Transcription, the central dogma and splicing Flashcards Preview

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Flashcards in Transcription, the central dogma and splicing Deck (45):
1

what will be produced from transcription

RNA strand that is complimentary to one strand of DNA

2

transcription process

-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

3

pyrophosphate

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

4

simple transcription process

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

5

which direction

5' to 3' always

6

transcriptome

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

7

genome

all dna within cell

8

DNA vs RNA

-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

9

RNA can form..

double stranded regions, therefore a form 3D complexes

10

why is RNA more prone to mutations than DNA

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

11

uracil instead of

thymine in RNA

12

ribose instead of

deoxyribose in RNA

13

why does ran polymerase know when to stop transcription

due to stop and start codons

14

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

transcription factors

15

what is the basic promoter required for

to shows the enzyme where to start

16

the structure and function of a cell depends on..

what proteins are produced and in what quantities

17

differences in gene expression is due to

differences in both translation and transcription

18

what happens when the polymerase reaches stop codon

it is released from the DNA

19

how is the new RNA chain formed??

by losing a pyrophosphate to forma a sugar phosphate back bone

20

RNA is more reactive due to..

an extra hydroxyl group on 2 carbon on the pentose

21

RNA doesn't bind without..

transcription factors

22

there will be no transcription if there is no..

transcription factor

23

the transcription factors ill attach to..

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

24

what ion is found in the active site of polymerase

Mg2+

25

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

a short region of DNA/RNA helix

26

what is the central dogma

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

27

main flow idea of the central dogma

-DNA- transcription- RNA--translation-- protein

28

transcription occurs in the

nucleus

29

translation occurs in the

cytoplasm

30

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

translated many times

31

what does processing of preRNA involve

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

32

what happens to the 5' prime end of preRNA

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

33

what happens to the 3' end of preRNA

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

34

splicing involves..

the removal of introns

35

why is splicing important

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

36

which unit carries out splicing

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

37

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

RNA binding proteins

38

afte rbeing translated many times over...

the cell degrades the mRNA

39

what effects the mRNA half life..

the sequence of the mRNA

40

in human transcripts how many genes exhibit alternative splicing

95%

41

alternative splicing

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.

42

simple alternative splicing

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

43

RNA hypothesis

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.

44

first stage of post transcriptional control

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

45

splicing process

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