Preview

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Genes and DNA
Chapter 6
Preview
Section 1 What Does DNA Look Like? Section 2
How DNA Works
Concept Mapping
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Section 1 What Does DNA Look Like?
Chapter 6
Bellringer

• Can you explain the difference between traits and
  characteristics? Which is more closely associated
  with DNA and genes? Do you know where DNA and
  genes are found in the body? In specific cells?
• Write your answers in your science journal.

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Section 1 What Does DNA Look Like?
Chapter 6
Objectives

• List three important events that led to
  understanding the structure of DNA.
• Describe the basic structure of a DNA molecule.
• Explain how DNA molecules can be copied.

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Section 1 What Does DNA Look Like?
Chapter 6
The Pieces of the Puzzle

• DNA stands for deoxyribonucleic acid. DNA is the
  genetic material that determines inherited
  characteristics.

• Nucleotides The Subunits of DNA DNA is made of
  subunits called nucleotides. A nucleotide
  consists of a sugar, a phosphate, and a base.

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Section 1 What Does DNA Look Like?
Chapter 6
The Pieces of the Puzzle, continued

• Chargaffs Rule Erwin Chargaff found that the
  amount of adenine in DNA always equals the amount
  of thymine, and the amount of guanine always
  equals the amount of cytosine.
• Franklins Discovery Chemist Rosalind Franklin
  was able to make images of DNA molecules by using
  X-ray diffraction.

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Section 1 What Does DNA Look Like?
Chapter 6
The Pieces of the Puzzle, continued

• Watson and Cricks Model James Watson and
  Francis Crick used Chargaffs and Franklins
  research to build a model of DNA.
• The model, which looked like a long, twisted
  ladder, eventually helped explain how DNA is
  copied and how it functions in the cell.

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Section 1 What Does DNA Look Like?
Chapter 6
DNAs Double Structure

• The Double Helix The shape of DNA is known as a
  double helix.
• The two sides of the ladder are made of
  alternating sugar parts and phosphate parts.
• The rungs of the ladder are made of a pair of
  bases.

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Section 1 What Does DNA Look Like?
Chapter 6
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Section 1 What Does DNA Look Like?
Chapter 6
Making Copies of DNA

• How Copies Are Made During replication, a DNA
  molecule is split down the middle, where the
  bases meet. The bases on each side of the
  molecule are used as a pattern for a new strand.
• When Copies Are Made DNA is copied every time a
  cell divides. Each new cell gets a complete copy
  of all the DNA.

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Section 1 What Does DNA Look Like?
Chapter 6
Making Copies of DNA, continued
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Section 1 What Does DNA Look Like?
Chapter 6
DNA Replication
Click below to watch the Visual Concept.
Visual Concept
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Section 2 How DNA Works
Chapter 6
Bellringer

• Unscramble the following words
• tpsoneir
• neesg
• Now think of three words you associate with each
  of the above words and use them all in a
  paragraph that highlights what you know about
  DNA.
• Write your paragraph in your science journal.

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Section 2 How DNA Works
Chapter 6
Objectives

• Explain the relationship between DNA, genes, and
  proteins.
• Outline the basic steps in making a protein.
• Describe three types of mutations, and provide
  an example of a gene mutation.
• Describe two examples of uses of genetic
  knowledge.

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Section 2 How DNA Works
Chapter 6
Unraveling DNA

• DNA is often wound around proteins, coiled into
  strands, and then bundled up even more. In a cell
  that has a nucleus, the strands of DNA and
  proteins are bundled into chromosomes.
• A gene consists of a string of nucleotides that
  give the cell information about how to make a
  specific trait.

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Section 2 How DNA Works
Chapter 6
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Section 2 How DNA Works
Chapter 6
Genes and Proteins

• Proteins and Traits Proteins act as chemical
  triggers for many of the processes within cells.
  Proteins help determine traits.
• Help from RNA Another type of molecule that
  helps make proteins is called RNA, or ribonucleic
  acid. RNA is so similar to DNA that RNA can serve
  as a temporary copy of a DNA sequence.

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Section 2 How DNA Works
Chapter 6
Genes and Proteins, continued

• The Making of a Protein The first step in
  making a protein is to copy one side of the
  segment of DNA containing a gene. This copy is
  called messenger RNA (mRNA).
• A ribosome is a cell organelle composed of RNA
  and protein. A ribosome uses mRNA, transfer RNA
  (tRNA), and amino acids to make proteins.
• You can see the steps of protein production on
  the following two slides.

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Section 2 How DNA Works
Chapter 6
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Section 2 How DNA Works
Chapter 6
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Section 2 How DNA Works
Chapter 6
Changes in Genes

• Mutations Changes in the number, type, or order
  of bases on a piece of DNA are known as mutations.

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Section 2 How DNA Works
Chapter 6
Changes in Genes, continued

• Do Mutations Matter? There are three possible
  consequences to changes in DNA an improved
  trait, no change, or a harmful trait.
• How Do Mutations Happen? Mutations happen
  regularly because of random errors when DNA is
  copied. Any physical or chemical agent that can
  cause a mutation in DNA is called a mutagen.

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Section 2 How DNA Works
Chapter 6
Carcinogens and Mutagens
Click below to watch the Visual Concept.
Visual Concept
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Section 2 How DNA Works
Chapter 6
An Example of Substitution

• A mutation, such as a substitution, can be
  harmful because it may cause a gene to produce
  the wrong protein.
• A simple change in an amino acid can cause a
  disease such as sickle cell anemia, as shown on
  the next slide.

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Section 2 How DNA Works
Chapter 6
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Section 2 How DNA Works
Chapter 6
Uses of Genetic Knowledge

• Genetic Engineering Scientists can manipulate
  individual genes within organisms. This kind of
  manipulation is called genetic engineering.
• Genetic Identification Your DNA is unique, so
  it can be used like a fingerprint to identify
  you. DNA fingerprinting identifies the unique
  patterns in an individuals DNA.

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Genes and DNA
Chapter 6
Concept Mapping
Use the terms below to complete the Concept
Mapping on the next slide.
mutation amino acid nucleotide DNA adenine genes guanine proteins chromosomes cytosine

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Chapter 6
Genes and DNA
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Chapter 6
Genes and DNA