3/20 Regulation

Question 1

how is chromatin compaction relevant to gene regulation in eukaryotes?

Answer 1

tightly compacted chromatin (closed) are unavailable for gene expression and must be opened or loosed in order to be transcribed

Question 2

do prokaryotes have chromatin compaction as a part of their gene regulation?

Answer 2

no, they do not have nucleosomes

Question 3

by what mechanism does chromatin remodeling occur

Answer 3

transcriptional activators orchestrate changes through ATP-dependent chromatin remodeling

Question 4

what are the four methods of chromatin remodeling

Answer 4

1) change the relative position of a few nucleosomes

2) change the overall nucleosome spacing

3) remove/ evict histone

4) replacement of histone variant

Question 5

what are histone variants

Answer 5

they are members of the histone gene family that have independently accumulated mutations over time

Question 6

why are histone variants relative to chromatin structure

Answer 6

they are incorporated into nucleosomes and affect compaction

Question 7

What is HI° histone

Answer 7

it facilitates chromatin compaction and decreases gene expression

Question 8

what is H2A. Bd histone

Answer 8

it converts heterochromatin into euchromatin and increases gene expression

Question 9

what is cenH3 histone

Answer 9

it facilitates compaction of the centromere

Question 10

what is macroH2A histone

Answer 10

it inactivates specific X chromosomes in females

Question 11

how do histone variants affect gene expression

Answer 11

they can increase it or decrease it depending on the variant

Question 12

true or false

histone variants have arisen due to gene duplication events and will increase gene activity when they are substituted into the chromatin structure

Answer 12

false, they may decrease gene activity as well

Question 13

what is epigentic modifications

Answer 13

changes in gene expression without changing the bases

Question 14

what is a histone tail

Answer 14

it is a tail of aminoacids on the histone

Question 15

how does the histone tail affect gene expression?

Answer 15

the amino terminal can be modified

Question 16

what are the three forms of histone tail modificaitons

Answer 16

acetylation, phosphorylation, and methylation

Question 17

what is the amino terminal made up of on the histone tail?

Answer 17

it has positively charged amino acids that can associate with DNA

Question 18

How do the addition of acetyl groups (acetylation) affect chromatin compaction

Answer 18

they loosen it and allow it to ope by interfering with the charge interactions between he DNA and the histone

Question 19

histone modifications in general have what effect on chromatin structure

Answer 19

they can open or close it

Question 20

are histone tail modifications reversible

Answer 20

yes lol

Question 21

what is DNA methylation

Answer 21

it is the methylation of cytosines in eukaryotes

Question 22

what effect does DNA methylation have on eukaryotes?

Answer 22

it silences gene expression

Question 23

what is the overall affect of cpG regions?

Answer 23

they are focal points for methylation by methylases

Question 24

How does DNA methylation affect transcription?

Answer 24

it silences/ inhibits transcription

Question 25

if a housekeeping gene has a CpG island, will it be methylated?

Answer 25

no, it will be unmethylated and constitutively made

Question 26

in tissue-specific genes, will CpG island be methylated

Answer 26

yes they can be methylated and silenced according to their gene expression

Question 27

if you have increased, methylation, what happens to the gene expression?

Answer 27

it is decreased

Question 28

if you have decreased methylation, what happens to the gene expression

Answer 28

it is increased

Question 29

what are the two ways that methylation can affect transcription factors

Answer 29

it can block their binding and inhibit transcription directly, or it can cause a conformational change that makes the genes unaccessible by closing

Question 30

How does methylation change chromatin structure

Answer 30

it can bind with methyl-binding proteins which will cause a closed conformational change

Question 31

if the fathers copy of a gene is expressed, is the sperm hyper or hypomethylated?

Answer 31

hypomethylated, his genes are active

Question 32

if the fathers copy of a gene is expressed, is the mothers egg hyper or hypo methylated?

Answer 32

hypermethylated, the mothers genes are inactive and silenced

Question 33

if the mothers copy of a gene is expressed, is the egg hyper or hypomehtylated

Answer 33

it is hypomethylated, the mothers genes are active

Question 34

true or false if a gene is imprinted during meiosis and there is a mutation where both genes from the parents provide a hypermethylated version of a gene, then it will likely be expressed in larger amounts than normal

Answer 34

false

Question 35

what are the two forms of post transcriptional regulation in eukaryotes

Answer 35

alternative splicing and RNA stability

Question 36

what regulates spliceosomes? how does this work?

Answer 36

splicing factors act to enhance or inhibit spliceosomes from recognizing splice sites

Question 37

what does a splicing repressor do

Answer 37

it causes an exon to be skipped

Question 38

what does a splicing enhancer do

Answer 38

it promotes the recognition of junctions and allows them to be spliced

Question 39

how do polyA-binding proteins aid in regulation

Answer 39

they promote RNA stability and increase its halflife

Question 40

what is the role of destabilzing elements on RNA stability

Answer 40

it destabilizes mRNA and makes it have a shorter half-life

Question 41

what are microRNAs

Answer 41

they are small segments of RNA in eukaryotes that bind to complementary mRNA and will be degraded by enzymes

Question 42

are microRNAs translated into proteins?

Answer 42

no lol

Question 43

what is the affect of microRNA

Answer 43

it causes the binding of double-stranded RNA which is then degraded by enzymes

Question 44

how is translation regulated in eukaryotes

Answer 44

by modulation of translation initiation factors that prevent the ribosome from binding

Question 45

how does phosphorylation impact translational initiation factors

Answer 45

it can inhibit or enhance translation

Question 46

what are some scenarios where translational regulation in eukaryotes is important

Answer 46

viral infection and starving

Question 47

what is proteolytic processing

Answer 47

post translational modification where an inactive protein is cleaved into an active form

Question 48

what are the irreversible and reversible post translational modifications for prokaryotes and eukaryotes

Answer 48

irrev: - proteolytic processing - attachment of prosthetic groups rev: - phosphorylation, acetylation, methylation

Question 49

what is the role of reversible modifications like phosphorylation in post-translational regulation

Answer 49

it allows us to turn polypeptides on or off

Question 50

what are somatic cells

Answer 50

they are body cells that undergo mitosis only

Question 51

what are germ cells

Answer 51

sperm and egg cells for reproduction

Question 52

what type of cell division do only germ cells undergo?

Answer 52

meiosis

Question 53

what are homologs

Answer 53

chromosomes of the same type

Question 54

how many chromosomes are in a homologous pair

Answer 54

2

Question 55

are chromosomes in a homologous pair 100% identical

Answer 55

no, they are not because they have different alleles

Question 56

why do homologous chromosomes have variation?

Answer 56

mutations produce alleles

Question 57

how are eukaryotic chromosomes inherited

Answer 57

they are inherited in pairs

Question 58

at S phase, how does the DNA content change?

Answer 58

it doubles

Question 59

what happens to the homologous pairs in S phase

Answer 59

they are each duplicated to form two sister chromatids

Question 60

how are sister chromatids related to eachother

Answer 60

they are 100% identical

Question 61

at the end of S phase, how many chromatids are there relative to the number of chromosomes

Answer 61

there are twice as many chromatids as there are chromosomes

Question 62

How can antisense RNA inhibit translation?

Answer 62

An antisense RNA binds to a transcript and inhibits translation.

Question 63

Which of the following is a mechanism to imprint genes?

Answer 63

methylation of cytosine