epigenetics

Question 1

define epigenetics

Answer 1

all the processes that lead to heritable changes in gene expression as cells divide

Question 2

is the genome static or flexible?

Answer 2

static

Question 3

is the epigenome static or flexible?

Answer 3

flexible

Question 4

what is the barker hypothesis?

Answer 4

the environment that a fetus faces in utero affects their risk of developing disorders in later life

Question 5

what are the 4 types of epigenetic mechanisms?

Answer 5

DNA methylation
micro and small RNAs
chromatin architecture
histone modification

Question 6

does DNA methylation activate or inactive a gene?

Answer 6

inactivates it

Question 7

explain the process of DNA methylation

Answer 7

methyl group adds to cytosines immediately adjacent to guanines (e.g. CpG islands in promoter regions) using DNA methyltransferase

Question 8

how does DNA methylation cause gene silencing?

Answer 8

methyl group stops RNA polymerase II from binding

stops transcription factors from binding to the promoter region

Question 9

what are CpG islands?

Answer 9

areas rich in C and G in the promoter region

Question 10

how do micro and small RNAs cause gene silencing?

Answer 10

miRNA binds to complementary regions on the DNA so ribosomes cant attach and translate
can induce degradation of mRNA

Question 11

what changes in the shape of the histone can take place?

Answer 11

sliding
ejection
H2A-H2B dimer ejection or replacement

Question 12

what are the main types of post-transcriptional histone modifications?

Answer 12

acetylation
methylation
phosphorylation
ubiquitination

Question 13

what amino acid does modifications of histones occur on?

Answer 13

lysine

Question 14

what does histone acetylase do?

Answer 14

catalyses the transfer of acetyl group onto lysine

Question 15

how does acetylation affect a histone?

Answer 15

makes the promoter more accessible for transcription

Question 16

what does histone deactylase do?

Answer 16

reverses the process of adding an acetyl group on

Question 17

how does hypomethylation play a role in the development of cancer?

Answer 17

less methylation
less silencing
more room for tumours to form

Question 18

what is imprinting?

Answer 18

the preferential expression of either the paternal or maternal allele

Question 19

name imprinting related disorders and how they’re caused

Answer 19

part of chromosome 15 deleted
Prader-Willi - allele from father
Angelman - allele from mother

Question 20

define genome

Answer 20

The complete set of genes / genetic material present in a cell or organism

Question 21

define epigenome

Answer 21

the parts of the genome that are actually used

Question 22

what does low availability of nutrients in prenatal stage followed by improvement in nutritional availability in childhood cause?

Answer 22

metabolic disorders e.g. diabetes type 2, obesity, coronary heart disease

Question 23

what is a nucleosome?

Answer 23

DNA wrapped around a histone

Question 24

how does DNA packing prevent gene expression?

Answer 24

prevents transcription proteins from accessing DNA

Question 25

how does chromatin architecture affect DNA expression?

Answer 25

- Alter the contact between DNA and histones - Alter the path of the DNA as it winds around the histones - Alter the structure of the nucleosome core itself

Question 26

what does histone acetylation do?

Answer 26

opens chromatin DNA accessible transcription activated

Question 27

what does histone deactylation do?

Answer 27

closed chromatin DNA inaccessible transcription repressed

Question 28

what are HDAC inhibitors?

Answer 28

used to increase gene transcription for some genetic conditions

Question 29

what does genome wide hypomethylation occur with?

Answer 29

ageing and tumourgenesis

Question 30

what is non-coding RNAs?

Answer 30

functional RNA but not translated into proteins

Question 31

what causes Prader Willi syndrome? how does it present?

Answer 31

deletion of PATERNAL copy of chromosome 15q11 q13 leads to language, motor and developmental delays, excessive weight gain

Question 32

what causes Angelman syndrome? how does it present?

Answer 32

deletion of MATERNAL copy of chromosome 15q11q13 severe mental retardation, happy demeanor, non-verbal

Question 33

what are epigenetic therapies?

Answer 33

HDAC inhibitors DNMT inhibitors Non-coding RNA Osteopathic manipulation

Question 34

how does reducing calorie lead to increased lifespan?

Answer 34

works by maintaining degree of methylation