as 90715 describe the role of dna in relation to gene expression l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
AS 90715 Describe the role of DNA in relation to gene expression PowerPoint Presentation
Download Presentation
AS 90715 Describe the role of DNA in relation to gene expression

Loading in 2 Seconds...

play fullscreen
1 / 21

AS 90715 Describe the role of DNA in relation to gene expression - PowerPoint PPT Presentation


  • 193 Views
  • Uploaded on

Part two…. AS 90715 Describe the role of DNA in relation to gene expression. The Replication of DNA. Take me to NZQA Documents relating to this standard. Contents. Why replicate? (revision stuff you probably already know) The basics The enzymes Okazaki fragments Fixing errors

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

PowerPoint Slideshow about 'AS 90715 Describe the role of DNA in relation to gene expression' - maurice


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
as 90715 describe the role of dna in relation to gene expression

Part two…

AS 90715Describe the role of DNA in relation to gene expression

The Replication of DNA

Take me to NZQA Documents relating to this standard

contents
Contents
  • Why replicate? (revision stuff you probably already know)
  • The basics
  • The enzymes
  • Okazaki fragments
  • Fixing errors
  • Review Questions
why replicate
Why replicate?

Stuff that any respectful Bio student really should know…

Mitosis and Meiosis

What are they and where they happen!

Meiosis Revision exercise

  • DNA replicates before it forms a chromatid. I.e. when it still looks like…
  • Over an organisms life the DNA in the zygote is copied trillions of times with minimal error. Error rates are generally 1 in 50 million base pairs (bp).

When we copy this 100,000,000,000,000 times it turns into this

why replicate4
Why replicate?

www.cellsalive.com

  • Each new cell must have a copy of the entire DNA genome.

Some of the DNA released from a single human chromosome

dna replication the very basics
DNA Replication - the very basics

The basics of DNA REPLICATION

  • Unwind – Unzip – Add nucleotides – wind it all back up.
  • If only it could be that simple
  • Two things make it a little more fiddly
    • DNA is a VERY LONG double helix chemical molecule
    • It has a anti-parallel structure
anti parallel structure of dna

It’s a long Double Helix

Anti-parallel structure of DNA
  • The molecule of DNA in a single human chromosome ranges in size from 50,000,000 bp (1.7 cm) up to 250,000,000 (8.5 cm).

Ever tried unraveling a long bit of string?

  • Check the DNA length calculator
dna replication forks
DNA replication forks
  • Because the DNA chromosome is soooooooooo long it needs multiple replication forks working at the same time. How this is coordinated and how strands are placed back together is beyond the scope of L3 Bio (so don’t worry bout it)
dna replication
DNA Replication

The detail.

  • 4 different enzymes (see next slide)
  • DNA polymerase moves along template strand in 3’ to 5’ direction.
  • McGraw Animation
  • You tube - Replication song.
anti parallel structure dna
Anti-parallel structure (DNA)
  • This diagram shows a lot of stuff not yet discussed.
  • What you need to understand at this point
  • When an enzyme (DNA polymerase) travels along a strand of DNA it travels in the 3’ to 5’ direction of the original strand

DNA Polymerase travels 3’ to 5’ on original strand

okazaki fragments
Okazaki Fragments

An Okazaki fragment is a relatively short fragment of DNA created on the lagging strand. The lengths of Okazaki fragments are between 1,000 to 2,000 nucleotides long in E. coli and are generally between 100 to 200 nucleotides long in eukaryotes.

Each Okazaki fragment is joined together by DNA ligase after the primers have been removed.

http://www.youtube.com/ Replication animation

http://www.youtube.com/ crash course in DNA (summary)

semi conservative replication
Semi-conservative replication

A simple idea really…

  • S.C.R is simply the formation of two double helix molecules where each molecule contains one of the original strands and one new strand of nucleotides (daughter strand).
  • This helps to minimise the errors made in replication as each molecule contains a copy of the original nucleotide sequence.
checking for errors
Checking for errors

You don’t need to know the detail in this box. But read it cause it is interesting ;-)

  • In general, DNA polymerases are extremely accurate, making less than one error for every 107 nucleotides added. Even so, some DNA polymerases also have proofreading ability; they can remove nucleotides from the end of a strand in order to correct mismatched bases.
review questions
Review Questions

http://www.biologycorner.com DNA Quizs

review question
Review Question

2011 NCEA exam – Q1 (b)

  • When DNA is replicated, each of the parent strands acts as a template.
  • Explain why there is a difference in the way in which the parallel strands of DNA are replicated.
  • You may use a labelled diagram to support your answer.
review question17
Review Question
  • What words are hidden under the yellow boxes?

Click to show answer

Click to show answer

Click to show answer

Click to show answer

review question18
Review Question
  • Complete the table
review question19
Review Question
  • Add the 3’ and 5’ labels to the diagram

Click for answers