/32P-labeled primer & polyacrylamide gel electrophoresis ❖Standard PCR & agarose gel electrophoresis

Answer 69

Idiophatic Congenital Central Hypoventilation Syndrome (CCHS)

Question 70

- Disorders (& normal conditions) controlled by multiple genetic & environmental factors (nutritional/chemical exposures) - Phenotypes: conditioned by the no. of controlling genes inherited - Detection: o HR-array methods o NGS - Interpretation: o Databases (ClinVar & dbSNP) - Prognostic & diagnostic value of gene mutation analysis: o Annotation of demographics (ethnicity/gender, lifestyles)

Answer 70

MULTIFACTORIAL INHERITANCE