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DNA Replication
Structure of the DNA in the cell
 Must pack between 1and 3 meters into each
cell (except RBCs)
 Uses a “coiled-coiled strucure”
 DNA wound around histones
 Histones cluster into Nucleosomes
Mechanism of Replication
 http://www.johnkyrk.com/DNAreplication.htm
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DNA  mRNA
Transcription
RNA vs. DNA
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DNA
Deoxyribose
Double Stranded
G, C, A, T bases
Durable
RNA
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Ribose
Single Stranded (Usually)
G, C, A, U bases
Fragile
Types of RNA
 Ribosomal RNA
(rRNA)
 Transfer RNA (tRNA)
 Messenger RNA
(mRNA)
Transcription
 In the nucleus
 RNA polymerase
 ONLY ONE SIDE OF
DNA IS USED AS A
TEMPLATE
 RNA is edited by
removing introns
 Transcription YouTube
Differences in Prokaryotes and
Eukaryotes
Prokaryotes
 Genome is small and
circular
 mRNA is ready for
immediate use
Eukaryotes
 DNA is found in
chromosomes and large
 Some pieces of DNA
have protein information
(exons)
 Some pieces are used for
regulation or have an
unknown use (introns)
mRNA Translation
RNAProtein
RNA Splicing
1.
mRNA is transcribed as
a whole transcript
2. Introns = DNA or RNA
that does not have
information for protein
3. Exons = DNA or RNA
DNA or RNA containing
information for proteins
4. Must splice out introns
for RNA to function
mRNA Splicing
 mRNA BINDS TO A RIBOSOME
 mRNA IS READ AND CONVERTED TO
A SPECIFIC AMINO ACID SEQUENCE
 mRNA CODES FOR AMINO ACID
 tRNA BRINGS AMINO ACID TO
RIBOSOME
 ANTICODON PAIRS WITH CODON AND
BINDS WHILE AA ARE BONDED BY
ENZYMES--INTO A PROTEIN CHAIN.
 RNA to Protein
 INFINITE VARIETY OF PROTEINS
CAN BE SYNTHESIZED FROM THE
20 AMINO ACIDS. (ANY ORDER &
ANY NUMBER OF AA)
 THE SEQUENCE OF AA IN A
PROTEIN DETERMINES THE
CHARACTERISTICS OF THAT
PROTEIN.
MUTATION!!!
MUTATION!!!!
Gene Mutations
 Point Mutation: change of a single
nucleotide
1. substitution
2. insertion
3. deletion
 Substitution Example
 Frameshifts: Insertions and Deletions
-shift reading of three letter words (codons)
THE CAT ATE THE RAT AND WAS FAT
-Remove the first C of CAT (deletion)
THE ATA TET HER ATA NDW ASF (ignore
AT)
-Add and E to THE
THE ECA TAT ETH ERA TAN DWA SFA
(ignore T)
Chromosomal Mutations
 Overall change in the number or structure of
chromosomes
 Changes in number of chromosomes
- Aneuploidys : loss or gain of a whole
chromosome
e.g. Trisomy 21 Down’s Syndrome 47, X_,+21
Rearrangement of Single
Chromosomes