Watson
and Crick/ Rosalind
Franklin
The DNA
molecule has a sugar-phosphate backbone with base-pairing on its interior, and
is twisted into a double helix (Fig. 12.4c). The nucleotide base pairs are adenine - thymine (A-T) and guanine - cytosine (G-C). Fig. 12.3
How the DNA Molecule Replicates (Fig. 12.9) Prokaryote
movie. Movie
2
Each individual chain of a DNA molecule is
complementary to its pair. Fig.
12.7. ATTGCAT/TAACGTA
DNA polymerase
DNA molecule "unzips" with the
enzyme helicase
replication fork.
Leading and lagging strands Fig. 12.8
ligase.
Mutation Table 12.1
Germ-line tissues
Somatic tissues
Altering the sequence of DNA Fig 12.11
Changes in gene position
The
Importance of Genetic Change in Germ-line tissue
Evolution can be viewed as the natural selection
of particular combinations of alleles from a pool of alternatives.
Genetic change through mutation and recombination provides the raw material for
evolution.
From
Gene to Protein (Image)
Step 1 is transcription, the production of messenger RNA (mRNA)
The Transcription Process (Fig. 13.1) Movie
Transcription
RNA polymerase
promoter
strand of mRNA
complementary
The
Genetic Code Fig. 13.2
The mRNA sequence that corresponds to the three-nucleotide
sequence on DNA is called a codon.
Step 2 is translation Movie.
Ribosomes (Fig. 13.3)
Transfer RNA (tRNA) (Fig.
13.4)
anticodon,
Making
the Protein (Fig.13.5)
Ribosomes guide the translation process Fig. 13.6
Processing eukaryotic DNA
Fig. 13.8
Overview: from DNA to protein Fig 13.10
Turning a
gene on or off
DNA
methylation - turns genes off permanently
Blocking
access to the DNA by RNA polymerase
Fig. 13.14
RNA
interference or gene silencing
