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DNA and RNA
Chapter 12
DNA History
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Griffith and Transformation:
 Studied pneumonia bacteria
 Isolated strains of bacteria from mice
 Disease causing: smooth colonies
 Harmless strand: rough edge colonies
Griffith’s Experiments
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Mice injected with the disease-causing bacteria = the
pneumonia, death
Mice injected with the harmless bacteria = live
Heat killed disease-causing bacteria = Mice survived
Mix heat killed disease-causing bacteria and harmless
live bacteria = pneumonia, death
Transformation
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What happened????
Transformation: one strain of bacteria changes
permanently into another
The harmless bacteria took in material from
the dead disease-causing bacteria and it
became a part of it.
DNA and Chromosomes
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Prokaryotic cells lack
organelles
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DNA is located in the
cytoplasm
Eukaryotic cells contain
organelles
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Located in the nucleus
DNA - The Double Helix
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Watson and Crick 1953 - Built a 3-D model
DNA composition - 2 long chains of
nucleotides held by hydrogen bonds
Looks like a twisted ladder or spiral staircase.
Nucleotide: made up of a 5-carbon sugar, a
phosphate group, and a nitrogenous base
DNA Bases A=T and C =G (Base Pairing)
Sugar in DNA = Deoxyribose
DNA Replication
makes more DNA for new cells
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Replication occurs before cell division in
Interphase (in “S”)
Each strand of DNA has information needed to
make the other “complementary”
First – An enzyme called Helicase separates
the double helix
Replication forks: sites where separation and
replication occur
DNA polymerase
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Next we assemble complementary strands
DNA polymerase: is the enzyme involved in
assembling nucleotides to produce a new DNA
strand
It also proof reads each new DNA strand
Differences in DNA and RNA
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DNA:
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Sugar: Deoxyribose
Double stranded
Contains Thymine
Used to make more
DNA and to make RNA
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RNA:
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Sugar: Ribose
Single stranded
Contains Uracil
Used to make Proteins
Structure of RNA
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Consists of a single
strand of nucleotides
Sugar is Ribose
Nitrogen bases
A = U and C = G
Involved in making
proteins
Types of RNA
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Three types:
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Messenger RNA (mRNA): carries copies of DNA
instructions to make proteins
Ribosomal RNA (rRNA): “meeting place” where
proteins are made
Transfer RNA (tRNA): transfers amino acids
according to coded messages on mRNA
Protein Synthesis (Making Protein)
Part 1: Transcription
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Takes place in the nucleus
DNA is broken apart by the enzyme Helicase
mRNA is produced by copying one side of the
DNA
RNA polymerase assembles “complementary”
nitrogen bases (A = U and C = G)
mRNA leaves the nucleus
Protein Synthesis Part 2:
Translation
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Takes place on the ribosome (site of protein
synthesis)
mRNA goes to the “meeting place” or
ribosome
The mRNA message is decoded if the code
matches tRNA
If the codes match tRNA drops off an amino
acid which link to form a Polypeptide chain (or
a protein)
Protein Synthesis Summary
Terms to Know
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Codon: three bases on mRNA that code for a
single amino acid
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EX: UACGAGACA
Read as: UAC GAG ACA
Anti-codon - three bases on tRNA that must
match the codon to join amino acids
There are 64 possible three-base codons
Start codon: begins the process of translation
Stop codon: stops the process of translation
mRNA CodonChart
(to code for amino acids)
When Copying Goes Wrong Mutations
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Gene mutations: mutations that produce
changes in a single gene
Point mutations: gene mutations involving
changes in one or a few nucleotides
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Include:
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Substitution: one base is changed to another
Insertions: an extra base pair is inserted
Deletion: a base pair is deleted
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Frameshift Mutations:
gene mutations that shift
the reading frame of the
genetic message.
Chromosomal Mutations
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Changes in the number or structure of chromosomes
Four Types:
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Deletions: loss of all or part of a chromosome
Duplication: extra copy of parts of a chromosome
Inversion: reverse the direction of parts of chromosomes
Translocation: part of the chromosome breaks off and
attaches to another
CHAPTER 13 NOTES
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Selective breeding - allowing only those
animals with desired characteristics to produce
the next generation.
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Humans use selective breeding, to take
advantage of naturally occurring genetic
variation in plants, animals, etc..
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Inbreeding is the continued breeding of
individuals with similar characteristics.
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Inbreeding can lead to problems. Members
of a breed are genetically similar - there is
always a chance that a cross between two
individuals will bring together two recessive
alleles…for example joint deformities, etc.
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Breeders can increase the genetic variation
(differences) in a population by inducing
(causing) mutations, which are a source of
genetic variability (differences).
Changing the DNA Code
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Genetic engineering making changes in the
DNA code of a living organism.
Cutting Up DNA
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restriction enzymes cuts DNA at a specific
sequence of nucleotides.
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Restriction enzymes are used to edit DNA. The
enzyme cuts the molecule at specific
sequences. The cut ends are called sticky ends
which create complementary base sequences.
Analyzing DNA
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Gel (or DNA) electrophoresis DNA
fragments are placed at one end of a porous
gel, and an electric voltage is applied, the
DNA molecules move to the end of the gel
creating bands used to compare the genes for
relatedness.
DNA Fingerprinting
Genetic Engineering
Terms to Know
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recombinant DNA - taking a gene from one
organism and attach it to the DNA of another .
Transgenic – describes an organism that
contains genes from other species.
Hybridization - mating dissimilar individuals
to bring together the best of both organisms.
The organisms produced are called Hybrids.
A clone is a genetically identical cell produced
from a single cell.
Making More DNA For Analysis
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polymerase chain reaction (PCR) making
many copies of a particular gene for analysis.
Polymerase chain reaction (PCR) is used to
make multiple copies of genes. Just a few
cycles produces millions of copies.
PCR Virtual Lab
http://learn.genetics.utah.edu/content/labs/pcr/
Using Genetic Engineering To
Benefit Mankind…
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Transformation - a cell takes in DNA from
outside the cell. And incorporates it into it’s
DNA.
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plasmid - A circular piece of DNA in bacteria.
Used in transformation to create things like
human insulin and growth hormone.
Bacterial Transformation
Used in Making Human Insulin and Growth Hormone
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Genetic marker—gene that distinguishes
bacteria that carry foreign DNA from those
that don't.