protein synthesis n.
Skip this Video
Loading SlideShow in 5 Seconds..
Protein Synthesis PowerPoint Presentation
Download Presentation
Protein Synthesis

Loading in 2 Seconds...

play fullscreen
1 / 25

Protein Synthesis - PowerPoint PPT Presentation

  • Uploaded on

Protein Synthesis. 3 major processes: Replication → DNA copied to form 2 new DNA molecules Nucleus Transcription → DNA info copied to RNA Nucleus Translation → building a protein according to RNA instructions Cytoplasm. DNA Replication. DNA Replication.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Protein Synthesis' - holden

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
protein synthesis
Protein Synthesis
  • 3 major processes:
    • Replication→ DNA copied to form 2 new DNA molecules
      • Nucleus
    • Transcription → DNAinfo copied to RNA
      • Nucleus
    • Translation → buildinga protein according toRNA instructions
      • Cytoplasm
dna replication1
DNA Replication
  • DNA Replication = DNA  DNA
    • Parent DNA makes 2 exact copies of DNA
    • Occurs in nucleus
    • Why??
      • Occurs in Cell Cycle before MITOSIS so each new cell can have its own FULL copy of DNA

Models of DNA Replication

Segments of single-stranded DNA are called template strands.

Copied strand is called the complement strand (think “c” for copy)



  • DNA helicase (think “helix”)
    • binds to the DNA at the replication fork (origin of replication)
    • DNA strand separates into TWO
    • untwist (“unzips”) DNA using energy from ATP by breaking hydrogen bonds between base pairs at several places along the segments of DNA  called “origins of replication”
  • Single-stranded DNA-binding proteins (SSBP)
    • stabilize the single-stranded template DNA during the process so they don’t bond back together.
dna polymerase
DNA Polymerase
  • DNA Polymerase- adds nucleotides to the DNA strandsmakes POLYNUCLEOTIDES (1st function)

Helicase unzips the DNA molecule

DNA Polymerase adds nucleotides to create two NEW identical daughter molecules (A to T) and (G to C)

Complementary bases match up
    • Two new strands are formed
    • A with T
    • C with G

Antiparallel nature:

  • Sugar (3’end)/phosphate (5’ end) backbone runs in opposite directions
    • one strand runs 5’  3’,
    • other runs 3’  5’
  • DNA polymerase only adds nucleotides at the free 3’ end of NEW STRANDforming new DNA strands in the

5’  3’ direction only!!!

dna replication elongation
DNA Replication (Elongation)

After SSBP’s bind to each template…

  • Primase
    • primase is required for DNA synthesis
    • Like a “key” for a car ignition
    • makes a short RNA primers
      • Short pieces of RNA needed for DNA synthesis
  • DNA polymerase
    • adds nucleotides to RNA primer  makes POLYNUCLEOTIDES (1st function)
    • After all nucleotides are added to compliment strand…
      • RNA primeris removed and replaced with DNA by DNApolymerase (2nd function)
  • DNA ligase
    • “seals” the gaps in DNA
    • Connects DNA pieces by making phosphodiester bonds
elongation con t
Elongation (con’t)
  • Leading (daughter) strand
    • NEW strand made toward the replication fork (only in 5’ 3’ direction from the 3’ 5’ template strand
    • NeedsONERNA primer made by Primase
    • This new leading strand is made CONTINOUSLY
elongation con t1
Elongation (con’t)

Lagging (daughter) strand

  • NEW strand synthesis away from replication fork
    • Creates Okazaki fragments
      • Short pieces of DNA
    • Okazaki fragments joined by DNA ligase
      • “Stitches” fragments together
    • NeedsMANY RNA primer made by Primase

Supercoiled DNA relaxed by gyrase & unwound by

helicase + proteins:




SSB Proteins


DNA Polymerase




Lagging strand




base pairs


DNA Polymerase

RNA primer replaced by

DNA Polymerase & gap is

sealed by DNA ligase

5’  3’

RNA Primer

Leading strand


why replication again
Why Replication again?

DNA replication is necessary to create identical copies of DNA so it can be passed onto a new cell (cell division & reproduction)

accuracy of replication
Accuracy of Replication
  • Very low mistake rate (1/billion!) because cells have enzymes (like DNA Polymerase) that proofread, recognize,

and fix mistakes!

  • HOWEVER, mistakes

can happen 

MUTATIONS (cancer)

mistakes made during dna replication
Mistakes Made during DNA Replication
  • Mutation
    • Change in DNA (genetic material)
      • Frameshift(s)
        • extra or missing base(s).
      • Substitutions
        • when the wrong nucleotide is incorporated (mismatch mutation).
      • Deletions
        • Nucleotides are deleted shortening the DNA

Review: What is DNA replication?

A new sugar-phosphate backbone is made for each new strand

Base pairs are added

Two strands are created in place of the original strand