14. Epigenetic Inheritance & Imprinting

Question 0

epigenome

Answer 0

range of modifications that are imposed on the genome and ensure the stable transmission of gene expression patterns without changes to the DNA sequence

Question 1

epigenetics

Answer 1

information passed from one generation to the next but not encoded in DNA

Question 2

epigenetic disruptor

Answer 2

chemicals, toxins, or environmental compounds that can cause disruptions to epigenome

Question 3

epimutation

Answer 3

mutations in the epigenome that result in incorrect imprinting or passage

Question 4

methylation

Answer 4

common alteration in vertebrates that causes a cytosine (in a CG sequence) to be methylated, creating a 5-methylcytosine

is passed on during DNA replication

Question 5

maintenance methyltransferases

Answer 5

will recognize methylation patterns & make sure after DNA replication that new strands are properly methylated

contributes to stability of gene repression, also called epigenetic silencing

Question 6

housekeeping genes

Answer 6

associated by GC rich areas (GC islands)

that are maintained on active genes and non-methylated

Question 7

what happens to methylated CG sequences?

Answer 7

they are selectively lost due to deamination of 5-methylcytosine converting it to thymidine & therefore changing the opposite strand base pair to an adenine instead of the original guanine

Question 8

what does DNA imprinting do in terms of variation?

Answer 8

increases variation

Question 9

genetic conflict hypothesis

Answer 9

states that male & female evolutionary goals are different in terms of reproduction

males want large offspring
females want smaller offspring (less physiologically taxing)

Question 10

example of an imprinted gene?

Answer 10

insulin growth factor 2

Question 11

insulin growth factor 2 parental genes

Answer 11

mom: IGF2 receptor ON; IGF2 OFF
dad: IGF2 receptor OFF; IGF2 ON

Question 12

delete mother’s IGF2 receptor gene?

Answer 12

father’s receptor gene on

results in large offspring

Question 13

delete father’s growth factor gene?

Answer 13

mother’s growth factor gene on

dwarf offspring produced

Question 14

deleting mother’s IGF2 receptor gene and father’s IGF2 gene results in?

Answer 14

normal sized offspring

Question 15

epimutation examples (4)

Answer 15

1. prader-willi
2. anglemanns
3. beckwith-wiedemann
4. NOEY2

Question 16

prader-willi syndrome

Answer 16

paternal inheritance of deletion

characterized by hypotonia, obesity, & hypogonadism

Question 17

angelmann

Answer 17

maternal inheritance of deletion

characterized by epilepsy, tremors, perpetually smiling facial expression

Question 18

beckwith-wiedemann syndrome

Answer 18

overgrowth disorder present at birth and characterized by increased risk of cancer & congenital features

Question 19

NOEY2

Answer 19

ras-like paternally expressed imprinted gene on chromosome 1 tumor suppressor for breast & ovarian cancer

by losing expression of this gene, you have an increased risk of these cancers

can be caused in rare cases when both copies of the gene are inherited from the mother (uniparental disomy)

Question 20

rat epigenetic study: high fat diet (HFD)

Answer 20

significant weight gain
increased leptin & insulin
insulin resistance

Question 21

rat epigenetic study: paternal high fat diet (HFD)

Answer 21

alters female offspring expression of 77 genes

I1132ra2 was upregulated
reduced methylation–>overexpression

Question 22

rat epigenetic study: undernourished diet

Answer 22

rats show changes in promoter methylation & gene expression

results in undermethylation & overexpression of PPAR-alpha (increased production of ketone bodies)
increase GC receptors

Question 23

undernourished female rats produced offspring that were…?

Answer 23

more likely to be overweight

Question 24

in vitro fertilization

Answer 24

greater risk of low birth weight, birth defects, disorders associated w/lower mean methylation in placental sites & higher mean methylation in cord blood

Question 25

trans-epigenetic signals

Answer 25

when a gene expresses a product that has positive feedback on the gene itself and is transmitted by a partition of cytosol with a positive feedback loop

Question 26

example of trans-epigenetic signals

Answer 26

protein product that enhances the gene activity

Question 27

cis-epigenetic signals

Answer 27

when a gene product alters DNA inherited via chromosome segregation during cell division

Question 28

cis-epigenetic signals example

Answer 28

product plays a role in histone modification

Question 29

conformational change to aggregated state example

Answer 29

prions can survive replication in aggregation state (misfolded protein) and will also be inherited

Question 30

what can explain why identical twins or cloned animals are not exactly the same or the rising obesity rates?

Answer 30

epigenetics

Question 31

x-chromosome inactivation

Answer 31

(barr body)
because females have 2 X chromosomes, various techniques are used to express that same amount of transcription as males (DOSAGE COMPENSATION)

Question 32

how is dosage compensation achieved in mammals?

Answer 32

by inactivating one of the two chromosomes in all somatic cells

chromosome that is inactivated is coated with Polycomb complex to help silence expression

Question 33

non-mammal examples of dosage compensation

Answer 33

1. drosophila (genes on male X chromosome expressed at 2-fold levels)
2. nematodes: genes on hermaphrodite’s 2 X chromosomes are expressed at half the levels of the male