Codominance
Definition
Example
Bole alleles contribute to the phenotype of the heterozygote
Blood Group A, B, AB
Key Terms
Codominance
Definition
Example
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
Pleiotropy
Definition
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 ...
Anticipation
Definition
Example
Increased severity or earlier onset of disease in succeeding generations
Huntington’s Disease
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| Term | Definition |
|---|---|
Codominance | Bole alleles contribute to the phenotype of the heterozygote |
Variable Expressivity | Phenotype varies among individual with same genotype |
Incomplete Penetrance | Not all individuals with the mutant genotype show the mutant phenotype |
Pleiotropy | One gene contributes to multiple phenotypic effects |
Imprinting | Differences in gene expression depend on whether the mutation is of maternal or paternal origin |
Anticipation | Increased severity or earlier onset of disease in succeeding generations |
Loss of Heterozygosity | Two Hits needed for disease, born with one mutation |
Dominant Negative | Heterozygote produces disease |
Linkage Disequilibrium | Tendency for certain alleles at 2 linked loci to occur together more often than expected by chance |
Mosaicism | Cells in the body differ in genetic make up due to post fertilization loss or change of genetic information during mitosis |
Locus Heterogeneity | Mutations at different loci can produce the same phenotype |
Heteroplasmy | Presence of both normal and mutated mtDNA resulting in variable expression in mitochondrial inherited disease |
Uniparental disomy | Offspring receives 2 copies of a chromosome from 1 parent and no copies from the other |
Hardy-Weinberg Population Genetics | (p^2) + 2pq + (q^2) = 1 and p+q=1 |
Prader-Willi Syndrome Chromosome Which allele is not expressed? What can cause it? Presentation | Inactivation or deletion on chromosome 15 |
Angelman's Syndrome Chromosome Which allele is not expressed? What can cause it? Presentation | Inactivation or deletion on chromosome 15 |
Hypophosphatemic rickets | ↑ Phosphate wasting in PT of kidney |
Mitochondrial myopathies Genetics PathoPhys Presentation Histo | Mitochondrial Inheritance |
Familial Hypercholesterolemia AKA PathoPhys Blood test Heterozygotes vs Homozygotes Presentation Risk of what? | 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 |
Hereditary Hemorrhagic Telangiectasia AKA What organ system affected? How? Genetics Presentation | Osler-Weber-Rendu Syndrome |
Hereditary Spherocytosis Inheritance What happens? Mutation Presentation Treatment | Autosomal dominant Spheroid erythrocytes Spectrin or Ankyrin defective Hemolytic anemia, ↑ mean corpuscular hemoglobin concentration (MCHC) Splenectomy is curative |
Huntington's Disease Inheritance Presentation Gross PathoPhys Age of onset Genetics with chromosome and pathology | 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” |
Marfan Syndrome Inheritance Mutation Organs affected Presentation Risks associated with it? | Autosomal dominant |
Neurofibromatosis Type 1 Name Inheritance Findings Chromosome | Von Recklinghausen’s Disease |
Neurofibromatosis Type 2 | Autosomal dominant |
von Hippel-Lindau disease Inheritance Findings What are they at risk for? Genetics with chromosome PathoPhys | Autosomal dominant |
Cystic Fibrosis Inheritance Genetics with chromosome PathoPhys with presentation What happens to the protein | Autosomal recessive |
Normal function of CFTR | secretes Cl in lungs and GI tract and reabsorbs sweat |
Cystic Fibrosis Male presentation Infant presentation Race affected Diagnostic test Treatment | Infertility in males due to bilateral absence of vas deferens |
X Linked Recessive Disorders | "Be Wise, Fool's GOLD, Heeds Silly HOpe" |
Duchenne's Muscular Dystrophy Inheritance Mutation PathoPhys Presentation Time of onset Risk of what? Diagnosis | X linked recessive Frameshift mutation of dystrophin gene Accelerated muscle breakdown Weakness begins in pelvic girdle muscles and progresses superiorly. Pseudohypertrophy of calf muscle. Use of Gower's Maneuver requiring assistance of upper extremities to stand up Onset before 5 years of age Risk of Cardiac Myopathy ↑ CPK and muscle biopsy |
Becker's Muscular Dystrophy Inheritance Mutation Severity Onset Diagnosis | X linked mutated dystrophin gene |
Fragile X syndrome Inheritance Mutation PathoPhys Frequency Findings | X linked Trinucleotide repeat disorder (CGG) Defect affecting methylation and expression of FMR1 gene 2nd most common cause of mental retardation after Down syndrome Macroorchidism (enlarged testes), Long face with Large jaw, Large everted ears, Autism, MVP |
Longest human gene | Dystrophin gene | High rate of spontaneous mutation |
Function of Dystrophin | Helps anchor muscle fibers, primarily in skeletal and cardiac muscle |
Trinucleotide Repeat Expansion Diseases | "Try Hunting for My Fried Eggs" "X-Girlfriend's First Aid Helped Ace My Test" Fragile X: CGG Friedreich's ataxia: GAA Huntington's: CAG Mytonic dystrophy: CTG Shows anticipation |
Down Syndrome AKA Frequency Findings What are they at risk for? | Trisomy 21 ("Drinking Age is 21") |
Down Syndrome | 95% due to meiotic nondisjunction of homologous chromosomes (advanced maternal age) |
Edward's Syndrome AKA Findings What are they at risk for? Course Diagnosis | Trisomy 18 ("Election age is 18") |
Patau's Syndrome AKA Presentation What are they at risk for? Course Diagnosis | Trisomy 13 ("Puberty 13") |
Non disjunction in meiosis I | 2 homologous chromosomes in 2 cells, Missing chromosome in 2 cells |
Non disjunction in meiosis II | 2 identical chromosomes in 1 cell, 2 normal cells, 1 cell missing a chromosome |
Robertsonian Translocation | Nonreciprocal translocation. Fusion of 2 acrocentric chromosomes and loss of short arms |
Cri-du-chat Syndrome | Congenital microdeletion of short arm of chromosome 5 Microcephaly, Mental Retardation, High pitched crying (mewing), Epicanthal folds Cardiac Abnormalities (VSD) |
William's Syndrome | Congenital microdeletion of long arm of chromosome 7 (including elastin gene) |
22q11 Deletion Syndrome | "CATCH 22" |