Transcription, the central dogma and splicing

Question 1

what will be produced from transcription

Answer 1

RNA strand that is complimentary to one strand of DNA

Question 2

transcription process

Answer 2

-rna is synthesised from a DNA template by RNA polymerase. -RNA polymerase targets a site on the DNA–> moving from left to right opening it it up -5’ to 3’ -as the enzyme moves along it adds nucleotides to the growing RNA strand

Question 3

pyrophosphate

Answer 3

two phosphates e.g. lost during dna synthesis and transcription with nucleotides

Question 4

simple transcription process

Answer 4

1. RNA polymerase 2. DNA locally single stranded –> one strand is a template 3.NTPS (nucleotide triphosphate) 0ATP, CTP, GTP< TTP etc) 4. 2 phosphates are lost (pyrophosphate) 5. RNA synthesis 5’ to 3’ ALWAYs

Question 5

which direction

Answer 5

5’ to 3’ always

Question 6

transcriptome

Answer 6

set of all RNA molecules within a cell- including all mRNA- amount of RNA will depend on cell type

Question 7

genome

Answer 7

all dna within cell

Question 8

DNA vs RNA

Answer 8

-rna is unstable- so short term- more reactive due to extra hydroxyl group on 2 prime carbon -rna is only single stranded (no back up info) -rna is ore protein to mutations e.g. if cytosine losses amine group, it will change to URACIL–> would not be detected as a mutation since uracil is a base pair in RNA (however since U does not exist in DNA it would be detected by mismatch Mut protein -uracil instead of thymine -ribose although single stranded it can pair with itself, causing local regions of double helix

Question 9

RNA can form..

Answer 9

double stranded regions, therefore a form 3D complexes

Question 10

why is RNA more prone to mutations than DNA

Answer 10

if cytosine loses amine group, it will change to uracil this change would not be detected as a mutation since uracil is a base pair in RNA (however as it does not exist in DNA it would be detected

Question 11

uracil instead of

Answer 11

thymine in RNA

Question 12

ribose instead of

Answer 12

deoxyribose in RNA

Question 13

why does ran polymerase know when to stop transcription

Answer 13

due to stop and start codons

Question 14

what other proteins does RNA polymerase bind with when it binds to the promotor

Answer 14

transcription factors

Question 15

what is the basic promoter required for

Answer 15

to shows the enzyme where to start

Question 16

the structure and function of a cell depends on..

Answer 16

what proteins are produced and in what quantities

Question 17

differences in gene expression is due to

Answer 17

differences in both translation and transcription

Question 18

what happens when the polymerase reaches stop codon

Answer 18

it is released from the DNA

Question 19

how is the new RNA chain formed??

Answer 19

by losing a pyrophosphate to forma a sugar phosphate back bone

Question 20

RNA is more reactive due to..

Answer 20

an extra hydroxyl group on 2 carbon on the pentose

Question 21

RNA doesn’t bind without..

Answer 21

transcription factors

Question 22

there will be no transcription if there is no..

Answer 22

transcription factor

Question 23

the transcription factors ill attach to..

Answer 23

the control region, just before the promotor region–>causes RNA polymerase to attach

Question 24

what ion is found in the active site of polymerase

Answer 24

Mg2+

Question 25

during transcription there will be a ….. in the polymerase

Answer 25

a short region of DNA/RNA helix

Question 26

what is the central dogma

Answer 26

The central dogma of molecular biology describes the flow of genetic information in cells from DNA to messenger RNA (mRNA) to protein.

Question 27

main flow idea of the central dogma

Answer 27

-DNA- transcription- RNA–translation– protein

Question 28

transcription occurs in the

Answer 28

nucleus

Question 29

translation occurs in the

Answer 29

cytoplasm

Question 30

mRNA is processed before it leaves the nucleus and can be..

Answer 30

translated many times

Question 31

what does processing of preRNA involve

Answer 31

nucleotides are added to the 5’ and 3’ end -5’ end:nucleotide is added via 5’5’ linkage- capped by an A typical nucleotide -3’ end: tail of nucleotides added (AAAAA)–> poly A nucleotides SPLICING also must occur to remove introns

Question 32

what happens to the 5’ prime end of preRNA

Answer 32

nucleotide is added via 5’5’ linkage- capped by an A typical nucleotide

Question 33

what happens to the 3’ end of preRNA

Answer 33

tail of nucleotides added (AAAAA)–> poly A nucleotides

Question 34

splicing involves..

Answer 34

the removal of introns

Question 35

why is splicing important

Answer 35

eukaryotic genes are interrupted by non-coding sequences –> prevents faulty proteins from being produced

Question 36

which unit carries out splicing

Answer 36

spliceosome- catalyses the reaction too areas for ligation and cleavage are determined by the many sub-units of the spliceosome

Question 37

what marks a mature RNA- s that it is allowed to be exported out of the nucleus

Answer 37

RNA binding proteins

Question 38

afte rbeing translated many times over…

Answer 38

the cell degrades the mRNA

Question 39

what effects the mRNA half life..

Answer 39

the sequence of the mRNA

Question 40

in human transcripts how many genes exhibit alternative splicing

Answer 40

95%

Question 41

alternative splicing

Answer 41

regulated process during gene expression that results in a single gene coding for multiple proteins. In this process, particular exons of a gene may be included within or excluded from the final, processed messenger RNA (mRNA) produced from that gene.

Question 42

simple alternative splicing

Answer 42

where a single gene can code for many proteins due to the variability in splicing pattern e.g. exons of genes may be included or excluded production of multiple protein isoforms

Question 43

RNA hypothesis

Answer 43

some believed RNA came before DNA- W.Gilberts -According to the RNA World Hypothesis, life later evolved to use DNA and proteins due to RNA’s relative instability and poorer catalytic properties, and gradually, ribozymes became increasingly phased out.

Question 44

first stage of post transcriptional control

Answer 44

splicing-important regulatory step in determining which functional proteins are produced from gene expression. Thus, splicing is the first stage of post-transcriptional control.

Question 45

splicing process

Answer 45

on either Side of the RNA there is a 5’ splice site and a 3’ splice site - the nucleosome will first cleave the rna on the 5’ end , and the the ran will form a loop attaching t the 3’ ran intron. -3’ end is now cleaved and a circular intron is formed called an INTRON LARIAT -exons on either side will then be rejoined by a ligase