DNA

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Unit 7 Lesson 1 DNA Structure and Function
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Unit 7 Lesson 1 DNA Structure and Function
Florida Benchmarks
• SC.7.N.1.1 Define a problem from the seventh
grade curriculum, use appropriate reference
materials to support scientific understanding, plan
and carry out scientific investigations of various
types, such as systematic observations or
experiments, identify variables, collect and
organize data, interpret data in charts, tables, and
graphics, analyze information, make predictions,
and defend conclusions.
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Unit 7 Lesson 1 DNA Structure and Function
Florida Benchmarks
• SC.7.N.1.5 Describe the methods used in the
pursuit of a scientific explanation as seen in
different fields of science such as biology, geology,
and physics.
• SC.7.L.16.1 Understand and explain that every
organism requires a set of instructions that
specifies its traits, that this hereditary information
(DNA) contains genes located in the chromosomes
of each cell, and that heredity is the passage of
these instructions from one generation to another.
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Unit 7 Lesson 1 DNA Structure and Function
Florida Benchmarks
• HE.6.C.1.4 Recognize how heredity can affect
personal health.
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Unit 7 Lesson 1 DNA Structure and Function
Cracking the Code
What is DNA?
• The genetic material in cells is contained in a
molecule called deoxyribonucleic acid, or DNA.
• Scientists describe DNA as containing a code. A
code is a set of rules and symbols used to carry
information.
• To understand how DNA functions, you first need
to learn about the structure of the DNA molecule.
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Unit 7 Lesson 1 DNA Structure and Function
How was DNA discovered?
• Many scientists from all over the world contributed
to our understanding of DNA.
• Some scientists discovered the chemicals that
make it up.
• Other scientists learned about how these
chemicals fit together.
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Unit 7 Lesson 1 DNA Structure and Function
Unraveling DNA
What does DNA look like?
• Experiments and imaging techniques have helped
scientists to infer the shape of DNA.
• The structure of DNA is called a double helix.
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Unit 7 Lesson 1 DNA Structure and Function
What does DNA look like?
• The two sides of the ladder shape are made of
sugars and phosphate groups.
• The rungs of a DNA strand are made of pairs of
bases.
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Unit 7 Lesson 1 DNA Structure and Function
What does DNA look like?
• The building block of DNA is called a nucleotide,
which is a base, a sugar, and a phosphate group.
• There are four different nucleotides in DNA.
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Unit 7 Lesson 1 DNA Structure and Function
What does DNA look like?
• The bases in nucleotides are paired, or
complementary.
• Adenine always pairs with thymine (A-T).
• Cytosine always pairs with guanine (C-G).
• The order of the nucleotides in DNA is a code that
carries information.
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Unit 7 Lesson 1 DNA Structure and Function
What does DNA look like?
• Genes are segments of DNA that relate to a
certain trait.
• The code in the nucleotide order has information
about which proteins the cells should build.
• The types of proteins that your body makes help
determine your traits.
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Unit 7 Lesson 1 DNA Structure and Function
Replication and Mutation
How are copies of DNA made?
• The cell makes copies of DNA molecules through a
process known as replication.
• During replication, the DNA separates.
• The bases on each side are used as a pattern for a
new strand.
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Unit 7 Lesson 1 DNA Structure and Function
How are copies of DNA made?
• As replication proceeds, complementary
nucleotides are added.
• When replication is complete, there are two
identical DNA molecules.
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Unit 7 Lesson 1 DNA Structure and Function
How are copies of DNA made?
• Describe what is happening in the diagram.
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Unit 7 Lesson 1 DNA Structure and Function
When are copies of DNA made?
• Before a cell divides, it copies its DNA.
• Our cells can replicate DNA in just a few hours,
because replication begins in many places along a
DNA strand.
• Many groups of proteins are working to replicate
your DNA at the same time.
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Unit 7 Lesson 1 DNA Structure and Function
What are mutations?
• Mutations are changes in the number, type, or
order of bases on a piece of DNA.
• There are three main kinds of mutations:
deletions, insertions, and substitutions.
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Unit 7 Lesson 1 DNA Structure and Function
What are mutations?
• In a deletion mutation, a base is left out.
• In an insertion mutation, an extra base is added.
• The most common mutation, substitution,
happens when one base replaces another.
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Unit 7 Lesson 1 DNA Structure and Function
What are mutations?
• Which type of mutation is shown in each row?
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Unit 7 Lesson 1 DNA Structure and Function
What are mutations?
• Mutations can happen by random error, and also
by damage to the DNA molecule by physical or
chemical agents called mutagens.
• Cells make proteins that can fix errors in DNA, but
sometimes the mistake is not corrected.
• The mistake then becomes part of the genetic
code.
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Unit 7 Lesson 1 DNA Structure and Function
What are mutations?
• A genetic disorder results from mutations that
harm the normal function of the cell.
• Some harmful mutations are inherited, or passed
on from parent to offspring. Others can lead to
cancer.
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Unit 7 Lesson 1 DNA Structure and Function
Protein Factory
What is the role of DNA and RNA in
building proteins?
• To build proteins, some of the information in the
DNA is copied to a separate molecule called RNA,
or ribonucleic acid.
• RNA is used to build proteins.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 7 Lesson 1 DNA Structure and Function
What is the role of DNA and RNA in
building proteins?
• Like DNA, RNA has a sugar-phosphate backbone
and the bases adenine (A), guanine (G), and
cytosine (C).
• Instead of thymine (T), RNA contains uracil (U).
• There are three types of RNA. Each type has a
special role in making proteins.
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Unit 7 Lesson 1 DNA Structure and Function
What is the role of DNA and RNA in
building proteins?
• When a cell needs to make a protein, it makes an
RNA copy of a section of the DNA. This is called
transcription.
• In transcription, DNA is used as a template to
make a complementary strand of messenger RNA
(mRNA).
• The information in the mRNA is then used to build
proteins. This is called translation.
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Unit 7 Lesson 1 DNA Structure and Function
What is the role of DNA and RNA in
building proteins?
• In translation, the mRNA passes through a protein
assembly line within a ribosome.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 7 Lesson 1 DNA Structure and Function
What is the role of DNA and RNA in
building proteins?
• A ribosome is a cell organelle made of ribosomal
RNA (rRNA) and protein.
• As mRNA passes through, transfer RNA (tRNA)
delivers amino acids to the ribosomes.
• The order of the bases codes for which amino acid
is attached.
• The amino acids are joined together to form a
protein.
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