7th Grade Life Science
Mr. Fisk
Chapter 4 - Genetics: The Science of Heredity
Engage – Discover Activity – Page 131
Objectives:
1. Explain what forms the genetic code.
2. Describe how a cell produces proteins.
3. Identify how mutations can affect an
organism.
4-4 The DNA Connection
A. The Genetic Code
1. The main function of genes is to control the
production of proteins in an organism.
Proteins help to determine the size, shape,
color, and many other traits.
2. Genes and DNA
 Each chromosome contains thousands of
genes.
 1 gene may contain several hundred to a
million or more bases.
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7th Grade Life Science
Mr. Fisk
3. Order of Bases
 The sequence of bases in a gene forms a
code that tells the cell what proteins to
make.(ATGACGTAC)
 Proteins are made of amino acids.
 A group of 3 DNA bases = Specific Amino
Acid ( EX. CGT = Alanine)
B. How Cells Make Proteins
1. Protein Synthesis – The cell uses info.
from a gene on a chromosome to
produce a specific protein.
 Occurs on ribosomes in cytoplasm.
2. Role of RNA – Messenger – carry
genetic code from nucleus into
cytoplasm.
3. Types of RNA –
 Messenger RNA – copies code from
DNA
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7th Grade Life Science
Mr. Fisk
 Transfer RNA – carries amino acids to
ribosomes and adds them to the
growing protein.
4. Translating code – page 134-135
C. Mutations
1. Mutation – any change in a gene or
chromosome.
2. Body cells not passed on.
Sex Cells passed on.
3. Types of Mutations
 Single base may be substituted for
another.
 Chromosomes do not separate
correctly during meiosis.
4. Effects of Mutations
 Genetic variety
 Harmful mutations – Albino Deer
 Helpful mutations – Resistant bacteria
to antibiotics.
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