Download 9/11

DNA
Structure
and
Function
•Homework #1
is posted and
due 9/20
•Bonus #1 is
posted and due
10/25
How is information transferred between cells?
Fig 7.2
Different strains of
bacteria are injected
into mice.
How is information transferred between cells?
Fig 7.2
How is information transferred between cells?
Fig 7.2
How is information transferred between cells?
Fig 7.2
Fig 7.2
What has happened to the
bacteria?
• DNA is the
transforming agent
Fig 7.3
The Structure
of DNA
If these
two can
win a
Nobel
prize…
James Watson
and
Francis Crick
Rosalind Franklin
Data showing uniformity of DNA
structure.
Fig 7.5+8.2
Nucleotides have a sugar backbone
Fig 7.5 +8.2
This subtle difference in structure has
profound effects.
Fig 7.5+8.2
Plus four different bases
Together with a phosphate = nucleotide
Fig 7.5
Fig 7.5
Together with a phosphate = nucleotide
Fig 7.8
Connect nucleotides by
covalent bond = strand
Fig 7.8
DNA is typically
double stranded
The strands are
connected by
hydrogen bonds
Rosalind Franklin
Data showing uniformity of DNA
structure.
• Base pairing in DNA
Figure 7-10
Fig 7.8
• Two representations of the DNA double helix
Figure 7-9
Fig 7.9
Fig 8.11
DNA stores
information, but
does not do
anything. The
information must be
expressed to be
useful.
The relationship between DNA and genes
a gene
promoter
coding region
terminator
non-gene
DNA
DNA Composition:
In humans:
•Each cell contains ~6 billion base pairs of
DNA.
•This DNA is ~2 meters long and 2 nm wide.
•~97% does not directly code for amino acids
•In a single human cell only about 3-5% of
genes are expressed at a time.
Length of
human DNA
in each cell
Width of DNA
DNA Composition:
In humans:
•Each cell contains ~6 billion base pairs of
DNA.
•This DNA is ~2 meters long and 2 nm wide.
•~3% directly codes for amino acids
•~10% 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
of a Gene
Genes act as units of heredity…storing and
passing on information.
Genes act as
units of
heredity…
storing and
passing on
information.
Genes are seen as a cause of disease
Genes are seen as a cause of disease
Sickle-cell anemia is caused by a single nucleotide
Fig 6.5
change in the hemoglobin gene
Fig 8.11
Genes code for
proteins
Genes code for proteins…
Proteins are the “doers” of the cell.
They act as:
•Enzymes
•Structural Support
•Transporters
•Signals
Genes act as switches, controlling development
Genes act as switches, controlling development
Genes are replicators
(selfish gene)
From “Biology 7th ed.”
by Campbell et al
fig 19.14
Fig 5.25
Viruses infect
living cells, take
over, and produce
more virus.
Bodies are vessels for the transmission of genes
Five Perspectives 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)
Transposons
Genes are replicators (selfish gene)
Transposons: mobile DNA
Barbara McClintock, discoverer of transposons
Transposons are self-moving DNA
Fig 14.8
Fig 14.8
Transposons move
within genomes via the
action of transposase
Fig 14.4
transposase
transposon
Fig 14.4
Fig 14.4
Fig 14.4
Fig 14.4
Genes are replicators
(selfish gene)
From “Biology 7th ed.”
by Campbell et al
fig 19.14
Genes are replicators (selfish gene)
Transposons: mobile DNA
Five Perceptions 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)
We did NOT cover this in class. I left it
in if you are interested in learning more
about it. This article in Nature has
some good info:
The RNA World
pg 312
Fig 7.5 +8.2
This subtle difference in structure has
profound effects.
Fig 7.8
Connect nucleotides by
covalent bond = strand
(notice 5’-3’ bond)
Fig 8.11
DNA stores
information, but
does not do
anything. The
information must be
expressed to be
useful.
Fig 8.11
Where did this
system come from?
Was RNA the first biological molecule?
The RNA World
pg 312
Living organisms must fit all of the following
criteria: (modified from Campbell “Biology”)
1. They must have organization.
2. They must have metabolism.
3. They must respond to the environment.
4. They must be able to reproduce themselves.
Fig 8.2
U*
RNA structure
A
G
C
RNA can form base
pairs within single
stranded molecule
Fig 8.10+9.12
RNA can form complex 3-D structures
Ribosomes (rRNA) have enzymatic activity:
Enzymatic RNA=ribozyme
Fig 9.12
Some RNA molecules have catalytic activities
pg 223
Living organisms must fit all of the following
criteria: (modified from Campbell “Biology”)
1. They must have organization.
2. They must have metabolism.
3. They must respond to the environment.
4. They must be able to reproduce themselves.
RNA can (theoretically) be replicated
using complementary bases
Experimental
determination of RNA’s
ability to
self-ligate…
A step towards selfreplication
from Freeman’s “Biological
Science” (2002) chapter 3
Q: Can RNA selfligate?
Hypos:
Yes.
No.
from Freeman’s “Biological
Science” (2002) chapter 3
Column Chromatography
RNA’s added in
aqueous
solution
Some, with tag,
bind to column
Without tag,
flow thru
Overall RNA self-ligation
improves by selection
Theoretical
evolution of
self-replicating
RNA
Hypothetical Origin of Life
pg 214