Q2-FUN11/Transcription and regulation of gene expression

Question 1

At what steps of transcription does regulation occur at?

Answer 1

1. chromatin structure
2. transciption initiation
3. mRNA stability
4. transcript processing

Question 2

What are the 3 major functions of RNA within the cell?

Answer 2

copying genetic info from DNA, helps make ribosomes, help build new polypeptides

Question 3

The structure of DNA is _____ while the structure of RNA is _________

Answer 3

Question 4

DNA is located in the _______ while RNA is located in the _________

Answer 4

Question 5

What types of RNAs are involved in transcription and translation?

Answer 5

mRNA, rRNA, tRNA

Question 6

What are snRNAs?

Answer 6

small nuclear RNAs, they function in a lot of nuclear processes, inc. splicing pre-mRNA

Question 7

What are ncRNAs?

Answer 7

they are non-coding RNAs. They function is a lot of different cellular processes, including

-regulation of gene expression.

• X-chromosome inactivation
• protein transport.

Question 8

What distinct signals are encoded within the DNA sequence of a gene?

Answer 8

start and stop

Question 9

Where does transcription start and end at?

Answer 9

it starts at the transcription start site (TSS, located at the end of the promoter region) and ends at the terminator site.

Question 10

Each gene has a _________ promoter

Answer 10

unique

Question 11

What are the two types of promoters?

Answer 11

basal promoter element and enhancer element

Question 12

What is an enhancer?

Answer 12

Enhancers are regulatory DNA sequences that, when bound by proteins called transcription factors, enhance the transcription of a gene.

Question 13

What is a basal promoter?

Answer 13

it is bound by RNA poly II and basal transcription factors

Question 14

What is an example of a basal promoter?

Answer 14

TATA box - most common

2-30 base pairs from transcriptional site

can bind basal TFs and RNA poly II

Question 15

What typically catalyses transcription?

Answer 15

RNA poly II

Question 16

How does RNA poly II work?

Answer 16

it transcribes one of the 2 DNA strands of the gene. it reads its template from 3’ to 5’ and makes an RNA copy of 5’ to 3’.

It incorportates AGCU when making the mRNA copy of the DNA

Question 17

What are the 3 stages of transcription?

Answer 17

initiation, elongation, termination

Question 18

What happens in initiation of transcription?

Answer 18

RNA poly II binds to DNA and unwinds a 17-18 bp segment of the promoter. This segment is called the open complex.

Question 19

Explain what happens during elongation of transcription.

Answer 19

RNA Pol II moves along the template until it reaches the terminator region. During this phase, an area of DNA under the RNA pol II stays unwounded. This unwounded part is called the transcription bubble and it moved along the DNA.

Question 20

What 2 things happen during temination?

Answer 20

1. transcription continues beyond the protein coding region (3’ UTR)
2. endonuclease (enzyme that cleaves mRNA) cleaves abt 20 base pairs beyond the sequence

Question 21

What is the primary transcript?

Question 22

What are hnRNAs?

Answer 22

heterogenous nuclear RNA. bulk of transcribed RNAs that hasnt been processed

(processed means hasnt been 5’ capped and no poly A tail)

Question 23

What are the 2 types of post translational mRNA processing?

Answer 23

5’ capping and 3’ poly A tail

Question 24

explain 5’ capping.

Answer 24

add a 7-methyl-guanosine residue to the 5’ end of the mRNA.

the mRNA is catalysed by guanylyltransferase (capping enzyme) and then methylated by a methyltransferase enzyme

the 1st and 2nd nucleotides are also methylated

Question 25

Why is 5' capping important?

Answer 25

it protects the mRNA from degraded by exonucleases, promotes nuclear export, helps with the recognition of translational machinery

Question 26

explain the 3' poly A tail addition to the primary transcript.

Answer 26

after the polyadenylation signal sequence has been recognized (and endonuclease has been recruited and mRNA has been cleaved), Poly(A) polymerase adds abt 40-250 adenines to the cleaved 3' end

Question 27

What determines the stability of mRNA?

Answer 27

3' UTR (untranslated region) sequence determines the stability of mRNA

Question 28

What is the poly A tail on an mRNA transcript stabilized by?

Answer 28

poly-A binding protein (PABP), binds approx 30 residues

Question 29

What happens to the poly A tail over its lifetime?

Answer 29

it gets gradually shortened

Question 30

What happens when the PABP can no longer bind?

Answer 30

the 30 base pairs get degraded

Question 31

Which part of the mRNA transcript gets spliced out?

Answer 31

introns get spliced out

Question 32

what carries out the splicing of introns in an mRNA transcript?

Answer 32

spliceosome

Question 33

what is a spliceosome made out of?

Answer 33

large comple of RNA and proteins, small nuclear RNAs + proteins = small nuclear ribonuceloproteins (snRNPs)

Question 34

what do snRNP's do?

Answer 34

the facilitate splicing by located specific seqences at the end of each intron, cutting them out, and rejoining the exons together

Question 35

explain how snRNP's work.

Answer 35

Question 36

Explain differential splicing/exon shuffling.

Answer 36

it is a way for a single primary transcript to be spliced into different mRNAs, by the inclusion of diff sets of exons https://www.youtube.com/watch?v=JEylX4cQvpg

Question 37

What are the 2 types of genes?

Answer 37

constitutive genes and inducible genes

Question 38

Are constitutive genes essential?

Answer 38

yes they are essential and nessessary for life

Question 39

Are constitutive genes constantly expressed or only on some of the time?

Answer 39

since they are nessessary for life, they are continuously expressed

Question 40

What are inducible genes?

Answer 40

inducible genes are genes that only need to be turned on some of the time when they are required

Question 41

What do inducible genes determine?

Answer 41

development and tissue specificity

Question 42

What do inducible genes allow cells to do?

Answer 42

they allow cells to respond to the environment

Question 43

Inducible gene expression is controlled by _________________ proteins

Answer 43

transcription factor

Question 44

what is an example of Inducible gene expression is controlled by transcription factor proteins?

Answer 44

steroid hormones bind to steroid receptor transcription factors. these form a homodimer that finds and binds to certain DNA sequences

Question 45

transcription factors are proteins that bind to a specific ________ in the gene promoter

Answer 45

DNA sequence

Question 46

Transcription factors control the rate of \_\_\_\_\_\_

Answer 46

transcription

Question 47

What on the transcription factor determines the rate of transcription?

Answer 47

binding sites

Question 48

What do miRNAs do?

Answer 48

they are small strands of RNA (20-25 nucleotides) that regulate gene expression

Question 49

miRNAs are transcribed from \_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 49

DNA

Question 50

do miRNAs make proteins?

Answer 50

no they are non-coding RNA

Question 51

the primary function of miRNA is to ________ gene expression

Answer 51

down regulate

Question 52

what are the 2 ways miRNA blocks gene expression?

Answer 52

it promotes RNA degradation by binding to complementary sequences in 3' UTR and induces degradation it binds to mRNA and blocks translation