Genetics Flashcards Preview

Question 1

1

Codominance
Definition
Example

Answer

Bole alleles contribute to the phenotype of the heterozygote
Blood Group A, B, AB

Question 2

2

Variable Expressivity
Definition
Example

Answer

Phenotype varies among individual with same genotype
Neurofibromatosis type 1

Question 3

3

Incomplete Penetrance
Definition
Example

Answer

Not all individuals with the mutant genotype show the mutant phenotype
BRCA1 gene mutation do not always result in breast or ovarian cancer

Question 4

4

Pleiotropy
Definition
Example

Answer

One gene contributes to multiple phenotypic effects
PKU

Question 5

5

Imprinting
Definition
Physiology
Example

Answer

Differences in gene expression depend on whether the mutation is of maternal or paternal origin
At some loci, only 2 allele is active depending on which parent it came from
Prader Willi and Angelman's Syndrome

Question 6

6

Anticipation
Definition
Example

Answer

Increased severity or earlier onset of disease in succeeding generations
Huntington's Disease

Question 7

7

Loss of Heterozygosity
Definition
Example

Answer

Two Hits needed for disease, born with one mutation
Retinoblastoma and other tumor suppressors

Question 8

8

Dominant Negative
Definition
Example

Answer

Heterozygote produces disease
Nonfunctional TFs binding prevents wild-type from binding

Question 9

9

Linkage Disequilibrium
Definition
Where is it measured

Answer

Tendency for certain alleles at 2 linked loci to occur together more often than expected by chance
Measured in a population, not in a family, and often varies in different populations

Question 10

10

Mosaicism
Definition
Where can it occur
Example

Answer

Cells in the body differ in genetic make up due to post fertilization loss or change of genetic information during mitosis
Can be germ-line which produces disease not carried by either parent's somatic cells
Bone marrow stem cells --> hematologic mosaic. Fused zygote

Question 11

11

Locus Heterogeneity
Definition
Example

Answer

Mutations at different loci can produce the same phenotype
Marfan's, MEN2B, and Homocystinuria can all cause marfanoid habitus. Albinism

Question 12

12

Heteroplasmy
Examples

Answer

Presence of both normal and mutated mtDNA resulting in variable expression in mitochondrial inherited disease
Myclonic Epilepsy

Question 13

13

Uniparental disomy
What is it?
How do you tell when the error happened?

Answer

Offspring receives 2 copies of a chromosome from 1 parent and no copies from the other
Heterodisomy (heterozygous): Meiosis I error
Isodisomy (homozygous): Meiosis II error or post zygotic loss of 1 chromosome and duplication of the other

Question 14

14

Hardy-Weinberg Population Genetics
Equation
Assumptions
In X linked recessive disease

Answer

(p^2) + 2pq + (q^2) = 1 and p+q=1
No mutations, Selection, Migrations and random mating
The frequency of an X linked recessive disease in males is q and in females is (q^2)

Question 15

15

Prader-Willi Syndrome
Chromosome
Which allele is not expressed?
What can cause it?
Presentation

Answer

Inactivation or deletion on chromosome 15
Paternal allele is not expressed
Can also occur as a result of uniparental disomy
Mental retardation, hyperphagia, obesity, hypogonadism, hypotonia

Question 16

16

Angelman's Syndrome
Chromosome
Which allele is not expressed?
What can cause it?
Presentation

Answer

Inactivation or deletion on chromosome 15
Maternal allele is not expressed
Can also occur as a result of uniparental disomy
Mental retardation, Seizures, Ataxia, Inappropriate laughter

Question 17

17

Hypophosphatemic rickets
PathoPhys
Presentation
Genetics

Answer

↑ Phosphate wasting in PT of kidney
Rickets-like presentation
X linked Dominant

Question 18

18

Mitochondrial myopathies
Genetics
PathoPhys
Presentation
Histo

Answer

Mitochondrial Inheritance
Mutations affecting Mito function
Myopathy and CNS disease (seizures)
Muscle biopsy shows ragged red fibers

Question 19

19

Familial Hypercholesterolemia
AKA
PathoPhys
Blood test
Heterozygotes vs Homozygotes
Presentation
Risk of what?

Answer

Hyperlipidemia Type IIA
Absent of defective LDL receptor
Elevated LDL in blood
Heterozygotes have cholesterol of 300
Homozygotes have cholesterol of 700
Severe atherosclerotic disease in early life. Tendon xanthoma (classically in the achilles tendon)
MI may develop before age 20

Question 20

20

Hereditary Hemorrhagic Telangiectasia
AKA
What organ system affected? How?
Genetics
Presentation

Answer

Osler-Weber-Rendu Syndrome
Disorder of blood vessels with arteriovenous malformations
Autosomal dominant
Telangiectasia, Recurrent Epistaxis, Skin discoloration

Question 21

21

Hereditary Spherocytosis
Inheritance
What happens?
Mutation
Presentation
Treatment

Answer

Autosomal dominant
Spheroid erythrocytes
Spectrin or Ankyrin defective
Hemolytic anemia, ↑ mean corpuscular hemoglobin concentration (MCHC)
Splenectomy is curative

Question 22

22

Huntington's Disease
Inheritance
Presentation
Gross
PathoPhys
Age of onset
Genetics with chromosome and pathology

Answer

Autosomal dominant
Depression, Dementia, Choreiform movements
Caudate atrophy
↓ GABA and ACh in brain
20-50
Huntington gene on chromosome 4 with trinucleotide repeats (CAG) "Hunting 4 food"

Question 23

23

Marfan Syndrome
Inheritance
Mutation
Organs affected
Presentation
Risks associated with it?

Answer

Autosomal dominant
Fibrillin 1 gene mutation
Connective tissue of skeleton, heart, and eyes
Tall w/ long extremities, Hypermobile joints, long tapering fingers and toes (arachnodactyly)
Cystic Medial necrosis of the aorta --> aortic incompetence and dissecting aneurysm, Floppy Mitral Valve, Subluxation of the lenses

Question 24

24

Neurofibromatosis Type 1
Name
Inheritance
Findings
Chromosome

Answer

Von Recklinghausen's Disease
Autosomal dominant
Cafe-au-lait spots, Neural tumors, Lisch nodules (pigmented iris hamartomas)
Long arm of chromosome 17

Question 25

25

Neurofibromatosis Type 2
Inheritance
Presentation
Genetics with chromosome

Answer

Autosomal dominant
Bilateral acoustic schwannomas and Juvenile cataracts
NF2 gene on chromosome 22
"Type 2 = 22"

Question 26

26

von Hippel-Lindau disease
Inheritance
Findings
What are they at risk for?
Genetics with chromosome
PathoPhys

Answer

Autosomal dominant
Hemangioblastomas of retina/cerebellum/medulla
Multiple bilateral renal cell carcinoma and other tumors
Deletion of VHL gene (tumor suppressor) on chromosome 3p
Constitutive expression of HIF transcription factor and activation of angiogenic growth factor

Question 27

27

Cystic Fibrosis
Inheritance
Genetics with chromosome
PathoPhys with presentation
What happens to the protein

Answer

Autosomal recessive
Defect in CFTR gene on chromosome 7
Defective Cl channel --> secretion of abnormally thick mucus that plugs lungs, pancreas, and liver --> recurrent pulmonary infections (Pseudomonas and S aureus), chronic bronchitis, Bronchiectasis, Pancreatic insufficiency (malabsorption and steatorrhea leading to VitKADE deficiency), Nasal polyps, Meconium ileus
Abnormal folding --> degradation before reaching cell surface

Question 28

28

Normal function of CFTR

Answer

secretes Cl in lungs and GI tract and reabsorbs sweat

Question 29

29

Cystic Fibrosis
Male presentation
Infant presentation
Race affected
Diagnostic test
Treatment

Answer

Infertility in males due to bilateral absence of vas deferens
Failure to thrive in infants
Most common lethal genetic disease of whites
↑ concentration of Cl in sweat test
N-acetylcysteine to loosen mucous plugs (cleaves disulfide bonds within mucous glycoproteins)

Question 30

30

X Linked Recessive Disorders
Names
Presentation in females

Answer

"Be Wise, Fool's GOLD, Heeds Silly HOpe"
Bruton's agammaglobulinemia, Wiskott-Aldrich syndrome, Fabry's disease, G6PD deficiency, Ocular albinism, Lesch-Nyhan syndrome, Duchenne's (and Becker's) muscular dystrophy, Hunter's Syndrome, Hemophilia A and B, Ornithine transcarbamoylase deficiency
Female carriers may be affected and may have less severe symptoms due to random X chromosome inactivation

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Genetics Flashcards Preview

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Codominance DefinitionExample

Bole alleles contribute to the phenotype of the heterozygote Blood Group A, B, AB

Variable Expressivity Definition Example

Phenotype varies among individual with same genotype Neurofibromatosis type 1

Incomplete Penetrance Definition Example

Not all individuals with the mutant genotype show the mutant phenotype BRCA1 gene mutation do not always result in breast or ovarian cancer

PleiotropyDefinition Example

One gene contributes to multiple phenotypic effects PKU

Imprinting Definition Physiology Example

Differences in gene expression depend on whether the mutation is of maternal or paternal origin At some loci, only 2 allele is active depending on which parent it came from Prader Willi and Angelman's Syndrome

Anticipation Definition Example

Increased severity or earlier onset of disease in succeeding generations Huntington's Disease

Loss of Heterozygosity Definition Example

Two Hits needed for disease, born with one mutationRetinoblastoma and other tumor suppressors

Dominant Negative Definition Example

Heterozygote produces disease Nonfunctional TFs binding prevents wild-type from binding

Linkage Disequilibrium Definition Where is it measured

Tendency for certain alleles at 2 linked loci to occur together more often than expected by chance Measured in a population, not in a family, and often varies in different populations

Mosaicism Definition Where can it occur Example

Cells in the body differ in genetic make up due to post fertilization loss or change of genetic information during mitosisCan be germ-line which produces disease not carried by either parent's somatic cells Bone marrow stem cells --> hematologic mosaic. Fused zygote

Locus Heterogeneity Definition Example

Mutations at different loci can produce the same phenotype Marfan's, MEN2B, and Homocystinuria can all cause marfanoid habitus. Albinism

Heteroplasmy Examples

Presence of both normal and mutated mtDNA resulting in variable expression in mitochondrial inherited diseaseMyclonic Epilepsy

Uniparental disomy What is it?How do you tell when the error happened?

Offspring receives 2 copies of a chromosome from 1 parent and no copies from the otherHeterodisomy (heterozygous): Meiosis I error Isodisomy (homozygous): Meiosis II error or post zygotic loss of 1 chromosome and duplication of the other

Hardy-Weinberg Population Genetics EquationAssumptions In X linked recessive disease

(p^2) + 2pq + (q^2) = 1 and p+q=1No mutations, Selection, Migrations and random mating The frequency of an X linked recessive disease in males is q and in females is (q^2)

Prader-Willi Syndrome Chromosome Which allele is not expressed?What can cause it?Presentation

Inactivation or deletion on chromosome 15Paternal allele is not expressed Can also occur as a result of uniparental disomy Mental retardation, hyperphagia, obesity, hypogonadism, hypotonia

Angelman's Syndrome Chromosome Which allele is not expressed?What can cause it?Presentation

Inactivation or deletion on chromosome 15Maternal allele is not expressed Can also occur as a result of uniparental disomy Mental retardation, Seizures, Ataxia, Inappropriate laughter

Hypophosphatemic rickets PathoPhysPresentation Genetics

↑ Phosphate wasting in PT of kidney Rickets-like presentation X linked Dominant

Mitochondrial myopathies GeneticsPathoPhysPresentation Histo

Mitochondrial Inheritance Mutations affecting Mito function Myopathy and CNS disease (seizures) Muscle biopsy shows ragged red fibers

Familial Hypercholesterolemia AKAPathoPhysBlood test Heterozygotes vs Homozygotes Presentation Risk of what?

Hyperlipidemia Type IIAAbsent of defective LDL receptor Elevated LDL in blood Heterozygotes have cholesterol of 300Homozygotes have cholesterol of 700Severe atherosclerotic disease in early life. Tendon xanthoma (classically in the achilles tendon)MI may develop before age 20

Hereditary Hemorrhagic Telangiectasia AKAWhat organ system affected? How?Genetics Presentation

Osler-Weber-Rendu Syndrome Disorder of blood vessels with arteriovenous malformations Autosomal dominant Telangiectasia, Recurrent Epistaxis, Skin discoloration

Hereditary SpherocytosisInheritance What happens?MutationPresentation Treatment

Autosomal dominant Spheroid erythrocytes Spectrin or Ankyrin defective Hemolytic anemia, ↑ mean corpuscular hemoglobin concentration (MCHC)Splenectomy is curative

Huntington's Disease InheritancePresentation Gross PathoPhysAge of onset Genetics with chromosome and pathology

Autosomal dominant Depression, Dementia, Choreiform movementsCaudate atrophy↓ GABA and ACh in brain20-50Huntington gene on chromosome 4 with trinucleotide repeats (CAG) "Hunting 4 food"

Marfan Syndrome Inheritance Mutation Organs affectedPresentation Risks associated with it?

Neurofibromatosis Type 1NameInheritance Findings Chromosome

Von Recklinghausen's Disease Autosomal dominant Cafe-au-lait spots, Neural tumors, Lisch nodules (pigmented iris hamartomas)Long arm of chromosome 17

Neurofibromatosis Type 2InheritancePresentationGenetics with chromosome

Autosomal dominant Bilateral acoustic schwannomas and Juvenile cataractsNF2 gene on chromosome 22 "Type 2 = 22"

von Hippel-Lindau disease Inheritance Findings What are they at risk for?Genetics with chromosome PathoPhys

Autosomal dominant Hemangioblastomas of retina/cerebellum/medulla Multiple bilateral renal cell carcinoma and other tumors Deletion of VHL gene (tumor suppressor) on chromosome 3pConstitutive expression of HIF transcription factor and activation of angiogenic growth factor

Cystic Fibrosis Inheritance Genetics with chromosome PathoPhys with presentation What happens to the protein