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10 Cards in this Set
- Front
- Back
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Set 20 Q: Trinucleotide repeat disorder leading to the expansion of the FMR1 gene, leading to a defect in the long arm of the X chromosome, resulting in chromosomal breakage in vivo.
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Fragile X syndrome - this important genetic cause of mental retardation is second only to Down syndrome. Patients have distinctively long faces as well as a large mandibles, large ears, and large testicles (macro-orchidism) - Multiple CGG repeats in hypermethylation (think: "see" giant gonads)
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Set 20 Q: This condition results from a small deletion of chromosomal DNA on band 11 on the long arm of chromosome 22 (22p11)
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DiGeorge Syndrome - patients with this disorder present with Congenital heart defects due to aortic arch abnormalities, Abnormal facies, T-cell deficiencies, Cleft palate, and Hypocalcemia, which can be remembered with the acronym CATCH-22 - maldevelopment of 3rd pharyngeal pouch (inferior parathyroid and thymus) and 4th pharyngeal pouch (superior parathyroid) - tetany may result from hypocalcemia as a result of parathyroid aplasia
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Set 20 Q: This, the most common chromosomal disorder, is associated with maternal meiotic nondisjunction of chromosome 21
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Down Syndrome - its incidence is related to increased maternal age. Down Syndrome patients have increased incidence of ventricular septal defects, acute leukemias, and early onset Alzheimer Disease
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Set 20 Q: This condition results from the genetic deletion of DNA from the short arm (p) of chromosome 5
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Cri-du-chate (5p "cry of the cat") syndrome - these patients present with severe mental retardation, microcephaly, ocular hypertelorism (widspaced eyes) and an unusual cat-like cry
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Set 20 Q: This important tumor suppressor gene, a nuclear phosphoprotein, normally inhibits cell cycles progression at the G1/S boundary by inhibiting the transcription factor E2F
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Rb (retinoblastoma) - the Rb gene product nicely demonstrates Knudson's "two hit" hypothesis of tumor suppressor genes, in which patients inheriting one defective gene copy are more likely to develop tumors of the eye (retinoblastoma) and bone (osteosarcoma) as they must only undergo one additional mutation. Normal individuals must undergo separate mutations in both alleles in the same tissue for sporadic tumors to occur.
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Set 20 Q: Should cytochrome c be released from the outer membrane of the mitochondria in response to changes in membrane permeability, this antiapoptotic gene functions by inhibiting the irreversible cascade of apoptosis.
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bcl-2 - cytochrome c is capable of activating programmed cell death. Various cancers, such as follicular lymphomas , are associated with over expression of bcl-2 and the development of cancer as a result of impaired apoptosis. - Cytochrome c is normally cut out of mitochondrial membrane by BAX proteins. bcl-2 inhibits BAX proteins and APAF-1.
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Set 20 Q: Mutation in these tumor suppressor genes, involved in DNA repair, are associated with familial clustering in the development of breast and ovarian cancer.
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BRCA-1 and BRCA-2 - although familial forms of breast cancer account for only 5-10% of all breast cancer cases, mutations in thee two genes are associated with 80% of familial cases. Therefore the presence of breast cancer in a first-degree relative requires consideration as a risk factor in the development of breast cancer.
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Set 20 Q: Mutations in this gene, located on chromosome 5, lead to loss of intracellular adhesiveness and the development of multitudes of precancerous polyps in the colon.
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APC (adenomatous polyposis coli) - this autosomal dominant condition gives rise to thousands of precancerous polyps in the colon, and one polyp or more will undergo malignant transformation, resulting in the development of colon cancer. - HNPCC is autosomal recessive
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Set 20 Q: This disorder results from defects in the mismatch repair genes during DNA replication, allowing erroneous base pairing between nucleotide bases, with the accumulation of mutations on several genes over time.
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HNPCC (hereditary non-polposis colon cancer) syndrome - individuals with this autosomal recessive condition have an increased tendency to develop familial carcinomas of the colon. - nucleotide mismatch that escapes proof-reading
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Set 20 Q: This disorder results from mutations in the tumor suppressor gene p53, which is often referred to as the "guardian of the genome," since p53 senses DNA damage, triggers cell cycle arrest and DNA repair, or triggers apoptosis in the event that the damage is too severe.
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Li Fraumeni Syndrome - this disorder is characterized by an increased tendency to develop sarcomas, breast cancer, leukemias, and brain tumors at a young age. The p53 gene is the one most commonly mutated in cancer, giving rise to nearly 50% of all sporadic tumors
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