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Gene Regulation results in differential Gene Expression, leading to cell Specialization. Eukaryotic DNA. Epigenetics – Ghost in Your Genes. Watch to see how your environment and your choices influence inheritance… http://www.youtube.com/watch?v=CiAyLPeCTMU&feature=share&list=PLA2E1F3FFBFAE1CB6.

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gene regulation results in differential gene expression leading to cell specialization

Gene Regulation results in differential Gene Expression, leading to cell Specialization

Eukaryotic DNA

epigenetics ghost in your genes
Epigenetics – Ghost in Your Genes
  • Watch to see how your environment and your choices influence inheritance…
  • http://www.youtube.com/watch?v=CiAyLPeCTMU&feature=share&list=PLA2E1F3FFBFAE1CB6
differential gene expression
Differential Gene Expression
  • Nucleosome Packing: DNA wraps around histone proteins to form a structure called a nucleosome. Nucleosomes help pack DNA into eukaryotic chromosomes.
    • When acetyl groups attach to the histone proteins the DNA in chromosomes loosens to allow for transcription.
    • The addition of methyl groups to histone proteins can cause DNA to condense thus preventing transcription.
  • In Genomic Imprinting, methylation regulates expression of either the maternal or paternal alleles of certain genes at the start of development.
organization of typical eukaryotic genes

Fig. 18-8-3

Organization of Typical Eukaryotic Genes

Poly-A signal

sequence

Enhancer

(distal control elements)

Proximal

control elements

Termination

region

Exon

Intron

Exon

Intron

Exon

DNA

Upstream

Downstream

Promoter

Transcription

Exon

Intron

Exon

Intron

Exon

Primary RNA

transcript

Cleaved 3 end

of primary

transcript

5

RNA processing

Intron RNA

Poly-A

signal

Coding segment

mRNA

3

Start

codon

Stop

codon

Poly-A

tail

3 UTR

5 Cap

5 UTR

the roles of transcription factors
The Roles of Transcription Factors
  • Regulatory Proteins, repressors and activators, operate similarly to those in prokaryotes, influencing how readily RNA polymerase will attach to a promoter region. In many cases, numerous activators are acting in concert to influence transcription.
slide6

Fig. 18-9-3

Promoter

Activators

Gene

DNA

Distal control

element

Enhancer

TATA

box

General

transcription

factors

DNA-bending

protein

Group of

mediator proteins

RNA

polymerase II

RNA

polymerase II

Transcription

initiation complex

RNA synthesis

coordinately controlled eukaryotic genes
Coordinately controlled eukaryotic genes
  • A particular combination of control elements can activate transcription only when the appropriate activator proteins are present.
  • All cells of an organism have all chromosomes/genes but certain genes are only active in certain cells. The transcription factors present in the cell determine which genes will be active and which won’t (but they are both still present)
slide8

Fig. 18-10

Enhancer

Promoter

Albumin gene

Control

elements

Crystallin gene

LIVER CELL

NUCLEUS

LENS CELL

NUCLEUS

Available

activators

Available

activators

Albumin gene

not expressed

Albumin gene

expressed

Crystallin gene

not expressed

Crystallin gene

expressed

(a) Liver cell

(b) Lens cell

post transcriptional regulation
Post Transcriptional Regulation
  • Alternate Gene Splicing - different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns
slide10

Fig. 18-11

Exons

DNA

Troponin T gene

Primary

RNA

transcript

RNA splicing

or

mRNA

noncoding rnas role in gene expression
Noncoding RNAs role in gene expression
  • RNA Interference, noncoding RNAs play multiple roles in controlling gene expression. MicroRNAs (miRNAs) and Small inserting RNAs (siRNAs) are small single-stranded RNA molecules that can bind to mRNA. These can degrade mRNA or block its translation. The difference between the two is that they form from different RNA precursors.
slide12

Fig. 18-13

Hairpin

miRNA

Hydrogen

bond

Dicer

miRNA

miRNA-

protein

complex

5

3

(a) Primary miRNA transcript

mRNA degraded

Translation blocked

(b) Generation and function of miRNAs