Lecture 25

Question 1

Nijmegen Breakage Syndrome (NBS)

Answer 1

• NBN gene mutations lead to defective HR (double-stranded repair)
• bird-like faces
• microcephaly

Question 2

Bloom Syndrome (BS)

Answer 2

• BLM mutation leads to abnormal DNA helicase -> replication errors
• defective HR, increased frequency of sister chromatid exchange
• type 2 diabetes, butterfly-shaped rash on face after sun exposure

Question 3

Fanconi Anemia (FA)

Answer 3

• Fanconi gene mutations lead to double-stranded DNA repair defect (faulty HR)
• bone marrow failure and skeletal malformations

Question 4

Xeroderma pigmentosum (XP)

Answer 4

• mutations in one of at least 9 genes leads to faulty NER
• from UV-induced damage so pyrimidine dimers are formed
• freckled hyperpigmentation with sun exposure
• severe photosensitivity
• malignant tumor development

Question 5

Familial Adenomatous Polyposis (FAP2) OR MUTYH-associated Polyposis (MAP)

Answer 5

• MYH glycosylase aids DNA repair by correcting DNA replication
• defective base excision repair
• colonic adenomatous polyps and increased risk of colorectal cancer

Question 6

Hereditary Nonpolyposis Colorectal Cancer (HNPCC)

Answer 6

also called Lynch syndrome

• DNA mismatch repair
• increased risk of cancer
• microsatellite instability
• main feature is colorectal cancer, but predisposed risk for other cancers as well

Question 7

Ataxia Telangiectasia (ATM)

Answer 7

• ATM gene codes for a serine/threonine protein kinase
• repairs breaks in double-stranded DNA through basic mechanism
• could lead to cell death in the cerebellum if severe
• symptoms: cerebellar ataxia (sensory-motor neuropathy), immunodeficiency, oculomotor apraxia, telangiectasia (dilated blood vessels in eyes)

Question 8

Severe Combined Immunodeficiency Disease (SCID)

Answer 8

• several genes involved in NHEJ repair
• decreased immune response, inability to fight infection