genetics post midterm Flashcards
Philadelphia chromosome
t (9;22) -> activation of abl proto-oncogene in hematopoietic cells, results in chronic myelogenous leukemia
Burkitt’s lymphoma
t (8;14)
Wolf-Hirschhorn syndrome
Del 4p - large deletion. Facial anomalies (widely-spaced eyes), prominent nose, abnormal iris, cardiac anomalies, mental and developmental delay
Cri-du-chat
Del 5p. 46, XX, del(5p) or 46 XY del(5p).
High-pitched, cat-like cry. Mental retardation, speech problems. Microcephaly
Dx with FISH, CGH, karyotype banding studies
Velocardiofacial syndrome (DiGeorge syndrome)
Microdeletion in chromosome 22q. Congenital heart defects, absence of thymus (thymic aplasia), cleft lip and palate, facial anomalies (narrow palpebral fissures, prominent nasal root), learning disability.
Dx with FISH
Angelman and Prader Willi syndromes
Angelman syndrome - deletion of maternal chromosome 15
Prader Willi syndrome - deletion of paternal chromosome 15
WAGR syndrome
Wilms’ tumor, aniridia, genitourinary malformations, and retardation of growth and development. Del(11p13). LOF of WT1 gene on chromosome 11 -> encodes TF important in control of cell growth and differentiation
Dx with FISH - shows failure of PAX6 locus specific probe
Yellow agouti (Ay) mutation
Interferes with a-MSH binding to melanocortin receptor, which is involved in food intake regulation
obese (ob) mutation
Defect in leptin protein (satiation signal)
diabetes (db) mutation
Defect in leptin protein receptor
fat mutation
Defect in fat transport across membranes
tubby mutation
Defect in upstream signaling molecules (transcription factor
MC4R mutation
Defect in melanocortin 4 receptor, a member of the rhodopsin family of G-protein receptors. Autosomal dominant
Chronic myeloid leukemia
Philadelphia translocation (9;22) (p210;p160)-> hybrid Bcl-Abl protein
Imatinib mesylate (ST1571)
Powerful tyrosine kinase inhibitor specific for a few TKs including ABL -> very effective against BCR/ABL fusion gene (against Ph+ chronic myeloid leukemia). ABL is stuck in its activated form -> imatinib binds to the tyrosine kinase active site and prevents its activity
Bloom syndrome
Autosomal recessive. Defect in BLM gene (15q26.1) = RecQL3 DNA helicase required for replication repair, recombination. Chromosomal instability resulting in many chromosomal breaks and sister chromatid exchanges. High incidence of cancer of a broad range of types
Smaller than average, narrow chin, prominent nose and ears, facial rash (pigment and dilated blood vessels) upon exposure to sun; often get diabetes and have neurological, lung, and immune system deficiencies
Ataxia telangiectasia
Autosomal recessive cancer
Xeroderma pigmentosum
Autosomal recessive, mutations in 9 NER (nucleotide excision repair) genes. Clinical sun sensitivity - sunburn, blistering, freckled with hyperpigmented skin lesions. Ocular involvement - conjunctivitis, ocular tumors. 1000-fold increase in skin cancer including melanomas. DNA dmg is cumulative and irreversible
Fanconi anemia
Autosomal recessive cancer
Dysplastic nevus syndrome
Precursor to malignant melanoma. Inherited mutation in p16 (INK4A) CDK inhibitor
Li-Fraumeni
Inherited mutation in p53-> increased risk for breast, bone, brain cancers, adrenocortical tumors, soft-tissue carcinomas. Cancer appears at young age
Familial adenomatous polyposis
Mutations in the APC (adenomatous polyposis coli, “gatekeeper”) gene on chromosome 5 (5q21). Multiple (>100) adenomatous polyps develop in distal colon that SLOWLY progress to cancer. APC is normally tumor suppressor that phosphorylates B-catenin in absence of WNT -> ubiquitination and B-catenin degradation.
Mutation in B-catenin (unable to be phosphorylated) gives similar results -> no WNT needed to trigger growth
Hereditary non-polyposis colon cancer (HNPCC)/Lynch syndrome
Mutation in DNA MMR (“caretaker”, like RAS, p53) genes -> accumulate mutations RAPIDLY, tumors have microsatellite instability
Breast/ovarian cancer
Mutation in BRCA1 - breast, BRCA2 - ovarian. Pancreatic and other cancers also more common. BRCA1 and 2 involved in DNA repair or apoptosis when DNA can’t be repaired.
HER-2
Overexpressed in sporadic breast cancer. Is gene for growth factor rec -> get double minute chromosomes
Tx: Herceptin drug (Ab) -> binds to HER2 and prevents binding of EGF to HER2. Very effective for HER2+ tumors, useless for HER2- tumors
Alzheimers dz
Evidence for DNA fragmentation int he brain cells of AD pts. Proapoptotic Bak and Bad protein levels increased (antiapoptotic proteins Bcl-2 and Bcl-xL also increased, perhaps compensatory response in surviving neurons). APP, PS1, and PS2 proteins are cleaved by caspase-3. Neuronal caspase-3 immunoreactivity increased
