
When a cell divides, forming new
cells, a complete set of genetic
instructions is generated for each
new cell. And when an organism
reproduces, genetic instructions pass
from one generation to the next.

DNA replication-process of
copying DNA molecules
Semi conservative replicationparental strands of DNA separate,
serve as templates, and produce
DNA molecules that have one
strand of parental DNA and one
strand of new DNA.
During DNA replication, the two strands of
the original parent DNA molecule, shown
in blue, each serve as a template for making
a new strand, shown in yellow. Replication
results in two daughter DNA molecules,
each consisting of one original strand and
one new strand.
 Unwinding=DNA
helicase
(enzyme) is responsible for
unwinding and unzipping the
double helix.

Base Pairing=The enzyme DNA
polymerase catalyzes the
addition of appropriate
nucleotides to the new DNA
strand.

Joining= in eukaryotic DNA there
are many areas along the
chromosome where replication
begins. When the RNA primer has
been replaced, the DNA LIGASE
links the 2 sections together.

One Gene, One Polypeptide
 Information Flow:
 DNA to RNA to Protein
 So what is the connection between
these genes and the polypeptide cells?
*The answer is RNA
(ribonucleic acid)

RNA
 Sugar is ribose
 Contains a nitrogenous base called
URACIL (U) instead of thymine of
DNA
 RNA typically forms a single,
sometimes twisted strand, not a double
helix like DNA

Several RNA molecules play a part
in the intermediate steps from gene
to protein.
 In the first step, DNA’s nucleotide
sequence is converted to form a
single-stranded RNA molecule in a
process called TRANSCRIPTION.


A three base code in DNA or mRNA
Each of the three bases of a codon in the DNA
is transcribed in to the mRNA code.
Figure 14 on page 338.
 We will practice using it tomorrow


The next step , however, requires
changing languages. Genetic
TRANSLATION converts
nucleic acid language into amino
acid language.