Download Orientamento In Rete

PROGETTO ORIENTAMENTO
IN RETE
CORSO DI
BIOLOGIA
In Inglese
Prof.ssa LONGO
UD 4
1
Law of Segregation
• Organisms inherit two copies of each
gene, one from each parent
• Organisms donate only one copy of each
gene in their gametes
• Two copies of each gene segregate, or
separate, during gamete formation
Segregation and Inheritance
Traits Studied by Mendel
Flower Color
In pea plants:
The allele for violet flower color
(B) is dominant
The allele for white flower color
(b) is recessive
Genotype vs. Phenotype
Genotype
BB
Homozygous dominant
Bb
Heterozygous
bb
Homozygous recessive
Phenotype
A Punnett
Square
CF - An
Autosomal
Recessive
Trait
Carrier mother
Punnett
Square
Carrier
father
G
g
G
g
GG
Gg
25%
50%
Gg
gg
50%
25%
Child with CF
Independent Assortment
• The inheritance pattern of one trait will
not affect the inheritance pattern of
another
• Independent assortment occurs during
meiosis
• For a single human gamete, the possible
ways chromosomes may assort is
astounding:
223 = 8,388,608 possible combinations
Dihybrid Cross
In snapdragons, tallness (T) is dominant to dwarfness(t),
while red color is due to gene (R) and white to its
corresponding allele (r). The heterozygous condition
results in pink (Rr) flower color. A dwarf pink snapdragon
is crossed with a plant homozygous for tallness and red
flowers. Give the possible genotypes and corresponding
phenotypes for all of the possible F1 generation.
Step #1: Determine Genotypes
of Parents
“A dwarf pink snapdragon is crossed with
a plant homozygous for tallness and red
flowers. “
Dwarf pink = ttRr
Homozygous tall, red = TTRR
Step #2: Determine Genotypes
of Gametes
“A dwarf pink snapdragon is crossed with
a plant homozygous for tallness and red
flowers. “
Dwarf pink = ttRr
tR
tr
tR
tr
Homozygous tall, red = TTRR
TR TR
TR TR
Step #3: Punnett Square
The Punnett square
determines the
genotypes of the
offspring
Gametes from
TALL red parent
TR TR TR TR
tR TtRRTtRRTtRRTtRR
Gametes from
dwarf pink parent
tr TtRr TtRrTtRr TtRr
tR TtRRTtRRTtRRTtRR
tr TtRrTtRr TtRrTtRr
Autosomal Recessive:
A Pedigree
Inheritance of an Autosomal
Dominant Trait
Incomplete Dominance
In snapdragons red
flower color is due to
gene (R) and white to its
corresponding allele (r).
The heterozygous (Rr)
condition results in pink
flower color. This is
referred to as
“incomplete dominance.”
Sex-Linked Traits
Traits whose alleles are located on sex
chromosomes
X-linked traits are traits whose allele
is carried on the X chromosome
Y-linked traits are traits whose allele
is carried on the Y chromosome. Most
Y-linked mutations lead to sterility, and
can not be inherited.
Color Blindness:
An X-linked
Recessive trait
Carrier mother
Punnett
Square
Unaffected
father
XC
XC
Xc
XCXc
XCXc
25%
Y
XCY
25%
25%
XcY
25%
Colorblind male
A Pedigree - Colorblindness
Hemophilia:
Another
X-linked
Recessive
trait
Carrier mother
Punnett
Square
Unaffected
father
XH
Y
XH
Xh
XHXH
XHXh
25%
25%
XHY
XhY
25%
25%
Hemophiliac male
Hemophilia in Europe’s Royalty
Blood Cell Antigens
Blood types are the result of the
presence (or absence) of antigens
(molecules) on the surface of the
individual’s red blood cells. These fall
into two groups:
 A, B, O blood type
 Rh factor
Codominance
The gene for antigen A and the gene
for antigen B are CODOMINANT.
Both traits are expressed completely
when the gene for A is inherited from
one parent and the gene for B is
inherited from the other parent.
Bloodtype antigens and
antibodies
A, B, O Inheritance
Allele from
Parent 1
Allele from
Parent 2
Child’s
genotype
Child’s
phenotype
A
A
AA
A
A
O
AO
A
A
B
AB
AB
B
A
AB
AB
B
B
BB
B
B
O
BO
B
O
O
OO
O
Rh Inheritance
Rh inheritance is independent of A, B, O
blood type.
Rh factor
Rh+
RhParent 1
Rh allele
Rh+
RhRh-
Possible genotypes
Rh+/Rh+ OR Rh+/RhRh-/RhParent 2
Child’s
Rh allele phenotype
Rh+
Rh+
Rh+
Rh+
RhRh-
Chromosomes
and DNA
DNA has 4 Bases
Four DNA Bases
Adenine
NH2
N
NH
Guanine
O
H3C
N
N
NH
NH
O
N
NH
Thymine
Cytosine
NH2
NH
N
O
N
NH2
NH
O
The Sugar
HO
OH
O
OH
Deoxyribose
The Nucleotides
A
O
HO
NH2
P
N
N
O
N
O
N
O
HO
OH
P
C
HO
P
N
O
O
OH
OH
T
O
G
O
N
O
OH
O
NH2
N
N
O
NH
O
H3C
NH
O
N
NH2
HO
P
OH
O
N
O
OH
OH
OH
O
Adenine pairs with Thymine
Hydrogen
Bonding
Guanine pairs with Cytosine
Hydrogen
Bonding
DNA
Genes and Base Pairs:
A Comparison
Genes
(estimated)
Base Pairs
Yeast
6,000
12 million
Round Worm
19,000
99 million
Mouse
40,000
3 billion
Fruit Fly
13,600
165 million
Human
40,000
3 billion
Species
(Saccharomyces cerevisiae)
(Caenorhabditis elegans)
(Mus musculus)
(Drosophila melanogaster)
(Homo sapiens)
The
“Central Dogma”
Possible Modes of DNA
Replication
Replication: 5’ to 3’ Direction ONLY
Continuous replication
on one strand
Discontinuous replication
on one strand
DNA Replication is
Catalyzed by Enzymes
DNA Polymerase Adds Complementary Bases
DNA Polymerase Sees Errors
DNA Polymerase Repairs Errors
Four RNA Bases
Adenine
NH2
N
NH
Guanine
O
N
NH
NH
N
O
N
NH
Uracil
Cytosine
NH2
NH
N
O
N
NH2
NH
O
The Sugar
HO
OH
O
OH
OH
Ribose
The Nucleotides
A
O
HO
P
O
N
N
O
N
O
HO
N
OH
N
O
O
O
O
OH
OH
O
G
O
P
N
OH
OH
HO
P
NH2
C
NH2
N
NH
O
N
O
OH
N
NH2
HO
P
OH
O
U
O
NH
N
O
OH
OH
OH
OH
OH
O
The
Central
Dogma
Transcription
Transcription is the process by
which RNA is built from a
template of DNA
Transcription
Transcription - Initiation
- RNA Polymerase
Transcription - Elongation
Transcription - Termination
Editing mRNA
Codons
in
RNA
Translation
Translation is the process by
which protein is made from an
mRNA template
Codons
Why Three Bases per Codon?
A one base code: 41 = 4 combinations
A two base code: 42 = 16 combinations
A three base code: 43 = 64 combinations
There are twenty amino acids, so a threebase code is the minimum required.
Translation: Initiation
Translation: Elongation
Translation: Termination
Antisense DNA Prevents
Translation
Definition
• A mutation is a change in an organism’s
DNA
– Silent mutations are changes that do not
result in a change to the organisms
phenotype
– Mutations that occur in germ cells (sperm,
eggs) are passed on to offspring
– Mutations in somatic (body) cells may be
harmless, or may result in disease such as
cancer
Chromosomal
Mutations
A Point Mutation Resulting in Nonsense
A Point Mutation: An Analogy
the red dog bit the tan cat
the red mog bit the tan cat
This point mutation changes the meaning,
resulting in nonsense
A Point Mutation Resulting in Missense
A Point Mutation: An Analogy
the red dog bit the tan cat
the red hog bit the tan cat
This point mutation changes the meaning,
resulting in missense
An Insertion Mutation in a Gene
An Insertion Mutation: An Analogy
the red dog bit the tan cat
the red rdo gbi tth eta nca
This insertion mutation changes the reading
frame
A Deletion Mutation in a Gene
An Deletion Mutation: An Analogy
the red dog bit the tan cat
the red ogb itt het anc at_
This deletion mutation changes the reading
frame
A Frameshift Mutation
History of Biotechnology
•
•
•
•
•
•
•
•
•
•
before 8000 BC – Collecting of seeds for replanting. Evidence that
Mesopotamian people used selective breeding (artificial selection) practices
to improve livestock.
around 7000 BC – Brewing beer, fermenting wine, baking bread with help of
yeast.
8000 BC - 3000 BC – Yogurt and cheese made with lactic-acid-producing
bacteria by various cultures.
1590 – The microscope is invented by Zacharias Janssen.
1675 – Microorganisms discovered by Anton van Leeuwenhoek.
1856 – Gregor Mendel discovered the laws of inheritance.
1862 – Louis Pasteur discovered the bacterial origin of fermentation.
1919 – Karl Ereky, a Hungarian agricultural engineer, first used the word
biotechnology.
1928 – Alexander Fleming noticed that a certain mold could stop the
duplication of bacteria, leading to the first antibiotic: penicillin.
1953 – James D. Watson and Francis Crick describe the structure of
deoxyribonucleic acid, called DNA for short.
History of Biotechnology
•
•
•
•
•
•
1972 – The DNA composition of chimpanzees and gorillas is discovered to
be 99% similar to that of humans.
1975 – Method for producing monoclonal antibody developed by Kohler and
Milstein.
1980 –
– Modern biotech is characterized by recombinant DNA technology. The
prokaryote model, E. coli, is used to produce synthetic insulin and other
medicine, in human form. (It is estimated that only 5% of diabetics were
allergic to animal insulins available before, while new evidence suggests
that type 1 diabetes mellitus is caused by an allergy to human insulin).
– A viable brewing yeast strain, Saccharomyces cerevisiae 1026, acts as
a modifier of the microflora in the rumen of cows and digestive tract of
horses).
– The United States Supreme Court, in 447 U.S. 303 (1980), rules in favor
of microbiologist Ananda Chakrabarty in the case of a USPTO request
for a first patent granted to a genetically modified living organism (GMO)
in history.
1984 – Nutrigenomics as applied science in animal nutrition.
1994 – U.S. FDA approves of the first GM food: the "Flavr Savr" tomato.
1997 – British scientists, led by Ian Wilmut, from the Roslin Institute report
History of Biotechnology
•
•
•
•
•
•
2000 – Completion of a "rough draft" of the human genome in the Human
Genome Project.
2002 – Researchers sequence the DNA of rice, the main food source for
two-thirds of the world's population. Rice is the first crop to have its genome
decoded.
2003 – GloFish, the first biotech pet, hits the North American market.
Specially bred to detect water pollutants, the fish glows red under black light
thanks to the addition of a natural bioluminescence gene.
2004 –
– November – Korean researchers treat spinal cord injury by transplanting
multipotent adult stem cells from an umbilical cord blood.
– December – A team of researchers at the University of Paris develops a
method to produce large number of red blood cells from hematopoietic
stem cells, creating an environment that mimics the conditions of bone
marrow.
2005 –
– January – Researchers at the University of Wisconsin-Madison
differentiate human blastocyst stem cells into neural stem cells, and
finally into spinal motor neuron cells.
Retrieved from "http://en.wikipedia.org/wiki/Timeline_of_biotechnology"
Modern Biotechnology
some examples
•
•
•
•
•
•
•
Recombinant DNA
Stem cell therapy
Cloning
Designer drugs
Genomics
Proteomics
Gene Therapy
What are the
potential benefits?
What are the
potential dangers?
What are the
ethical issue?
Genetically Modified Bacteria
Cloning: An Example
Cloning in Agriculture
Stem
Cells:
Another
Example
Gene Therapy