Download Chapter 3, Section 4 The DNA Connection

Chapter 3, Section 4
The DNA Connection
Monday, November 16, 2009
Pages 107 -- 112
Objectives
• Explain the term “genetic code”.
• Describe the process by which a cell
produces proteins.
• Describe the different types of
mutations and how they affect
organism.
Vocabulary Words
• Messenger RNA
• Transfer RNA
• Mutation
Review…
• The main function of genes is to control
the production of proteins in the
organism’s cells.
• Proteins help to determine the size,
shape, and many other traits of an
organism.
• DNA is the major component of
chromosomes.
Review--cont’d…
• A DNA molecule is made up of four
different nitrogen bases (A, T, G, C).
• Nitrogen bases for the rungs of the DNA
ladder.
• A single gene on a chromosome may
contain anywhere from several hundred
to a million or more bases.
Genetic Code
• The order of the nitrogen bases along a gene
forms a genetic code that specifies what type
of protein will be produced.
• In the genetic code, a group of 3 bases code
for the attachment of a specific amino acid.
• The order of these bases determine the type
of protein.
Protein Synthesis
• Protein synthesis the process in which
protein is produced.
• During protein synthesis, the cell uses
information from a gene on a
chromosome to produce a specific
protein.
• Protein synthesis occur on the
ribosomes in the cytoplasm of the cell.
The Role of RNA
QuickTime™ and a
decompressor
are needed to see this picture.
• RNA is the genetic
messenger that
carries the genetic
code from the DNA
inside the nucleus to
the cytoplasm.
• Physically, RNA
looks like half a
ladder.
RNA vs. DNA
• Looks like half a ladder.
• Contains a different sugar molecule.
• Nitrogen base is different.
• RNA contains uracil instead of thymine.
RNA
• There are 2 types of RNA involved in
protein synthesis.
• Messenger RNA
• Copies the code message from the DNA in the
nucleus and carries the message into the
cytoplasm.
• Transfer RNA
• Carries amino acids and adds them to the
growing protein chain.
Protein Synthesis
Protein
Amino Acid
Protein
DNA
Ribosome
Transfer RNA
Nucleus
Messenger RNA
Messenger RNA
Mutations
• A mutation is any change that occurs in
a gene or chromosome.
• Mutations can cause a cell to produce
an incorrect protein during protein
synthesis.
• Result:
• The phenotype will be different than
expected.
Types of Mutations
• Mutations occurring protein synthesis.
• Substitution of a nitrogen base
• DNA replication process
• Incomplete separation during meiosis.
• Mutations in a body cell.
Effects of Mutations
• A source of genetic variety.
• Some changes are harmful to the organism.
• It reduces the organism’s chances for survival and
reproduction.
• Example: Cancer.
• Some changes are helpful.
• Improves an organism’s chances for survival and
reproduction.
• Some changes are neither harmful nor
helpful.
Homework
• Workbook 3.4 (due 11/18)
• Vocabulary quiz 3.4 (11/18)