Unit B5 & 6: Cell Biology Unit B5 & 6: Cell Biology (DNA Replication(DNA Replication) ) Authored by Michelle ChomaAuthored by Michelle Choma©©

Students who have fully met the prescribed learning Students who have fully met the prescribed learning outcomes (PLO’s) are able to:outcomes (PLO’s) are able to:

B5. Describe DNA replication.B5. Describe DNA replication. Describe the three steps in the semi-conservative Describe the three steps in the semi-conservative

replication of DNA:replication of DNA: ““unzipping” (DNA helicunzipping” (DNA helicasease)) complementary base pairing (DNA polymercomplementary base pairing (DNA polymerasease)) joining of adjacent nucleotides (DNA polymerjoining of adjacent nucleotides (DNA polymerasease))

This is it!! Short one Eh!?This is it!! Short one Eh!?

Describe the purpose of DNA replication.Describe the purpose of DNA replication.

Identify the site of DNA replication within the cell.Identify the site of DNA replication within the cell.

B6. DescribeB6. Describe recombinant DNA.recombinant DNA. Define recombinant DNA.Define recombinant DNA.

Describe a minimum of three uses for Describe a minimum of three uses for recombinant DNA.recombinant DNA.

IntroductionIntroduction

Recall the structural composition and Recall the structural composition and functions of DNA. See B4 functions of DNA. See B4

DNA ReplicationDNA Replication

PurposePurpose::

Before a cell divides, it needs to Before a cell divides, it needs to double the number of chromosomes double the number of chromosomes (containing genes/traits, (containing genes/traits, codons/protein codes) codons/protein codes) i.e. the DNA is duplicated for each new i.e. the DNA is duplicated for each new

daughter cell.daughter cell.

LocationLocation::

Nucleus, mitochondrion (and plant Nucleus, mitochondrion (and plant chloroplasts); requires 2 enzymes chloroplasts); requires 2 enzymes helichelicasease and DNA and DNA polymerpolymerasease..

Helicase

DNA Polymerase

ProductsProducts::

2 DNA molecules; 1 identical to 2 DNA molecules; 1 identical to original.original.

This is known as This is known as semiconservative semiconservative replicationreplication, which produces two , which produces two “half-old and half-new” DNA strands.“half-old and half-new” DNA strands.

3 basic steps:3 basic steps:

1.) Unzipping1.) Unzipping 2 strands of DNA 2 strands of DNA

unwind AND unzip unwind AND unzip the H-bonds the H-bonds between N-base between N-base pairs using pairs using helichelicasease..

Next stepNext step

2.) Complementary base pairing2.) Complementary base pairing New nucleotides present in the New nucleotides present in the

nucleus (T, C, A, G) bond with the nucleus (T, C, A, G) bond with the complementary pairs on the parental complementary pairs on the parental strandstrand i.e.i.e. A-T, G-C, T-A, A-T, G-C, T-A, and and C-G C-G using using DNA DNA

polymerpolymerasease

And lastly….And lastly….

3.) Joining of adjacent nucleotides3.) Joining of adjacent nucleotides Adjacent nucleotides join/form a Adjacent nucleotides join/form a

bond with the help of bond with the help of DNA DNA polymerpolymerasease (“proof-reader”) to form (“proof-reader”) to form new sugar-phosphate backbones new sugar-phosphate backbones resulting in 2 identical DNA resulting in 2 identical DNA molecules. This is referred to as molecules. This is referred to as semi-conservativesemi-conservative..

Recombinant DNA (rDNA)Recombinant DNA (rDNA)

Definition:Definition: DNA/genome from two different organisms DNA/genome from two different organisms

are spliced together to obtain a desired are spliced together to obtain a desired trait/characteristic or perform a specific trait/characteristic or perform a specific function; the manipulation of a genome function; the manipulation of a genome from two or more sources, such as from two or more sources, such as bacteria, plants or animals.bacteria, plants or animals. E.g. Bacteria nucleic acid containing a human E.g. Bacteria nucleic acid containing a human

hormone gene and producing biotechnology hormone gene and producing biotechnology products, i.e. insulin, growth hormone.products, i.e. insulin, growth hormone.

Uses:….there are lots!Uses:….there are lots!

Production of hormones (insulin, growth Production of hormones (insulin, growth hormone), human proteins (interferon, hormone), human proteins (interferon, antibodies) and vaccines from bacteria.antibodies) and vaccines from bacteria.

Development of pest-resistant, frost-Development of pest-resistant, frost-resistant, disease-resistant, altered oil resistant, disease-resistant, altered oil content and ripening etc. in crops. Plants content and ripening etc. in crops. Plants can also be engineered to produce human can also be engineered to produce human hormones, proteins, and antibodies.hormones, proteins, and antibodies.

Production of DNA probes for Production of DNA probes for paternity/maternity, body ID at crime paternity/maternity, body ID at crime scenes, evolutionary relationships etc.scenes, evolutionary relationships etc.

Some moreSome more Transgenic animals, or genectically altered Transgenic animals, or genectically altered

organisms (GMO’s) to increase productivity, organisms (GMO’s) to increase productivity, produce pharmaceuticals, produce organs, produce pharmaceuticals, produce organs, research in cancer/tumour cells etc.research in cancer/tumour cells etc.

Transgenic bacteria used for vaccines, biofilter Transgenic bacteria used for vaccines, biofilter airborne pollutants, synthesize hormones, airborne pollutants, synthesize hormones, enzymes for making cheese, clean oil spills, enzymes for making cheese, clean oil spills, extract precious metals in mining.extract precious metals in mining.

In medicine for the diagnosis and treatment of In medicine for the diagnosis and treatment of genetically inherited disorders, e.g. cystic fibrosisgenetically inherited disorders, e.g. cystic fibrosis

To give an organism a metabolic capability it did To give an organism a metabolic capability it did not possess before.not possess before.

To create more copies of a specific gene so it can To create more copies of a specific gene so it can be studied.be studied.

What do this fish and

This ice cream have in This ice cream have in common?common?

mmmmm……smooth ice mmmmm……smooth ice creamcream

““Anti-freeze” gene from arctic pout Anti-freeze” gene from arctic pout are inserted into a yeast which then are inserted into a yeast which then generates the anti-freeze proteingenerates the anti-freeze protein

This protein is added to ice cream to This protein is added to ice cream to make it smoother (smaller ice make it smoother (smaller ice crystals)crystals)

Hmmmm…. Is this a good idea? What Hmmmm…. Is this a good idea? What do you think?do you think?