7.2

Question 1

Where is the promoter located

Answer 1

at the 5’ end adjacent to the coding region

Question 2

What are the three stages of transcription

Answer 2

initiation, elongation and termination

Question 3

what happens during initiation

Answer 3

initiation starts when RNA polymerase binds to the DNA at the promoter region and the double helix unwinds

Question 4

what happens during elongation

Answer 4

when mRNA becomes longer as nucleotides are added to the 3’OH group

Question 5

what happens during termination

Answer 5

the mRNA synthesis is complete and the complex of DNA, RNA polymerase and mRNA disassembles

Question 6

what happens when RNA polymerase has attached to the promoter

Answer 6

DAN separates at one end while it synthesizes a complementary RNA copy from the antisense DNA strand

Question 7

what is the DNA template strand

Answer 7

the antisense strand

Question 8

what lines up to the antisense strand

Answer 8

ribonucleoside triphosphate line up opposite to their exposed counterpart according to complementary base paring rules

Question 9

what happens after ribonucloside triphosphates have lines up to their exposed counterparts

Answer 9

RNA polymerase forms covalent bonds between the growing mRNA molecule and the ribonucleotides.

Question 10

where does the energy needed to drive the reaction come from

Answer 10

when the bond with the two additional phosphate groups are broken

Question 11

when does transcription end

Answer 11

when the RNA polymerase reaches a termination region of DNA, it just stops and then detaches from the DNA

Question 12

what is the DNA strand that is not transcribed called

Answer 12

the sense strand

Question 13

how is the mRNA different in prokaryotes to eukaryotes

Answer 13

there s no nucleus so it begins transcription immediately

however, in eukaryotes, the mRNA needs to be prepared for translation. this process is called post transcriptional modification of mRNA

Question 14

what is post transcriptional modification of mRNA

Answer 14

when it is prepared for translation after transcription

Question 15

why does post-transcriptional modification take place

Answer 15

because of the introns and exons in the eukaryotic genes. Introns are DNA sequences in eukaryotic genes that contain no coding information. Sometimes, they contain controlling sequences that regulate the transcription of the gene. Exons are the DNA sequences that code for a polypeptide

Question 16

brief steps of modifying RNA for translation

Answer 16

transcription (synthesis of pre mRNA), addition of a 5’ cap and a poly A tail (which protects the mRNA molecule from degradation) and finally splicing, which involves removing (excising) the introns and joining (ligating) the exons to form mature mRNA

Question 17

what is a spliceosome

Answer 17

a large ribunucleoprotein (RNP) complex made up of five small nuclear ribonucleoproteins (snRNPS) and several proteins. It acts as an enzyme in the splicing process to remove introns and bind exons together.

Question 18

what does the splicing of introns involve

Answer 18

spliceosome

Question 19

steps of how spliceosome removes introns and joins exons to form mature mRNA

Answer 19

1. snRNP forms base pairs with the ends of introns

spliceosome and looped intron form

intron is excised

exons are ligated, spliceosome disassembles

mature mRNA

Question 20

what does splicing allow for

Answer 20

several proteins to be synthesized from the same gene

Question 21

what genes have more exons

Answer 21

tropomyosin has 11 exons

Question 22

how many forms of the protein scan b made from genes due to alternative splicing

Answer 22

at least five forms of protein

Question 23

where does post transcriptional regulation not take place

Answer 23

in prokaryotes

Question 24

Gene expression might be altered at the level of post-transcriptional processing in eukaryotes and not in prokaryotes because?

Answer 24

eukaryotic exons may be spliced in alternative patters

Question 25

What is removed from pre-RNA to form mature eukaryotic mRNA?

Answer 25

introns

Question 26

What is removed from pre-RNA to form mature eukaryotic mRNA?

Answer 26

introns

Question 27

what direction does transcription occur

Answer 27

5 prime to 3 pime

Question 28

what does the promoter do

Answer 28

it directly affects transcription by controlling whether or not RNA polymerase can access the gene

Question 29

what is an operon

Answer 29

an operon is a set of genes all linked to a single promoter.

Question 30

what is an operator

Answer 30

a sequence of DNA in prokaryotes that allows a cell to regulate whether a gene is transcribed or not. this stops the binding of RNA polymerase with the promoter

Question 31

what is a lac operon

Answer 31

a group of genes/ operon with a single promoter

Question 32

regulatory proteins

Answer 32

these can increase the rate of transcription or decrease it positive transcription factor or negative transcription factor

Question 33

where are operon usually found

Answer 33

usually in prokaryotes but can occur in eukaryotic

Question 34

RNA polymerase

Answer 34

starts transcription, needs a promoter

Question 35

what does RNA polymerase need to start transcription

Answer 35

a promoter

Question 36

what is an operator

Answer 36

a part of the DNA, a repressor can bind to it

Question 37

what happens if a repressor binds to the operator

Answer 37

it stops RNA polymerase from moving forward and making mRNA.

Question 38

name an example of regulating transcription

Answer 38

a lac operon three genes involved with lac operon, enzymes bacteria want lactose lacI codes for the repressor lacI is also bound to a promoter

Question 39

what happens if lactose is not present with the lac operon

Answer 39

if lactose is not present, the repressor binds to the operator, blocking mRNA polymerase, proteins cannot be created

Question 40

what happens if lactose is present with the lac operon

Answer 40

if lactose is present, it binds to the repressor, changing the conformation of the repressor and can no longer bind to the operator, polymerase can then carry on and make mRNA. the mRNA then can make enzymes to break down the lactose sugar and the cycle continues

Question 41

what does transcriptional regulation ensure

Answer 41

that certain genes are transcribed and other remain silent meaning that they are not transcibred

Question 42

what do activator proteins bind to

Answer 42

enhancers

Question 43

what do repressor proteins bind to

Answer 43

silencers

Question 44

what are enhancers and silencers examples of

Answer 44

non-coding regions of DNA with specific functions

Question 45

In response to the presence of certain food sources, prokaryotes can do which of the following?

Answer 45

alter the level of transcription of certain genes

Question 46

transcription regulation

Answer 46

allows the cell to produce proteins only needed at the time is highly efficient at completely preventing transcription can be controlled by repressor proteins

Question 47

what is not a DNA sequence to which proteins can bind in order to regulate gene expression

Answer 47

a repressor

Question 48

what are two additional ways of regulating transcription

Answer 48

involve small chemical changes to both histones and DNA histones can be acetylated or methylated

Question 49

what chemical change can take place to DNA

Answer 49

it can be methylated

Question 50

what chemical changes can take place on histones

Answer 50

can be acetylated and methylated

Question 51

why do histones influence transcription

Answer 51

when they bind to DNA they Blick access to RNA polymerase

Question 52

what happens when histone proteins are activated

Answer 52

an acetyl group is added to the tails of histones proteins which prevents the bindings between nucleosomes. This partially unwinds the DNA allowing for enzymes involved in transcription to access it. As s result activation of histones generally keeps the genes active while deacetylation, removal of the acetyl group silences the gene

Question 53

what affect does acetylation of histones have

Answer 53

keeps the genes active

Question 54

what affect does deacetylation have on histones

Answer 54

silences the gene

Question 55

what happens when a histone is methylated

Answer 55

a methyl group is added, it can have a positive or negative effect on transaction depending on where the histones are located on the genome

Question 56

What is DNA methylation

Answer 56

when a methyl group is added to a cytosine found within a DNA molecule

Question 57

what plays a ole as a methyl donor

Answer 57

SAM

Question 58

what DNA base is methylated

Answer 58

cytosine

Question 59

what does cytosine become when it methylated

Answer 59

methylcytosine

Question 60

what generally happens when DNA is methylated

Answer 60

the DNA is usually not expressed as the nucleotides are shut down

Question 61

how long does mythelaticn last for

Answer 61

a long time

Question 62

what does methylation cause

Answer 62

the inactivation of the second X chromosomes in females for the duration of the life oft aha cell

Question 63

what is the level f DNA methylation of the genome associated with

Answer 63

diet, environmental conditions, age

Question 64

what is the study of epigenetic

Answer 64

the study of heritable changes in organisms that are brought abotu by changes in gene expression rather than by modification of the genetic code

Question 65

what happens if epigenetic change

Answer 65

the DNA sequence itself is not altered but some of the bases are altered

Question 66

epigenesis in mice; influence of a methylated food source on coat color

Answer 66

mice coats can be dark or yellow depending on the methylation of the gene for this trait. when methylated, the coat color is brown, when not methylated, the gene I active and the coat is yellow exposing mice during pregnancy t a diet high in folic acid (contains methyl) increased the proportion of dark mice in their litters. indirect evidence that increased methylation of genes in the fetus can influence the inheritance of a trait

Question 67

what happens to methylation during DNA replication

Answer 67

it does not change

Question 68

what is produced during transcription

Answer 68

all types of RNA

Question 69

where does transcription take place in eukaryotes

Answer 69

in the cell nucleus

Question 70

What is the name of the non-coding section of DNA to which the RNA polymerase binds to initiate transcription

Answer 70

promoter