Biochemistry - Genetics Flashcards
Which traits are codominantly expressed ?
ABO blood type, alpha-1-antitrypsin deficiency
What is incomplete penetrance?
Possessing a mutant genotype doesn’t guarantee a mutant phenotype
What is pleiotropy?
1 gene mutation can have multiple phenotypic effects
What is genetic anticipation?
Increasing severity or earlier onset of disease in successive generations (TNR diseases)
Give an example of loss of heterozygosity
Somatic retinoblastoma, Lynch syndrome, Li-Fraumeni (inherit one bad, one good copy, one good copy must be lost for bad to show)
Linkage disequilibrium
Tendency of two genes close on a loci to occur together more or less often than by chance. Measured in population s
What is somatic mosaicism
Genetically distinct cell line in individual that arises from mitotic errors after fertilization and propagates through multiple tissues or organs
Gonadal mosaicism
Mutation only in egg or sperm cells (mutation may show in offspring but not parent)
What is McCune Albright syndrome?
Mutation of G-protein signaling pathway. Presents as unilateral cafe-au-lait spots, polyostic fibrous dysplasia, precocious puberty, multiple endocrine endocrine abnormalities
When is McCune Albright syndrome lethal?
When mutation occurs before fertilization
Which part of collagen synthesis is Vitamin C necessary?
Hydroxylation of specific proline and lysine residues
Which diseases occur from defects in cross-linking collagen?
Ehler-Danlos, Menkes
What is heterodisomy?
When a child inherits both sets of chromosomes from a single parent (both of their homologous chromosomes). Error in Meiosis I.
What is Isodosomy?
When a child inherits two identical copies of a single chromosome that duplicated itself from one parent. Error in meiosis II or postzygotic chromosomal duplication
What are the four assumptions for Hardy-Weinberg equilibrium?
No mutations
No natural selection
No net migration
Random mating
What is the formula for Hardy-Weinberg?
p^2+2pq+q^2 = 1
Describe the etiology of Prader-Willi syndrome
Maternal gene is imprinted (silenced). Paternal gene is deleted/mutated.
Clinical presentation of Prader-Willi Syndrome
Hyperphagia, obesity, retardation, hypogonadism, hypotonia
Etiology of Angelman syndrome
Paternal gene imprinted (silenced). Deletion/mutation of maternal gene
Clinical presentation
Inappropriate laughter, seizures, ataxia, severe intellectual disability
Which chromosome is affected in Angelman and Prader-Willi syndrome?
Chromosome 15
What is the cause of Prader-Willi syndrome in 25% of cases?
Maternal uniparental disomy (child inherits both silenced maternal genes)
What is the defect in most autosomal dominant diseases?
Defective structural gene
What is critical for diagnosing autosomal dominant disorder?
Family history
