Download Molecular Genetics

Chapter 12 Molecular Genetics
12.2 Replication of DNA
Unwinding
 DNA helicase, an enzyme, is responsible for
unwinding and unzipping the double helix.
 RNA primase adds a short segment of RNA,
called an RNA primer, on each DNA strand.
Chapter 12 Molecular Genetics
Chapter 12 Molecular Genetics
12.2 Replication of DNA
Comparing DNA Replication in Eukaryotes
and Prokaryotes
 Eukaryotic DNA unwinds in multiple areas
as DNA is replicated.
 In prokaryotes, the circular DNA strand is
opened at one origin of replication.
Chapter 12 Molecular Genetics
12.3 DNA, RNA, and Protein
Central Dogma
 RNA
 Contains the sugar ribose and the
base uracil
 Usually is single stranded
Chapter 12 Molecular Genetics
12.3 DNA, RNA, and Protein
Messenger RNA (mRNA)
 Long strands of RNA nucleotides that are
formed complementary to one strand of DNA
Ribosomal RNA (rRNA)
 Associates with proteins to form ribosomes
in the cytoplasm
Transfer RNA (tRNA)
 Smaller segments of RNA nucleotides that
transport amino acids to the ribosome
Chapter 12 Molecular Genetics
12.3 DNA, RNA, and Protein
Chapter 12 Molecular Genetics
12.3 DNA, RNA, and Protein
Transcription
 Through transcription,
the DNA code is
transferred to mRNA
in the nucleus.
 DNA is unzipped in
the nucleus and RNA
polymerase binds to a specific section where an
mRNA will be synthesized.
Chapter 12 Molecular Genetics
Chapter 12 Molecular Genetics
12.3 DNA, RNA, and Protein
The Code
 Experiments during the 1960s demonstrated
that the DNA code was a three-base code.
 The three-base code in DNA or mRNA is
called a codon.
Chapter 12 Molecular Genetics
12.3 DNA, RNA, and Protein
Translation
 In translation, tRNA
molecules act as the
interpreters of the mRNA
codon sequence.
 At the middle of the folded
strand, there is a three-base
coding sequence called the
anticodon.
 Each anticodon is
complementary to a codon
on the mRNA.
Chapter 12 Molecular Genetics
12.3 DNA, RNA, and Protein
Chapter 12 Molecular Genetics
Chapter 12 Molecular Genetics
Chapter 12 Molecular Genetics
12.4 Gene Regulation and Mutation
Eukaryote Gene Regulation
 Controlling transcription
 Transcription factors ensure that a gene
is used at the right time and that proteins
are made in the right amounts
 The complex structure of eukaryotic DNA
also regulates transcription.
Chapter 12 Molecular Genetics
12.4 Gene Regulation and Mutation
Mutations
 A permanent change that occurs in a cell’s
DNA is called a mutation.
 Types of mutations
 Point mutation
 Insertion
 Deletion
Chapter 12 Molecular Genetics
12.4 Gene Regulation and Mutation
Chapter 12 Molecular Genetics
Chapter 12 Molecular Genetics
12.4 Gene Regulation and Mutation
Protein Folding and Stability
 Substitutions also can lead to genetic
disorders.
 Can change both the folding and stability
of the protein
Chapter 12 Molecular Genetics
12.4 Gene Regulation and Mutation
Causes of Mutation
 Can occur spontaneously
 Chemicals and radiation also can
damage DNA.
 High-energy forms of radiation, such as X rays
and gamma rays, are highly mutagenic.
Chapter 12 Molecular Genetics
12.4 Gene Regulation and Mutation
Body-cell v. Sex-cell Mutation
 Somatic cell mutations are not passed on
to the next generation.
 Mutations that occur in sex cells are passed
on to the organism’s offspring and will be
present in every cell of the offspring.