Download Unit D : DNA -Functions of DNA - Mr. Lesiuk

Unit D : DNA -Functions of DNA
1. Replicates (duplicates) itself so each new cell
has a complete, identical copy.
2. Controls the activities of a cell by producing
proteins. The combination of proteins
determines the characteristics (phenotype) of
each living organism.
3. Undergoes occasional mutations. (Mistakes in
replication) which accounts for the variety of
living things on Earth.
DNA Replication :
1. The DNA molecule becomes untwisted by an
enzyme called "Helicase"; breaking the hydrogen
bonds. The 2 strands that make up DNA become
unzipped. Each side acts as a template. (ie. The
weak hydrogen bonds between the paired bases
are broken by an enzyme)
2. New complimentary nucleotides, always
present in the nucleus, move into place and pair
with complementary bases on the exposed strands.
- T joins to A
- C joins to G
3. The adjacent nucleotides, through their sugarphosphate components become joined together
along the newly forming chain. The enzyme DNA
polymerase helps this. (Adds nucleotides to
template).
4. When the process is finished, 2 complete DNA
molecules are present, identical to each other and
to the original molecule.
5. Both DNA will now wind back up into their
helical shape.
- DNA replication is called semiconservative
because each new double helix is composed of an
old (parental) strand and a new (daughter) strand.
****** SEE DIAGRAMS BELOW
DNA – REPLICATION
ILLUSTRATED