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Goal 3
DNA, Protein Synthesis,
Genetics, Biotechnology
and Evolution
3.01 DNA, RNA and Protein
Synthesis
DNA is the code of life. It contains the
information on how to make
proteins.
Structure of DNA



DNA (deoxyribonucleic
acid)forms a doublehelix shape
Consists of a sugar
(deoxyribose), a
phosphate, and a
nitrogenous base
Bases
– Adenine-Thymine
– Guanine-Cytosine
(complementary base
pairing)
Nucleotide –building blocks of DNA
A nucleotide is made
up of a phosphate
group, nitrogen
base (A,T,G,C) and
sugar.
Hydrogen Bonds
Weak hydrogen
bonds attach the
two strands of the
DNA molecule.
DNA replication


Copying of genetic
material before
mitosis and meiosis
3 steps
– 1) DNA unzips at
hydrogen bonds
– 2) free nitrogenous
bases join up to newly
opened bases
– 3) sugar-phosphate
“backbone” rebuilt
The Code
Every three nitrogen bases is the
code for one amino acid.
An error in a nitrogen base is
called a mutation.
RNA
Ribonucleic Acid
Single strand.
Uracil instead of
thymine.
Ribose instead of
deoxyribose.
Types of RNA
Messenger RNA – carries DNA code
from nucleus to ribosome
(why can’t DNA leave the nucleus?)
Transfer RNA - carries amino acids
from the cytoplasm to the ribosome
Ribosomal RNA – what the ribosome is
made of
Protein Synthesis
Two Steps
Transcription – copying DNA code onto
the mRNA
Translation – making protein in the
ribosome
Protein Synthesis
Transcription –
DNA unwinds and
unzips
mRNA nucleotides
match up to the
complimentary
DNA nucleotide
Single strand of
mRNA is made with
the DNA code
Protein Synthesis
mRNA leaves the
nucleus and carries
the code to the
ribosome
Protein Synthesis
Translation –
mRNA lines up in the ribosome
mRNA triplet codes (codons)match up with
tRNA triplet codes (anticodons)
Protein Synthesis
Translation continued
Amino acids are put in correct sequence.
Peptide bond forms between amino acids.
Polypeptide folds into protein.
Protein
Reading and interpreting an mRNA
codon chart


Find each codon (3
base sequence)
from the mRNA
Use chart to find
the correct amino
acid that it codes
for
Gene Regulation
All cells of an organism have the same
DNA.
What type of cell develops depends on
which genes get turned on or off.
This is why a multicellular organism is
able to differentiate into many types
of cells. For example: skin cells,
muscle cells, bone cells.
Gene Regulation
Cells respond to their environment by
producing different types and amount of
protein.
Examples:
1. You get cut and your skin cells need to
make proteins to repair your skin.
2. Cancer may result when your cells make
too many cells (protein).
3. Diabetes may result if your pancreatic
cells don’t make enough insulin (protein).
3.02 Cell Division
2 Types of cell division:
1.
Mitosis – involved in growth, repair
and asexual reproduction
2.
Meiosis – involved in the production
of gametes
Examples of asexual reproduction
Binary fission
Asexual reproduction
Budding in
Hydra.
Asexual Reproduction
Cutting of a plant
Mitosis
 Occurs
in all body cells
 Results in 2 new genetically identical
daughter cells
 Maintains the chromosome number
 Chromosomes DOUBLE  then SPLIT
Example: humans 46 92 46
Stages of Mitosis
1.
2.
3.
4.
5.
DNA (chromosomes)
replicate
Spindle forms, nuclear
membrane disappears
Chromosomes line up
along the equator
Spindle fibers shorten,
bringing chromosomes
towards poles
Cytoplasm divides
Replicated chromosme

Replicated
chromosome is
actually two
identical
chromosomes
attached at the
centromere
Meiosis
 Occurs
only in the sex organs (testes
and ovaries)
 Results in 4 gametes (sex cells)
 Reduces the chromosome number in
half (for sexual reproduction)
 Chromosomes
DOUBLE SPLITSPLIT
Example: human 46924623
Stages of Meiosis
1.
2.
3.
4.
5.
DNA replicates
Chromosomes line
up along the
equator
Replicated pairs
split
Chromosomes line
up again
Centromere splits
Sources of variation
Crossing over (only
occurs during
meiosis).
Sources of Variation
Random
Assortment
Of
chromosomes
Sources of Variation

Gene mutation

Nondisjunction 

Fertilization
3.03 Patterns of Inheritance





Gregor Mendel
Father of genetics
Austrian Monk
First noticed
inheritance of traits
Studied heredity in
pea plants, and noted
statistics included
within
monohybrid/dihybrid
crosses
Mendel’s Experiments
Results of Mendel’s
crosses with pea
plants.
 He studied seven
different traits.

Genetic Vocabulary
Dominant- allele
which masks the
phenotype of other
alleles
 Recessive – allele
that will not be
expressed if
dominant allele is
present

Genetic Vocabulary
Heterozygous
(hybrid) – the
genes in
the gene
pair are
different
Homozygous
(pure) – the
genes are the
same
Genetic Vocabulary
Geneotype – The
actual genes of an
organism
Phenotype – What an
organism actually
looks like.
Genetic Vocabulary
Parental generation
F1 Generation
F2 Generation
Law of Segregation
During meiosis, the
gene pair splits
and each gamete
only has one
member of each
pair of
genes.
Law of Independent Assortment
During meiosis, the
genes in each gene
pair move into the
gametes
independently of
each other. Notice
you can still get a
3:1 ratio between
yellow and green
or round and
smooth.
Genotype and Phenotype
A change in the environment also can affect the phenotype.
Although we often think of flamingos as being pink, pinkness is
not encoded into their genotype. The food they eat makes
their phenotype white or pink
Test Cross
Mate unknown with a pure recessive.
B – black guinea pig
b – white guinea pig
Black guinea pig – BB or Bb?
BB x bb
Result: only black
offspring
Bb x bb
Result: black
and white pigs
Incomplete Dominance
Blending of two traits.
Incomplete Punnett Square
Co-dominance
Co-dominant alleles
result in the
expression of both
traits. Examples:
roan shorthorn
cattle of AB blood
Pedigrees






Tools used by
scientists to trace
inherited genes
through a family tree
Squares= male
Circle=female
Filled=affected
Half filled = carrier
Empty=not affected
Polygenic Traits
Traits which are
coded for by more
than one allele.
 Usually results in a
blending of traits
(ex: eye color, skin
color, hair color)

Polygenic – Skin color
Human Genetics
Examples of single
gene, autosomal
inheritance
patterns:
Sickle Cell Anemia
Cystic Fibrosis
Huntington’s Disease
Sickle Cell Anemia
Recessive
Predominantly in
people of
African/AfricanAmerican descent.
Hybrid individuals
are resistant to
malaria
Symptoms: tired,
pain in joints
Cystic Fibrosis
Recessive
Predominantly in
caucasians
Symptoms: mucous
clogs lungs and
other organs,
individuals usually
don’t live past 20
years old
Huntington’s Disease
Dominant
Symptoms:
Abnormal body
movements,
gradual deterioration
or loss of
intellectual abilities
(dementia),
behavior problems
Blood Types
A and B are
codominant.
O is recessive.
Punnett Square - Blood
Sex Linked Traits
Trait is more likely
to be inherited by
males
 Gene for these
traits are found on
the X chromosome,
but not the Y
because it is so
short
 Recessive

Sex Linked Traits
Hemophilia
 Defective gene
prevents the
normal formation
of the proteins for
clotting (platelets)
 Symptoms:
uncontrollable
bleeding when cut
Sex Linked Traits
Colorblindness
Unable to distinguish
between certain
colors. For
example –
red/green color
blindness
Karyotypes
What sex is this individual?
Karyotypes
What disease does this individual have?
3.04 Biotechnology
Human Genome Project
Scientists have
uncovered the
entire human DNA
code.
Information useful in
screening for
diseases, gene
therapy and
developing drugs.
Gene Therapy
Inserting corrected
gene into person
who has a
defective gene.
Still in the
experimental
stages.
Gel electrophoresis
DNA fragments separate
according to size
Gel Electrophoresis
Also called DNA
fingerprinting.
Used in crime
scene
investigations.
Used to determine
how closely related
organisms are.
Transgenic Organisms
Having DNA from
another species
 Example: a cow or
pig has a human
gene
 Used to make
human insulin by
inserting human
gene in bacteria

Firefly DNA inserted into tobacco plant
Transgenic Cow

A Dutch biotechnology
company called
Pharming has
genetically engineered
cows, outfitting
females with a human
gene that causes
them to express high
levels of the protein
human lactoferrin in
their milk
Transgenic Bacteria
Biotechnology
Ethical issues and
implications:
Stem Cell Research
More controversy
Genetically modified
food (sometimes
called Franken
Food)
Will it harm us?
Will it harm the
environment?
Is it the future?
3.05 Evolution
Abiogenesis –
Life can come from
non life
Examples: flies from
meat
Mice from rags
Frogs and insects
from mud
Biogenesis
Francesco Redi used
flies, meat and
screens to disprove
abiogenesis.
Biogenesis
Louis Pasteur used
specially made
flasks and broth to
prove biogenesis
Theory of Natural Selection
Charles Darwin
Naturalist on the
British Ship the
HMS Beagle
The Voyage
Galapagos
Iguanas and Tortoises
Finches and Boobies
Early earth
Hypothesis that the first organisms to
evolve were
ANAEROBIC &
HETEROTROPHIC &
PROKARYOTIC
Early Earth - Experiments
Experiment:
Sparks (lightning)
Gasses (volcanoes)
Water droplets (rain)
Heat (geothermal)
NO OXYGEN
1 week = amino
acids
Evolution of eukaryotic cells
Evolution of aerobic and
photosynthetic organisms
1.
2.
3.
Prokaryotic anaerobic heterotrophic
organisms
Prokaryotic autotrophs  started to
produce oxygen and change the
ancient atmosphere
Eventually enough oxygen was
present in the atmosphere to
promote the evolution of aerobic
organisms
Evidence for Evolution
Fossils
Biochemical
similarities
Shared
anatomical
structures
Patterns in the fossil record
What can they tell
us?
The most primitive
organisms are the
oldest.
The most advanced
organisms are the
youngest.
Fossilization
Relative Dating
Finding the age by
comparing the
fossil to the rocks
or fossils near by.
Fossilization
Absolute
Dating
Using
radioactive
isotopes to
determine
age.
Biochemical similarities
Similar Structures
Similar
embryological
development can
show close
evolutionary
relationships.
Similar Structures
Four different
mammal limbs
have the same
basic bone
structure.
Mechanisms of Evolution
Variation
(provides
material)
Geographic
Isolation
Environment
(selection
pressures)
Peppered Moth
Variation provides
material for natural
selection.
Geographic Isolation
Examples: Kaibab
squirrel (top) and
the Albert squirrel
(bottom) from the
Grand Canyon
Galapagos finches
Australia’s
marsupials
Natural Selection
Recent Examples
Resistance to Pesticides