final - epigenetics

Question 1

name three types of epigenetic change

Answer 1

• DNA methylation
• histone modication
• siRNAs

Question 2

explain the differences between active and silent in histone modification

Answer 2

active: (euchromatin) unmethylated cytosine, acetylated histones
silent: (heterochromatin) methylated cytosine, deacetylated histones

Question 3

methylation is mediated by

Answer 3

DNA methyl transferases

Question 4

which nucleotides are methylated?

Answer 4

99 percent of the time it’s cytosine (C) when it follows guanine (G)

Question 5

what are CpG islands and what do they do?

Answer 5

• places on DNA where CG dinucleotides are abundant
• first exon of gene
• switch to silence gene downstream from it when methylated

Question 6

what is the mechanism of action of methyl groups

Answer 6

• bind to DNA and project into major groove
• displace transcription factors
• attract methyl-binding proteins associated with gene silencing and chromatin compaction

Question 7

give some examples of diseases caused by genomic imprinting

Answer 7

• chromosome 15q11-q13: paternal is prader will and maternal is angelman
• fragile X syndrome: x-linked CGG repeat disorder,

Question 8

symptoms of prader will

Answer 8

mental retardation, short stature, hypotonia, hyperphagia, obesity, small hands and feet, hypogonadism

Question 9

symptoms of angelman

Answer 9

mental retardation, ataxic gait seizures, inappropriate laughter “happy puppets”

Question 10

symptoms of fragile X syndrome

Answer 10

• most common mental retardation after down’s syndrome

- Macro-orchidism, ASDs, characteristic face structure, hyper-extendible finger joints; epilepsy; mitral valve prolapse

Question 11

what gene is involved in fragile x syndrome

Answer 11

• FMR-1, familial mental retardation-1

Question 12

how does CpG hyper methylation increase cancer risk?

Answer 12

• oncogene activation

- inactivation of tumor suppressors

Question 13

is MGMT hypermethylation a good prognostic tool?

Answer 13

No, but status can act as a marker for alkylating agents, which is a better prognostic tool

Question 14

connect mismatch repair proteins to cancer

Answer 14

• 15% of colorectal cancers have inactivation of MMR system
• HNPCC - methylation of one allele
• sporadic colorectal cancer - both alleles

Question 15

types of cancer associated with MGMT hypermethylation

Answer 15

• gliomas
• non-small cell lung cancer
• head and neck tumors
• colorectal cancer

Question 16

renal cell carcinoma is associated with what cancer causing epigenetic process?

Answer 16

miRNA

Question 17

what are the three types of renal cell carcinoma?

Answer 17

• clear cell
• papillary
• chromophobe

Question 18

how is miRNA useful in diagnosis?

Answer 18

• can help to distinguish subtypes of renal cell carcinoma

Question 19

what miRNA pathway is an important driver in the development of RCC?

Answer 19

miR-210