Chapter 5.4 Notes

1. Section 4: Genes, DNA,
and Proteins
• What forms the genetic code?
How does a cell produce proteins?
How can mutations affect an organism?
7.2.a Students know cells function similarly in
all living organisms.

2. The Genetic Code
• The main function of genes is to control the
production of proteins in an organism's cells.

3. Genes and DNA
• A single gene may contain anywhere from
several hundred to a million or more
nitrogenous bases.

4. Order of Bases
• The order of nitrogen bases along a gene
forms a genetic code that specifies what type
of protein will be produced.
• Proteins are long-chain molecules made of
individual amino acids.
• A group of three DNA bases codes for one
specific amino acid.
– Example: CGT = alanine

6. How Cells Make Proteins
• The production of proteins is
called protein synthesis.
• During protein synthesis, the
cell uses information from a
gene on a chromosome to
produce a specific protein.
• Take place on the ribosomes in
the cytoplasm.

7. The Role of RNA
• A messenger must carry the genetic code from
the DNA, in the nucleus, to the ribosome, in
the cytoplasm.
– mRNA
DNA RNA
sugar = deoxyribose sugar = ribose
two strands one strand
ATGC AUGC (uracil)

8. Types of RNA
• Messenger RNA – RNA
that copies the coded
message from DNA in
the nucleus and carries
the message into the
cytoplasm.
• Transfer RNA – RNA in
the cytoplasm that
carries an amino acid to
the ribosome and adds
it to the growing
protein chain.

9. HOW IS RNA
DIFFERENT
FROM DNA?
Reading Checkpoint

10. Translating the Code
1. DNA unzips
1. One strand directs the production of mRNA.
2. RNA bases pair up with DNA bases
1. A-U, T-A, C-G, G-C
2. mRNA leaves the nucleus
1. attaches to a ribosome
2. mRNA provides the code and ribosomes move along he strand
3. tRNA attach to the mRNA
1. tRNA “reads” the code on mRNA by pairing to the three letter
codes
2. tRNA also carries the specific amino acids – determined by the
order of the three-letter codes on the mRNA
4. The protein molecule grows larger as each amino
acid is added to the chain

11. During protein synthesis, the cell
uses information from a gene on a
chromosome to produce a specific
protein.
How Cells Make Proteins

13. In which organelle of the cell are proteins manufactured?

14. WHAT IS THE FUNCTION OF TRNA?
Reading Checkpoint

15. WHY IS IT IMPORTANT THAT PROTEIN
SYNTHESIS BE SO CAREFULLY
ORGANIZED?
Bonus Question

16. Mutations
• Mutation – A change in a gene or chromosome.
• Mutations can cause a cell to produce an
incorrect protein during protein synthesis.
• As a result, the organism’s trait, or phenotype,
may be different from what it normally would
have been.
• Mutations in body cells vs. sex cells

17. Types of Mutations
• Small changes can occur during DNA replication
single base substituted for another
one or more bases removed from a section of DNA
• Chromosomes don’t separate correctly during
meiosis
too many or too few chromosomes or an extra segment
of chromosomes

18. Mutations
Mutations can cause a cell to
produce an incorrect protein
during protein synthesis.
As a result, the organism’s
trait, or phenotype, may be
different from what it
normally would have been.

19. Effects of Mutations
• Source of genetic variety
• Mutations can be harmful, helpful, or neither
– Mutations are harmful if they reduce the
organism’s chance for survival and reproduction.
• Depends partly on environment.

20. WHAT ARE TWO TYPES OF
MUTATIONS?
Reading Checkpoint

21. WHAT KIND OF MUTATION MIGHT HELP
AN ANIMAL SURVIVE IN A DESERT?
Bonus Question