DNA Lesson 2 DNA Replication

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Lesson 2 

DNA Replication

2. DNA Replication

Learning Goals

You can explain why DNA replication takes place

You can describe how DNA replication takes place 

You can explain how data obtained by DNA analysis can ascertain the degree of kinship between species

Key words

DNA replication                                              

Helicase

DNA polymerase

RNA primase

Leading strand

Lagging strand

Replication bubble

Single Strand Binding protein

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0:00 - 04:80 Structure and function of DNA

04:80 - 12:59 DNA Replication (This lesson)

05:18

What is the opposite strand of:
5' AGGTCCG '3 ?

1. 5' TCCAGGC '3
2. 3' TCCAGGC '5
3. '3 AGGTCCG '5

06:09

Name the three differences between DNA and RNA

Which feature of our genetic material is not universal for all living creatures?

1. the linkage of phosphate and desoxyribose
2. The presence of 4 nitrogen bases: A, C, T en G
3. The presence of two complementary strands
4. The nucleotide sequence

DNA Replication = copying DNA so cell division can occur (= part of mitosis)

Mitosis or cell division starts with the synthesis of extra cell material (G1) , followed by doubling of its chromosomes (S phase) = replication, then more growth (G2) and verifying if the new cell parts (=chromosomes) are evenly distributed and lastly dividing the material over 2 cells (M = mitosis)

DNA Replication by DNA polymerase 

(p. 50)

= Synthesis direction

DNA replication = the doubling of the DNA during the S-phase of the cell cycle

Synthesis of a new nucelotide chain is assimilation

This costs energy or …..? Produced in....?

It is a chemical reaction

Enzymes are involved: which enzyme opens the double helix? Which enzyme attaches the nucleotides to the existing DNA strand? Where does the replication start?

How do you know, based on its name, that helicase is an enzyme? What kind of substance is an enzyme? Where will it be synthetised?  Enzymes are sensitive to...?

Energy or ATP

Energy is produced in mitochondria

Opens helix: Helicase

Attaching new nucleotides: DNA polymerase

Start: RNA primase

Name ends with -ase = enzyme

Enzyme = protein

Synthetised in ribosome

Sensitivity to pH and temperature because of their 3D structure

Refreshing: structure of DNA

A new nucleotide always attaches on C3 (phosphate in between).               -->

C3 -->

1.

2.

3.

4.

Step 1 DNA replication

Before replication of one cell is possible all nuclear DNA needs to be copied: 46 chromosomes --> 92 chromosomes.

Step 1. Splicing of the double helix by helicase

Which cells cannot replicate?

1. Nerve cells
2. Muscle cells
3. Epithelial cells
4. Red blood cells

Red blood cells have no nucleus, their origin starts in stem cells

Step 2 DNA Replication

DNA polymerase attaches to a RNA primer and starts adding nucleotides to form a new double strand

DNA replication: attaching to C3 atoms 

(remember slide 8)

Reading -->.                                                                   <-- Building

Okazaki fragment 

(next slide)

Single Strand Binding protein

Single Strand Binding proteins prevent the newly divided single strand DNA in the replication bubble to re-attach again to the other single strand 

            Order the 6 steps of replication 

1

2

3

4

5

6

Primase synthetises short RNA primers that function as starting point for DNA polymerase

RNA primers are replaced by DNA nucleotides

replication start at a replication startingpoint

Single Strand Binding proteins prevent DNA from becoming double stranded again

Helicase breaks hydrogen bonds en makes dsDNA ssDNA

DNA polymerase binds to a primer en lengthens this on the '3 end

www.bioplek.org

Primase

RNA Primer

SSBP's

DNA-polymerase

Helicase

Replication bubble: 

Leading and lagging strand

Result of S phase:

2 identical copies to distribute evenly over two nuclei

DNA helicase

1. synthesizes Hydrogen bonds
2. helps DNA polymerase to bind to DNA
3. unzips the DNA molecule
4. catalyses Hydrogen bonds

DNA polymerase

1. unzips the DNA
2. forms the new sugar phosphate backbone
3. joins A's and T's and G's and C's
4. proofreads the DNA to prevent mistakes

0

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50-52

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Learning Goals

You can explain why DNA replication takes place

You can describe how  DNA replication takes place 

You can explain how data obtained by DNA analysis can ascertain the degree of kinship between species