Download IV. DNA connection A. genetic code 1. genes function to control

October 25, 2012
IV. DNA connection
A. genetic code
1. genes function to control protein
production
2. proteins determine
a. traits
b. size
c. shapes
3. DNA has four N bases
4. a single gene on a chromosome may
contain several hundreds to millions of
bases
5. order of bases form your genetic code
that determines what proteins are
produced
6. amino acids are the building blocks of
proteins
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B. cells make proteins
1. production of proteins is protein
synthesis
2. protein synthesis
a. is where cells use the information on
the genes to produce the protein
b. takes place on the ribosome in the
cytoplasm
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3. role of RNA
a. ribonucleic acid carries the genetic
code from the DNA
b. RNA contains different sugar than
DNA
c. RNA and DNA have different N
bases, (there is NO thymine in RNA - it is
replaced with Uracil)
d. types of RNA
1. messenger RNA copies DNA and
carries it to the cytoplasm
2. transfer RNA carries the amino
acid and adds to growing proteins
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Protein Synthesis
1. DNA molecule unzips
2. RNA bases match up along DNA strands (Uracil
replaces Thymine)
3. Genetic information in DNA transferred to mRNA
strand
4. mRNA leaves nucleus and enters cytoplasm
5. mRNA attaches to a ribosome and gives it the
code for the protein molecule that will form.
(The
ribosome will move along the mRNA strand)
6. tRNA attach to mRNA and read the message by
pairing up 3-letter codes to bases on mRNA
7. The order of amino acids (molecules that make
up proteins) is determined by the order of
the 3letter codes on mRNA
8. Protein molecule grows longer as tRNA puts the
amino acid it carries onto the protein chain.
9. Once the amino acid attaches to protein chain,
the tRNA releases and goes back to cytoplasm.
10. Each tRNA always picks up the same kind of
amino acid.
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Protein Chain
Amino
Acid
mRNA
Amino
Acid
Amino
Acid
Amino
Acid
Ribosome
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3.4 Section Review
1. a) What is the relationship between a gene, a DNA
molecule, and a protein?
A gene is the part of a DNA molecule that codes for a
certain protein.
b) How does a DNA molecule determine the structure of a
specific protein?
The sequence of bases on the DNA molecule codes for the
sequence of bases on messenger RNA, which codes for the
sequence of amino acids in the protein.
c) The DNA base sequence GGG codes for the amino acid
proline. Could this same base sequence code for a different
amino acid? Why or why not?
No, each three-letter code specifies one type of amino
acid.
2. a) List the sequence of events that happens during protein
synthesis.
Messenger RNA is produced using a strand of DNA as a
pattern and moves into the cytoplasm where it attaches to a
ribosome. There each three-letter code of
bases in the mRNA is matched to the tRNA that carries
the specified amino acid. The amino acids are attached in a
correct sequence to form a protein molecule.
b) What is mRNA? Describe how it performs its functions.
It is RNA that copies the coded message from the DNA in
the nucleus and carries the message to the ribosome in the
cytoplasm.
c) Does tRNA perform its function in the nucleus or
cytoplasm? Explain your answer.
The cytoplasm; it carries amino acids to the ribosome and
“reads” the mRNA.
3. a) How does a mutation in a gene affect the order of DNA
bases?
A base may be substituted for another; one or more bases
may be removed; bases may be added.
b) How can a mutation in a gene cause a change in an
organism’s phenotype?
The phenotype of the organism may be different as a result
of the incorrect protein.
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