Transcript Genetics Chapter Twelve: The Code of Life • 12.1 The Role of DNA in Heredity • 12.2 DNA and Technology.

Genetics
Chapter Twelve: The Code of Life
• 12.1 The Role of DNA in Heredity
• 12.2 DNA and Technology
Investigation 12A
The DNA Molecule
• What is the structure of the DNA molecule?
12.1 The role of DNA in heredity
• A DNA molecule
looks like a twisted
ladder.
• Its shape is called
a double helix.
12.1 The role of DNA in heredity
• The two sides of the DNA ladder are made of
sugar molecules alternating with phosphate
molecules.
Can
you pronounce the names
•of
The
rungs
of the
DNA molecule are made of
the
four
bases?
chemical building blocks called bases.
• The four bases found in DNA are adenine (A),
thymine (T), cytosine (C), and guanine (G).
12.1 DNA replication
• DNA replication is
the process of a
DNA molecule
making a copy of
itself.
12.1 DNA replication
• DNA replication
ensures that each
daughter cell has
an exact copy of
the DNA from the
parent cell.
12.1 DNA replication
1. Replication begins with the partial unwinding of
the double helix.
2. The base pairs separate.
3. A special molecule moves along each original
strand of DNA and “reads” the bases.
4. A new strand is assembled along each original
strand. (New pieces come from the cytoplasm.)
5. The strands re-twist and two daughter molecules
are produced.
12.1 Protein synthesis
• In total, the DNA in
one of your cells
contains about 3
billion base pairs!
• The order of base
pairs along a gene
is called its base
sequence.
What is the base sequence
of this gene segment?
12.1 Protein synthesis
• Genes control the
production of proteins.
• For example, the color of
your eyes is determined
by a protein.
• The production of proteins
in the cell is called
protein synthesis.
12.1 Protein synthesis
•
•
•
The order of base pairs along a gene forms a
code that tells a cell which protein to make.
Sets of three bases along a strand of DNA form
three-letter codes that tell the cell which amino
acids make up the protein.
There are 20 different amino acids, so these
amino acids can be put together in many ways to
make millions of different proteins!
12.1 Protein synthesis
1. Messenger RNA copies the gene and
carries it out of the nucleus.
2. Transfer RNA from the cytoplasm decodes
the three letters.
3. Transfer RNA matches the right amino acid
to messenger RNA sequence.
4. The amino acids are linked together on the
ribosome to form a protein strand.
12.1 Mutations
• A mutation is a
change in the
hereditary material of
an organism
• Mutations can
happen in any cell
and in any gene.
12.1 Genetic disorders
• A genetic disorder
is an abnormal
condition that an
organism inherits
from its parents.
One chromosome pair has a
mutated extra chromosome.
Can you find it?
12.1 Mutations
• Doctors use a procedure
called amniocentesis to
find out if a baby could have
Down’s syndrome.
• The doctor removes a small
amount of the fluid that
surrounds the developing
baby and examines the
chromosomes.