Ch. 10 Objectives

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Ch. 10 Objectives

• Today, you will be able to
• Describe the three parts of a nucleotide
• Relate the role of base pairing rules to the
  structure of DNA
• Summarize and explain the process of DNA
  replication
• Identify the role of enzymes in the replication
  of DNA

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• By the end of this unit I will be able to
• Outline the flow of genetic information in cells
  from DNA to protein
• Compare the structure of DNA with that of RNA
• Summarize the processes of transcription and
  translation
• Determine a protein sequence based on the genetic
  code

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Chapter 10

• DNA, Genes, and
• Proteins Synthesis

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What is a nucleic acid?

• A complex organic (carbon) macromolecule
• DNA Deoxyribonucleic Acid
• RNA Ribonucleic Acid

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What are the two main functions of DNA?

• To store information and to direct activities of
  the cell.
• -tells which proteins to make
• To copy itself exactly for new cells that are
  created

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What are DNA molecules made of?

• Two strands of repeating nucleotides
• A DNA nucleotide has three parts
• Deoxyribose a sugar
• Phosphate PO4
• Nitrogen Base
• (4 types A,T, C, G)

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The 4 DNA nucloetides

• Based on the 4 Nitrogenous bases
• A Adenine
• T Thymine
• C Cytosine
• G Guanine
• Adenine and Guanine have two rings of carbon and
  are called Purines
• Thymine and Cytosine have one ring of carbon and
  are called Pyrimidines

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Who discovered the structure of DNA?

• In 1953 Francis Crick and James Watson
• They proposed a model of DNA in which two
  nucleotide chains wrap around each other to form
  a double spiral- similar to a spiral staircase
• They called it a Double Helix

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Who discovered the structure of DNA?

• They relied heavily on scientific evidence
  reported by other scientists to construct their
  model. Evidence like the X-ray diffraction photo
  of DNA studied by Rosaline Franklin and Maurice
  Wilkins
• Crick, Watson, Wilkins received the Nobel Prize
  in Medicine in 1962

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The Structure of DNA

• A twisted ladder (double helix) helical

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What are the nitrogen base pairing rules?

• What do you notice about how the nitrogenous
  bases bond?

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What are the nitrogen base pairing rules?

• Adenine always bonds with Thymine
• Cytosine always bonds with Guanine

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What assumptions can you make about the
quantities or amount of each base that might be
found in a strand of DNA?
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What assumptions can you make about the
quantities or amount of each base that might be
found in a strand of DNA?

• If 15 of a particular sample of DNA was composed
  of Adenine, what is the composition of remainder
  of the DNA sample in regard to nucleotide bases?

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What assumptions can you make about the
quantities or amount of each base that might be
found in a strand of DNA?

• If 15 of a particular sample of DNA was composed
  of Adenine, what is the composition of remainder
  of the DNA sample in regard to nucleotide bases?
  Explain your reasoning for your answer.
• 15 A 15 T A T 30
• So 60 is composed of C and G
• 30 C and 30 G

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What is DNA replication and what happens during
it?

• The process of copying DNA in a cell is called
  replication.

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What is DNA replication and what happens during
it?

1. The two chains of DNA separate at the replication
   fork by enzymes called Helicases. They break the
   hydrogen bonds between the complementary base
   pairs.

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What is DNA replication and what happens during
it?

• Enzymes called DNA Polymerases move down each
  half strands and binds the new nucleotides to the
  existing DNA chains.
• DNA Polymerase synthesizes DNA in the
• 5 ? 3 direction

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What is DNA replication and what happens during
it?

• When replication is completed, two new exact
  copies of the original DNA molecule are produced
  and the cell is ready to divide.

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DNA replication is said to be semi-conservative.
What does this mean?
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Semi-conservative DNA Replication Each new
strand contains one side that is the original
parental DNA
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Identifying the sequence of a newly synthesized
DNA strand.

• You will be given one side of the DNA
• 5 CTA GCC TAC GGC 3
• 3 GAT CGG ATG CCG 5
• Reminder Which nucleotide pairs with which
• C,G
• A, T

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Your turn to solve for the newly created DNA
strand

• The sequence of bases on one strand of a DNA
  molecule is
• 5 GCC TAC GAA TTA CGT 3
• What would be the sequence of bases on the
  complementary strand?
• (Remember A-T and C-G)

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Your turn to solve for the newly created DNA
strand

• The sequence of bases on one strand of a DNA
  molecule is
• 5 GCC TAC GAA TTA CGT 3
• CGG.
• What would be the sequence of bases on the
  complementary strand?
• (Remember A-T and C-G)

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Journal

• DNA Replication Story Board