DNA- Replication

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DNA- Replication

• Chapter 9, Section 2 3Regular Biology

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Objectives

• Describe structure of DNA
• Explain importance of DNA
• Understand why living things need to make copies
  of DNA
• Describe how copies of DNA are made
• Explain what happens if a mutation occurs in
  replication

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Structure of DNA
Deoxyribose Nucleic Acid

• Double helix
• Made of 2 strands of nucleotides
• Phosphate
• Sugar (deoxyribose)
• Nitrogen Base
• Adenine (A)
• Thymine (T)
• Cytosine (C)
• Guanine (G)

Nucleotide
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About DNA

• Sugar Phosphate make up the sides
• In the middle of DNA
• Adenine pairs with Thymine (A-T)
• Cytosine pairs with Guanine (C-G)
• Practice

• TATGGAGAGTC

• ATACCTCTCAG

Complementary base pairs
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More Practice

• 1. GTATTCAGGA

CATAAGTCCT
2. TAACAGA
ATTGTCT
3. GATTACA
CTAATGT
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Names to Know, pg 196

• Chargaff- (1949) A pairs with T. G pairs with
  C
• Mrs. Franklin- (1952) X-ray pictures of DNA
• Watson Crick- (1953) DNA is double helix

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Prokaryote DNA is

• Prokaryote DNA is circular
• Has 2 replication forks
• Replication occurs in opposite directions around
  the circle until they meet
• Can replicate in 1 hour or less

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Eukaryote DNA is

• Eukaryote DNA is double stranded
• Compacted in chromosomes
• Each chromosome can have about 100 replication
  forks
• Each new DNA strand is about 100,000
  nucleotides long.
• The DNA in your body would wrap around the Earth
  about 1.5 times!
• Takes about 8 hours to replicate human
  chromosomes in Interphase

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Prokaryote vs Eukaryote
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Make a Venn Diagram
Prokaryote vs Eukaryote DNA
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Replication-
Making more DNA

• Happens in the nucleus

• Occurs during Interphase
• S (synthesis) phase
• Occurs whenever is needed

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Replication- Making more DNA

• Important for Mitosis and Meiosis
• Mitosis- new cells for growth repair
• Meiosis- new cells for sperm egg
• Important for making more copies of a protein,
  enzyme, etc

Why?
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Replication- making more DNA

• Two strands separate, forming replication fork
• DNA polymerase (an enzyme) brings bases to make
  new strands
• 500/sec in bacteria, 50/sec in humans.WOW!
• Half of DNA strand is old and half is new
• Result two strands of DNA form that are
  identical to the original molecule

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But what if theres a mistake?

• Types of Mutations
• Frameshift- (the new part of DNA shifts to be
  longer or shorter than it should be)
• Deletion
• Correct base is deleted
• Insertion
• Incorrect Base is added
• Point mutation (base pair substitution)
• Wrong base pair is stuck in the place of another

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Build-in Mutation Reducers

• Replication has proof-readers to help reduce
  errors
• DNA polymerase
• Chaperone proteins
• These proteins and enzymes reduce errors to about
  1 error for every 1 billion nucleotides.

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But what if a mutation DOES happen?

• DNA RNA Protein

(Genes)
(Enzyme)
Discussion!
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Genetic Technology- Terms to Know

• Genetic engineering-
• Recombinant DNA- DNA made from 2 or more
  organisms
• Vector- What gets the gene into the cell
• Usually a virus, yeast, or plasmid
• Plasmid- circular bits of DNA
• Restriction enzymes- proteins which cut the DNA
  at specific points

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New Technology

• Human Genome Project- mapping entire human genome
  sequence. Finished in 2003.
• Cloning- process used to creating identical copy
  of organism
• Polymerase Chain Reaction (PCR)- process that
  makes more DNA
• DNA Fingerprinting- use gel electrophoresis to
  separate DNA of different lengths

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Genetic Engineering Information

• Gel Electrophoresis
• Uses electric charges within gel
• DNA is negative, thus travels to positive end
• Separates molecules by size

http//learn.genetics.utah.edu/units/biotech/
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More New Technology

• Genetically Modified Foods- genetically selecting
  certain traits for crop improvement
• Transgenic Animals- Animals that have other DNA
  in their cell. Used to make proteins, medicine,
  etc.
• Gene Therapy- insert genes into organism to help
  stop or prevent disease

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Remember
There is no gene for Human Spirit!