Home > Documents > Chapter 13 Section 2: DNA Replication - Quia · PDF fileChapter 13 Section 2: DNA Replication...

Chapter 13 Section 2: DNA Replication - Quia · PDF fileChapter 13 Section 2: DNA Replication...

Date post: 11-Mar-2018
Category:
Author: vanthuy
View: 215 times
Download: 2 times
Share this document with a friend
Embed Size (px)
of 37 /37
Chapter 13 Section 2: DNA Replication
Transcript
  • Chapter 13 Section 2:

    DNA Replication

  • Opening Activity

    DNA is considered to be a relatively stable molecule.

    What gives it this stability, even though the hydrogen

    bonds between the nitrogen bases are easily broken?

    Write out your answer, then share and compare your

    ideas with other students.

  • Content Objectives

    I will be able to identify:

    How DNA replicates, or makes a copy of itself.

    What the roles of proteins are in DNA replication.

    How DNA replication is different in prokaryotes and eukaryotes.

  • Adapted from Holt Biology 2008

    Chapter 13 Section 2: DNA Replication

    Key Vocabulary Terms

  • DNA Replication

    The process of making a copy of DNA

  • DNA Helicase

    An enzyme that unwinds the DNA double helix during DNA replication

  • DNA Polymerase

    An enzyme that catalyzes the

    formation of the DNA molecule.

  • Replication Forks

    A replication fork is the mechanism by which a

    strand of DNA is synthesized. Unzip the DNA and it looks like a

    fork, ie fork in road, not eating fork.

  • Adapted from Holt Biology 2008

    Chapter 13 Section 2: DNA Replication

    Supplementary Words

  • Histones

    Remember:

    Long molecules of DNA are

    tightly wound around

    proteins called histones

  • Replication bubbles By starting replication at many sites along the chromosome. Two distinct replication forks

    form at each start site, and replication occurs in opposite directions. This process forms

    replication bubbles along the DNA molecule.

  • Adapted from Holt Biology 2008

    Chapter 13 Section 2:

    DNA Replication

    Notes

  • Your Turn Activity

  • DNA Replication

    Because DNA is made of two strands of complementary base pairs, if the strands are separated then each strand can serve as a pattern to make a new

    complementary strand.

  • DNA Replication

    The process of making a copy of

    DNA is called DNA replication.

  • DNA Replication

    In DNA replication, the DNA molecule

    unwinds, and the two sides split. Then, new

    bases are added to each side until two identical sequences

    result.

  • DNA Replication, continued

    As the double helix unwinds, the two complementary strands of DNA separate from each other and form Y shapes. These Y-shaped

    areas are called replication forks.

  • DNA Replication, continued

    At the replication fork, new nucleotides are added to each side and new base pairs are formed according to the base-pairing rules.

  • DNA Replication, continued

    Each double-stranded DNA helix is made of one new strand of DNA and one original strand of

    DNA.

  • Three steps in replication: 1. Unwinding and separating the DNA

    strands

    2. Adding complimentary bases

    3 Formation of two identical molecules

  • Replication Proteins

    The replication of DNA involves many proteins that form a machinelike complex of moving parts. Each protein has a specific

    function.

  • Replication Proteins

    Proteins called DNA helicases unwind the

    DNA double helix during DNA replication. These

    proteins wedge themselves between the

    two strands of the double helix and break the

    hydrogen bonds between the base pairs.

  • Replication Proteins

    Proteins called DNA polymerases catalyze the formation of the

    DNA molecule by moving along each strand and adding

    nucleotides that pair with each base.

  • Replication Proteins, continued

    DNA polymerases also have a proofreading

    function. During DNA replication, errors sometime occur

    and the wrong nucleotide is added to

    the new strand.

  • Replication Proteins, continued

    If a mismatch occurs, the DNA polymerase

    can backtrack, remove the incorrect

    nucleotide, and replace it with the

    correct one.

  • DNA Helicase

    unwinds the helix

    Function of enzymes (proteins) of

    replication

  • DNA polymerase: add new

    nucleotides to the open DNA strand

    proofread to prevent errors

    Function of enzymes (proteins) of

    replication

  • Review Questions

    1. What is the first step in DNA replication?

    Which enzyme performs this step?

    Unwinding and separating DNA

    strands

    DNA Helicase

  • Review Questions

    2. When in the cell cycle does DNA replication occur?

    Interphase (S)

  • Review Questions

    3. What would happen if DNA polymerase didnt correct errors?

    It would change the DNA code

    causing mutations or a change

    in the function of the cell.

  • Prokaryotic and Eukaryotic Replication

    Prokaryotic cells usually have a single chromosome

    which is a closed loop attached to the inner cell

    membrane.

    Replication in prokaryotes begins at one place along the loop. This site is called the origin of replication.

  • Eukaryotes and prokaryotes replicate their chromosomes differently.

    Eukaryotic cells often have several chromosomes which are linear and contain both DNA and

    protein.

    In eukaryotic cells, replication starts at many sites along the

    chromosome.

    This process allows eukaryotic cells to replicate their DNA faster

    than prokaryotes.

  • Prokaryotic and Eukaryotic Replication Click to animate

  • Prokaryotic and Eukaryotic Replication

    Two distinct replication forks form at each start

    site, and replication occurs in opposite directions.

    This process forms

    replication bubbles along the DNA molecule.

    Replication bubbles

    continue to get larger as more of the DNA is copied.

  • The smallest eukaryotic chromosomes are often 10 times the size of a prokaryotic chromosome.

    Eukaryotic chromosomes are so long that it would take 33 days to replicate a typical human

    chromosome if there were only one origin of replication.

    Some prokaryotes replicate their DNA and form two

    new cells in 20 minutes.

  • Prokaryotic and Eukaryotic Replication

    Human chromosomes are replicated in about

    100 sections that are 100,000 nucleotides long, each section with its own starting point.

    Because eukaryotic cells have multiple

    replication forks working at the same time, an entire human chromosome can be replicated in

    about 8 hours.

  • Summary

    In DNA replication, the DNA molecule unwinds, and the two sides split. Then, new bases are added to each side until two identical sequences result.

    The replication of DNA involves many proteins that form a machinelike complex of moving parts.

    In prokaryotic cells, replication starts at a single site. In eukaryotic cells, replication starts at many sites along the chromosome.


Recommended