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Copyright © by Holt, Rinehart and Winston. All rights reserved.
Module C: Chapter 4
Genes and DNA
Section 1: What Does DNA Look Like?
Section 2: How Does DNA Work?
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Does DNA Look Like?
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.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Does DNA Look Like?
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.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Does DNA Look Like?
The Pieces of the Puzzle
• Nucleotides: The Subunits of DNA DNA is made of
subunits called nucleotides that. A nucleotide consists of a
sugar, a phosphate, and a base.
• Chargaff’s Rule Erwin Chargaff found that the amount of
guanine always equals the amount of cytosine.
• Franklin’s Discovery Chemist Rosalind Franklin was
able to make images of DNA molecules.
• Watson and Crick’s Model James Watson and Francis
Crick used Chargaff’s and Franklin’s research to build a
model of DNA.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
What Does DNA Look Like?
DNA’s Double Structure
• The Double Helix The shape of DNA is shown on the
next slide. As you can see, a strand of DNA looks like a
twisted ladder.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 1
DNA Structure
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Section 1
What Does DNA Look Like?
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.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How DNA Works
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.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How DNA Works
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.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How DNA Works
Unraveling DNA
• Coiled and Bundled 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, as shown on the
next slide.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
Unraveling DNA
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How DNA Works
Genes and Proteins
• Proteins and Traits Proteins help determine how tall you
grow, what colors you can see, and whether your hair is
curly or straight.
• 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.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How DNA Works
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. You can see the next steps of protein production on
the following two slides.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
The Making of a Protein: A
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Section 2
The Making of a Protein: B
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Section 2
How DNA Works
Changes in Genes
• Mutations Changes in the number, type, or order of
bases on a piece of DNA are known as mutations.
• 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.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How DNA Works
An Example of Substitution
• Sickle Cell Anemia is a disease that affects red blood
cells. It is caused by a substitution that causes a change in
a single amino acid in a blood protein.
•The DNA sequence GAA, when copied as mRNA, gives
the instructions to place the amino acid glutamic acid into
the growing protein.
•If the original DNA sequence is changed to GTA, the
sequence will code for the amino acid valine instead.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How DNA Works
An Example of Substitution, continued
•When valine is substituted for glutamic acid in a blood
protein, the red blood cells are changed into a sickle shape.
•The genetic origin of sickle cell anemia is shown on the
next slide.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2
How Sickle Cell Anemia Results from a Mutation
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Section 2
How DNA Works
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 individual’s DNA.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 6
The Cell in Action
Concept Map
Use the following terms to complete the concept map on
the next slide: mutation, amino acids, nucleotide, DNA,
adenine, genes, guanine, proteins, chromosomes,
cytosine.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 6
Concept Map
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 6
Concept Map
Copyright © by Holt, Rinehart and Winston. All rights reserved.