Epigenetics

Question 0

Epigenome

Answer 0

Consists of chemical compounds that modify, or mark, the genome in a way that tells it what to do, where to do it and when to do it. The marks, which are not part of the DNA itself, can be passed on from cell to cell as cells divide, and from one generation to the next

Question 1

CpG island

Answer 1

Stretches of DNA several hundred to several thousand base pairs long with an increased density of the CpG dinucleotide sequence. In humans there are about 45,000 CpG islands, mostly found at the 5’ ends of the genes. They are unmethylated except for those on the inactive X chromosome and some associated with imprinted genes

Question 2

DNA methylation

Answer 2

Epigenetic mark that is repressive. It plays role in embryonic development, x inactivation, transposon suppression, genomic imprinting. Primarily found in 5’-CpG-3’ dinucleotide, which is a palindrome so the opposite strand is also methylated

Question 3

TET proteins

Answer 3

Act as DNA methylation erasers. They alter the 5-methylcytosines to other related forms that get recognized by the DNA repair machinery and subsequently reverted back to cytosine

Question 4

Monoallelic gene expression

Answer 4

Occurs only when one of the two homologous alleles of a gene is expressed. Classic example is x inactivation

Question 5

Genomic imprinting

Answer 5

Only one allele of a gene is expressed, depending on the parental origin of the allele

Question 6

Uniparental disomy

Answer 6

Person receives two copies of a chromosome or part of a chromosome from one parent and no copies from the other parent

Question 7

Prader-Willi syndrome

Answer 7

Chromosome 15q11.2-q13 contains multiple genes that contain maternal and paternal imprints. Characterized by excessive eating and gradual development of morbid obesity, cognitive impairment, and strabismus (eye direction misalignment). Caused by loss of paternal copies of the genes in this region

Question 8

Angelman syndrome

Answer 8

Characterized by developmental delays, mental retardation, ataxia, frequent smiling and laughter, and excitable personality. Disruption of the paternally imprinted UBE3A located within 15q11.2-q13 region. Caused by loss of maternal copies of the genes in this region