Control Of Gene Expression: Eukaryotes Flashcards

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1
Q

Chromosomal protein alterations?

A

DNA → packed with history proteins into nuclessomes
DNA is inaccessible to RNA polymerase and transcription factors
Histones → have “tails” with t+ve charged AA attracted to negatively charged DNA

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2
Q

Define acetyl ‘ation

A

Allows transcription
To tails
Adds acetal group which changes charges & opens up the nucleosome to allow access to RNA polymerase
Positively charged histore tails

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3
Q

Define beacetylation?

A

Inhibits transcription
It gene is to be switched off
History deacetylase enzyme con remove acetal groups to inhibit access to RNA polymerase

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4
Q

Define Epigenetic’s ?

A

Study of heritable changes in gene expression that occur without changes in the DNA sequence
Histone acetylation → set early in embryo function

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5
Q

What is histone deacetylation determined by?

A

DNA methylation →
Methyl group is covalently added to 5’ carbon of cytosine forming 5 - methyl cytosine
Catalysed by DNA methyltransferase

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6
Q

When does methylation occur and where?

A

Usually occur in a C & G doublet called Cp G islands → often in promoter regions
Diagonally opposite cytosines on the 2 strands of double helix are methylated

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7
Q

Can methylation patterns be inherited?

A

Yes mitosis ‘

Usually inherited when DNA replicates prior tomitosis
Maintenance methylate catalyses formation of 5 - methyl cytosine in new strand.
Prior to mitosis → much of methylatan pattern removed by demethylases.
Some is still inherited → previous gen can affect future gen

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8
Q

What are affects of DNA methylation?

A

Methyl groups in promoter region attract history deaceylases → transcription repression
Methylated genes otter inacté

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9
Q

X-chromosome inactivation

A

Females → potential to prod x2 protein from genes on ne chromosome

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10
Q

Define regulator sequence?

A

Different genes need to be regulated so must have same in promoters
A single regulator proteins → regulate expression
E.g.) activate 3 genes A, b,c - combat stress drought
Brought stress activates transcription of single regulator protein gene
The regulator protein binds to regulator sequencein promoters of genes AB C to stimulate transcription
Genes → A, BIC prod diff proteins participating in the drought stress response in coordinated way

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11
Q

How dues transcriptional initiation work in pro &Euk ?

A

Pro→ RNA polymerases binds to directly recognitori sequence on promoter (pribnow box)
EUK → general transcription factors bind to recognition in sequence on promoter ( TATA box)
RNA polymerases binds to general transcription factors assembled on the chromosomes

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12
Q

Define specific transcription factors?

A

Bind to regulatory protein binding sequences/ regulatory elements just upstream.
Can either be activators / REPRessors.
STF → bind to protein complex called mediator which facilitates the interaction with the basal transcription apparatus

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13
Q

What are enhancers /silencers?

A

Enhancer sequence → bind to additional activators
Silencer sequence → bind to additional repressors ‘
Additional regulatory protein binding sequences are thousands of base pairs from the transcriptional start site
In order for such enhancers/silencers to interact with basal transcription apparatus → DNA bends bringing distant regulatory sequence into close proximity to promoter

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14
Q

Define introns?

A

Non-coding sequence within a gene which separates the protein coding “exon”
Introns are transcribed but removed before final mRNA leaves the nucleus
DNA → introns, exons
Pre-mrna → interns, exons
mRNA → exons

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15
Q

What is spliceosome?

A

An RNA splicing machine
Small nuclear ribonucleoprotein particles ( snrnps) cut pre-mrna release introns and splice exons together
Processing part 2_
* G - cap = added at 5’ end (G TP) protects it from being digested by ribonuclease and facilitate ribosomes binding
* poly A tail added at 3’ end assists in export from nucleus and stabilises the mRNA

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16
Q

Trans port control / mRNA stability control?

A
17
Q

What are Micro RNA’s?

A

Micro RNA’s (mi RNA) → post transcriptional regulators of gene expression

Coded by DNA
RNA transcripts have a sequence which allows them to fold back on themselves by base pairings to form double stranded hairpins
Recognized by dicer proteins
→ cut by DIC ER to form 22 short bp double strand ed fragments
1 strand → incorporated into RNA - induced silencing complex (RISC)
Guided to target mRNA by complementary base pairings
Causes target mRNA degradation & inhibits translation

18
Q

What is posttranslation aspects of protein synthesis?

A

Eukaryotic cells
→ polypeptide may be moved from synthesis site to an organelle or out of the cell
Often modified with more chemical bonds
AA sequence also contains signal sequence → “address label”

19
Q

What is destinations for newly translated polypeptides in EUK cells.

A

As polypeptide chai is made, information contained in its AA sequence may target the protein to a organelle
Father modifications en occur in ER or transfer to Golgi
PROTEOLYSIS: cutting of the polypeptide chain
GLYCOSYLATION: addi lion of sugars to the protein to form glycoproteins
PHOSPHORYLATION: additions of phosphate groups to proteus

20
Q

How are reporter genes made?

A

Step 1: isolate the promoter gene of plant cab
Step 2: choose a reporter
Step 3: isolate the coding sequence of E. Coil
Step 4, join promoter to Gus coding sequence to create recombinant reporter construct
Step 5: generically engineer a transgenic plant containing the reporter construct
Target plant contains → reporter construct as well as original gene
Whenever original transcribed so is report here
If we con detect Gus also las expert