Gene expression
This presentation is the property of its rightful owner.
Sponsored Links
1 / 24

Gene Expression PowerPoint PPT Presentation


  • 51 Views
  • Uploaded on
  • Presentation posted in: General

Gene Expression. Early evidence indicating most genes specify the structure of proteins Garrod’s work on inborn errors of metabolism in early 1900s Beadle and Tatum’s work with Neurospora mutants in the 1940s. An “inborn error of metabolism”. Mutations affecting biochemical pathways.

Download Presentation

Gene Expression

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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Gene Expression


  • Early evidence indicating most genes specify the structure of proteins

    • Garrod’s work on inborn errors of metabolism in early 1900s

    • Beadle and Tatum’s work with Neurospora mutants in the 1940s


An“inborn errorof metabolism”


Mutationsaffectingbiochemical

pathways


  • Information flow from DNA to protein

    • Transcription

      • RNA molecule complementary to the template DNA strand synthesized

    • Translation

      • Polypeptide chain specified by messenger RNA (mRNA) is synthesized


Nucleotidestructure of

RNA


Overview of transcription and translation


  • Structure of RNA

    • RNA

      • Formed from nucleotide subunits

      • Each nucleotide subunit contains ribose, a base, and three phosphates

      • Like DNA, RNA subunits are covalently joined by a 5΄—3΄ linkage to form alternating sugar-phosphate backbone


  • Transcription

    • Incoming nucleotides with three phosphates pair with complementary bases on the DNA strand

    • RNA polymerase cleaves two phosphates from each nucleotide and covalently links the remaining phosphate to the 3΄end of the RNA chain


Transcription


Synthesis of mRNA


  • Translation

    • Polypeptide chain specified by the mRNA is synthesized

      • Initiation

      • Repeating cycles of elongation

      • Termination

    • Each sequence of three nucleotide bases in the mRNA constitutes a codon

    • Requires tRNAs and cell machinery, including ribosomes


Three representations of a tRNA molecule


Ribosomestructure


Initiation of translation in bacteria


Elongation cycle in translation


Termination of translation


  • Coupled transcription and translation in bacteria

    • Unlike eukaryotic cells, in bacterial cells translation and transcription coupled

    • Translation of the bacterial mRNA molecule usually begins before the 3´ end of the transcript is completed


Coupled transcription and transla-tion in bacteria


  • Retroviruses

    • Flow of genetic information is reversed by reverse transcriptase

      • Enzyme associated with retroviruses

      • Retroviruses synthesize DNA from an RNA template

      • Example of retrovirus is HIV-1, AIDS virus


Infection cycle of an RNA tumor virus


  • Mutations

    • Base substitution mutations

      • Often result from errors in base pairing during replication

      • Missense mutations

      • Nonsense mutations

    • Frameshift mutations

      • One or two nucleotide pairs are inserted into or deleted from the molecule


  • Some mutations involve larger DNA segments

    • Due to change in chromosome structure

    • Wide range of effects as they involve many genes

      • DNA sequences that “jump” into the middle of a gene

      • Known as transposons or transposable genetic elements

      • Most are retrotransposons


Mutations


  • Login