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Genetics

First Aid - Biochem - Genetics

QuestionAnswer
variable expression nature and severity of phenotype vary from 1 person to another - ex. 2 patients with neurofibromatosis may have varying dz. severity
incomplete penetrance not all individuals with a mutant genotype show the mutant phenotype
pleiotropy 1 gene has multiple effets on an individual's phenotype - ex. PKU causes many seemingly unrelated sx. ranging from mental retardation to hair and skin changes
anticipation severity of dz. worsens or age of onset of dz. is earlier in succeeding generations - ex. huntington's dz.
loss of heterozygosity pt. inherits or develops a mutation in a tumor suppressor gene, the complementary allele must be deleted/mutated before cancer develops - this is not true of oncogenes (can lose 1 and still function?) - retinoblastoma
dominant negative mutation exerts a dominant effect - heterozygote produces nonfunctional altered protein that also prevents the normal gene product from functioning -mutation of TF in its allosteric site, nonfunctioning mutant can still bind DNA and prevent nml TF binding
Hardy-Weinberg Law assumes no mutation at locus, no selection for any genotypes, completely random mating, and no migration
Hardy-Weinberg equations dz. prevalence = p2 + 2pq + q2 =1 allele prev. = p + q = 1 heterozygote prev. = 2pq (x linked recessive males = q/females = q2)
Autosomal dominant disease examples familial adenomatous polyposis, marfan's syndrome
Autosomal recessive disease examples PKU, sickle cell, thalassemias, CF
X-linked recessive disorder examples G6PD, Lesch-Nyhan
Trinucleotide repeat expansion disease example Fragile-X syndrome
Autosomal trisomy disease example Down syndrome
Deletion syndrome examples Cri du chat, DiGeorge (22q11)
Familial adenomatous polyposis colon becomes covered with polyps > colon cancer, deletion on chromosome 5 (APC gene)
Cri du chat congenital microdeletion of short arm of chromosome 5, microcephaly, mental retardation, high pitched crying/mewing, epicanthal folds, cardiac abnormalities
Created by: Smukadam