Today: How
do genes
work?
Discussions
begin/began
this week.
Fig 15.3
Information
flow in cells
Protein
Chains of DNA can store information:
Fig 4.6, .7
Each chain of
DNA is made
of individual
units =
nucleotides
Fig 3.8
Proteins are the
“doers” of the cell.
They act as:
•Enzymes
•Structural Support
•Transporters
•Signals
Proteins are a
string of amino
acids
Amino acids connect together to make proteins.
Tbl 3.3
The relationship between DNA and genes
a gene - DNA used to produce RNA or protein
promoter
coding region
terminator
non-gene
DNA
DNA Composition:
In humans:
•Each cell contains ~6 billion nucleotides of
DNA.
•This DNA is ~2 meters long and 2 nm wide.
•~98% does not directly code for amino acids
•In a single human cell only about 3-5% of
genes are expressed at a time.
DNA Composition:
In humans:
•Each cell contains ~6 billion base pairs of
DNA.
•This DNA is ~2 meters long and 2 nm wide.
•~1.5% directly codes for amino acids
•~25% is genes
•In a single human cell only about 5-10% of
genes are expressed at a time.
The relationship between DNA and genes
a gene - DNA used to produce RNA or protein
promoter
coding region
terminator
non-gene
DNA
Five Perspectives about Genes:
1.Genes act as units of heredity
2.Genes are seen as a cause of
disease
3.Genes code for proteins
4.Genes act as switches, controlling
development
5.Genes are replicators (selfish gene)
Visualizing the perspectives about genes
Fig 14.2
Different strains of
bacteria are injected
into mice.
Visualizing the perspectives about genes
Fig 14.2
Fig 14.2
Visualizing the perspectives about genes
Fig 14.2
Visualizing the perspectives about genes
What has happened to the
bacteria?
• What part of the cell contains/transfers
the information?
Fig 14.3
Fig 14.2
Visualizing the perspectives about genes
1. Genes act as units of heredity
2. Genes are seen as a cause of disease
3. Genes code for proteins
4. Genes act as switches, controlling
development
5. Genes are replicators (selfish gene)
In cells, DNA is a double-stranded helix
Fig 14.7
Five Definitions of Genes:
1. Genes act as units of heredity
2. Genes are seen as a cause of disease
3. Genes code for proteins
4. Genes act as switches, controlling
development
5. Genes are replicators (selfish gene)
4 nucleotides
in DNA
?
20 amino acids in proteins
Fig 15.6
How can 4 nucleotides code for 20 amino acids?
If
Ratio
(nucleotide:amino acid) Possible combinations
1:1
41 4
Fig 15.6
How can 4 nucleotides code for 20 amino acids?
If
Ratio
(nucleotide:amino acid) Possible combinations
1:1
41 4
2:1
42 16
Fig 15.6
How can 4 nucleotides code for 20 amino acids?
If
Ratio
(nucleotide:amino acid) Possible combinations
1:1
41 4
2:1
42 16
3:1
43 64
Fig 15.6
How can 4 nucleotides code for 20 amino acids?
If
Ratio
(nucleotide:amino acid) Possible combinations
1:1
41 4
2:1
42 16
3:1
43 64
•There are more possible combinations than
amino acids.
Combinations of
3 nucleotides
code for each 1
amino acid in a
protein.
Fig 15.8
the Genetic Code
Fig 16.21
Changes in DNA can change the protein
Fig 16.21
Changes in
DNA can
change the
protein
The fat cat ate the rat.
change one letter
The zat cat ate the rat.
The fat cat ate the rat.
change one letter
The zat cat ate the rat.
delete one letter
The atc ata tet her at.
Combinations of
3 nucleotides
code for each 1
amino acid in a
protein.
Fig 16.10
How is
DNA used
to make
proteins
and RNA?
Protein
Both
proteins
and RNA
are
involved
in the
processes.
Differences between
DNA and RNA
Fig 4.1
Fig 16.10
How is
DNA used
to make
proteins
and RNA?
Protein
Both
proteins
and RNA
are
involved
in the
processes.
Fig 16.10
Genes act as
switches.
The information
in genes is what
to make and
when to make it.
Protein
Genes have three basic parts
a gene
promoter
coding region
terminator
non-gene
DNA
Fig 16.10
Genes contain
the information
to make RNA
and/or proteins.
Genes act as
switches.
The information
in genes is what
to make and
when to make it.
Protein
For life to exist,
the information
(genes) must be
passed on.
1. Genes act as units of
heredity
5. Genes are replicators
(selfish gene)
Fig 11.1