1 / 39

Gene Action

Gene Action. How does your cell makes very important proteins?. The production (synthesis) of proteins . 3 phases : 1. Transcription 2. mRNA processing 3. Translation. Nuclear membrane. DNA. Transcription. Pre-mRNA. RNA Processing. mRNA. Ribosome. Translation. Protein.

ketan
Download Presentation

Gene Action

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Gene Action

  2. How does your cell makes very important proteins? • The production (synthesis) of proteins. • 3 phases: 1. Transcription 2. mRNA processing 3. Translation

  3. Nuclear membrane DNA Transcription Pre-mRNA RNA Processing mRNA Ribosome Translation Protein DNA  RNA Protein Eukaryotic Cell

  4. 1. Transcription • mRNA molecules are produced by copying DNA by anenzyme called RNA polymerase. • Three bases in DNA code (codon)for one amino acid.

  5. DNA RNA Polymerase pre-mRNA 1. Transcription

  6. 2. mRNA Processing (Post transcription modification) Non coding region called introns are removed from the mRNA. The remaining portions of DNA that are translated into protein are called exons.

  7. 2. RNA Processing • Introns are pulled out and exonscome together. • End product is a mature RNA molecule that leaves the nucleus to the cytoplasm. • Introns bad…… Exons good!

  8. start codon A U G G G C U C C A U C G G C G C A U A A mRNA codon 1 codon 2 codon 3 codon 4 codon 5 codon 6 codon 7 A. matureMessengerRNA (mRNA) stop codon

  9. Types of RNA • Three types ofRNA: A. messenger RNA (mRNA) B. transfer RNA (tRNA) C. ribosome RNA (rRNA) • Remember: all produced in thenucleus!

  10. mRNA • Carries instructions from DNA to the ribosome.

  11. rRNA • Ribosome( Ribosomesare complex, bead-like structures composed of about 40% protein and 60% ribosomal RNA.) tRNA Contains anti condons to match the codons on mRNA. Gets the right amino acids to make the right protein according to mRNA instructions.

  12. amino acid attachment site amino acid U A C anticodon B. Transfer RNA (tRNA) A tRNA molecule transports an amino acid to the ribosome.

  13. 3. Translation • Three parts: 1. initiation: start codon (AUG) 2. elongation: 3. termination: stop codon (UAG,UAA,UGA)

  14. mRNA A U G C U A C U U C G Large subunit P Site A Site Small subunit

  15. aa2 aa1 2-tRNA 1-tRNA G A U U A C 3. TranslationInitiation 3. Translation anticodon A U G C U A C U U C G A hydrogen bonds codon mRNA

  16. aa3 3-tRNA G A A Elongation peptide bond aa1 aa2 1-tRNA 2-tRNA anticodon U A C G A U A U G C U A C U U C G A hydrogen bonds codon mRNA

  17. aa3 3-tRNA G A A aa1 peptide bond aa2 1-tRNA U A C (leaves) 2-tRNA G A U A U G C U A C U U C G A mRNA Ribosomes move over one codon

  18. aa4 4-tRNA G C U peptide bonds aa1 aa2 aa3 2-tRNA G A U (leaves) 3-tRNA G A A A U G C U A C U U C G A A C U mRNA Ribosomes move over one codon

  19. aa5 5-tRNA U G A peptide bonds aa1 aa2 aa3 aa4 3-tRNA G A A 4-tRNA G C U G C U A C U U C G A A C U mRNA Ribosomes move over one codon

  20. aa5 aa4 Termination aa199 aa200 aa3 primary structure of a protein aa2 aa1 terminator or stop codon 200-tRNA A C U C A U G U U U A G mRNA

  21. aa5 aa4 aa3 aa2 aa199 aa1 aa200 End Product • The end products of protein synthesis is a primary structure of a protein. • A sequence of amino acid bonded together by peptide bonds.

  22. Question: • The anticodon UAC belongs to a tRNA that recognizes and binds to a particular amino acid. • What would be the DNA base code for this amino acid?

  23. Answer: • tRNA - UAC (anticodon) • mRNA - AUG (codon) • DNA - TAC

  24. One Gene can code for more than one protein • The human genome has about 20,000 genes but our proteome (the total number of different proteins) is much larger (~100,000) • How can this occur? • Many genes can produce more than one protein .

  25. Alternative Splicing The process by which different mRNA are poduced from one gene by juggling exons. Exon 1 Exon 1 Exon 2 Exon 3 Exon 2 Exon 3 Exon 3 Exon 1 Exon 2 Exon 3 Exon 1 RESULT When each mRNA is translated, a different protein is produced

  26. Types of Genes • Structural Genes • These genes express structural and/or functional proteins such as enzymes • Regulatory Genes • These genes are short nucleotide sequences that express proteins that control the activity of structural genes .

  27. Gene Regulation • Gene regulation is turning a particular gene on or off.

  28. Gene Regulation in Eukaryotes Gene expression is regulated in a number of ways • The frequency of transcription of a gene can be controlled • Different mRNAs may be translated at different rates • Life span of a protein can be regulated

  29. Switching off genes • RNA technologies: RNAi and antisense RNA • RNAi and antisense RNA are biological mechanisms used for artificially manipulating gene expression. Tool used small interfering RNA(siRNA) Antisense RNA

  30. RNAi-Mechanism • -double stranded RNA introduced in the cell • Enzyme dicer cuts dsRNA into siRNA • siRNA combines with a cellular protein to form RISC (RNA induced silencing complex) • RISC unwinds the dsRNA • RISC oes to target mRNA and cuts it This stops the production of the protein

  31. Antisense RNA-Mechanism • Antisense RNA: Antisense RNA is a RNA strand which has a mirror image of nucleotide is introduced into a cell, it produces a RNA duplex  with the mRNA. The formation of double stranded RNA inhibits protein production.

  32. Applications Cancer gene therapy: RNAi and antisense RNA technologies have been used in reducing expression of cancer causing genes in  human cancer cell lines. Control of fruit ripening: Antisense RNA technology has been used to suppress expression of fruit ripening genes to make the fruits stay longer in vine and extend marketing period.

  33. Gene Regulation in Prokaryotes Prokaryotic DNA is organized into units called operons • Each operon consists of • A regulatory gene , which controls the transcription of other genes • A promoter , which RNA polymerase recognizes as the place to start transcribing • An operator , which governs access of RNA polymerase to the promoter • The structural genes , which encode for related proteins

  34. Gene Regulation in Prokaryotes • Bacteria have groups of genes that are controlled together and are turned on/off as required • One example, the lacoperon is a set of genes in bacteria used for lactose metabolism • Some bacteria use the disaccharide lactose as an energy source • Bacteria produce the enzymes to break down glucose and galactose only when lactose is present Gal Permease lactose B-Galactosidase Trans acetylase

  35. The Lac Operon RNA polymerase Operon • Three enzymatic proteins with specific functional roles in the metabolism of lactose Lac 1 P O Lac Z Lac Z Lac Z Promoter & Operator B-galactosidase Tans acetylase Lactose permease Repressor protein expressed by Lac regulatory regulatory gene

  36. When Lactose is absent RNA polymerase • No Transcription Lac 1 P O Lac Z Lac Z Lac Z Repressor Proteins

  37. When lactose is present Lac 1 P O Lac Z Lac Z Lac Z Lac Z Lac Z Lac Z mRNA inducer

  38. Identifying Active Genes • A DNA microarray (also commonly known as gene chip, DNA chip, or biochip) is used to measure the expression levels of genes.

  39. Micro array

More Related