Download Ch 14 Notes - The Human Genome

Chapter 14
- The Human Genome
14-1 Human Heredity
• The children in this family have some traits that are
similar to their mother’s and some that are similar to
their father’s.
• Can you predict chin shape?
• Procedure
– Two parents with cleft chins, both heterozygous
for cleft chin (Cc), have three children with cleft
chins. The parents are sure that their fourth child
will not have a cleft chin. Draw a Punnett square
to see if this is possible.
• Determine the probability that the fourth child will
have a cleft chin. _________
Human Heredity
• Human Chromosomes
– Make us who we are.
– This is the genetic information (DNA)
which is inside the human cell.
• To look at these chromosomes, biologists,
photograph cells in mitosis.
– Mitosis is when the cell nucleus divides
and the chromosomes are easier to see.
– Biologists then take these photographs
and group them together in pairs.
– This picture of chromosomes arranged in
this way is called a karyotype
Karyotype
• The human body contains 46 chromosomes
– 23 (sperm)
– 23 (egg)
• Together this forms a diploid zygote
– 46 total chromosomes
Sex Chromosomes and
Autosomes
• Sex chromosomes
– Only 2 of the 46
– Determine if someone is male or female
– Female: XX
– Male: XY
• Autosomes
– Remaining 44 chromosomes
Human Traits
• Human traits are inherited
– Gregor Mendel
• Pedigree chart
– A pedigree shows a relationship within a
family
– A pedigree chart follows one specific trait
in a family
Cleopatra’s Pedigree Chart
Russian Royal Family Pedigree Chart
Polygenic
• Some traits are actually polygenic
– Controlled by two or more genes
• Shape of your eyes
• Shape of your ears
• Eye color
Other Trait Influences
• Environment
• Nutrition
• Exercise
• Your parents might both be 6 feet tall, but if
they don’t feed you, you are unlikely to grow
to be 6 feet tall.
Human Genes
• Our complete set of genetic information is
our genome
– 30,000 genes
• Blood Group Genes:
– Knowing a person’s blood group is critical
because using a wrong blood type could
be life threatening
– Rh
– ABO
• Are two genes that are part of your
blood type
Rh
• Rhesus Monkey”
• 2 alleles that determine blood type
– Rh+ is dominant & Rh- is recessive
• A person with 2 positive alleles is Rh+
• A person with a positive and a negative
allele is RH+
• A person with 2 negative alleles is Rh-
ABO
• There are 3 alleles that determine blood type
– IA, IB and i
• Two of these alleles are codominant and one is
recessive.
• Blood type is dependant upon what the antigens
are on the surface of the red blood cells
• Type A blood: lAlA, or IAi
• Type B blood: IBIB or IBi
• Type AB blood: IAIB
• Type O blood: ii
• Based on what you know of blood types; which
one of Mr. & Mrs. Lopez’s four kids must have
been adopted? _____________
Recessive Alleles
• Studying genetic disorders have helped us
understand how human genes work
• Many of these disorders are caused by
recessive alleles
Phenylketonuria (PKU)
• People with this disorder lack the enzyme
needed to break down Phenylalanine
• Causes:
– A build-up of phenylalanine in tissues
– Mental retardation
– Can be controlled by a special diet
– All babies in US are tested for this at birth
Tay-Sachs Disease
• Nervous system breakdown
• Infant death
Albinism
• Lack of pigment in skin, hair, and eyes
Cystic Fibrosis
• Excess mucus in
lungs, digestive tract,
and liver
• Susceptibility to
infections
• Death in early
adulthood if not
treated
Galactosemia
• Inability to digest the
sugar galactose.
• Causes mental
retardation, eye and
liver damage
Cystic Fibrosis
Dominant Alleles
• Not all genetic disorders are caused by
recessive alleles
• If you have a dominant allele for a genetic
disorder, it will be expressed even if you
also have a normal recessive allele
– Achondroplasia
– Huntington’s disease
– Hypercholesterolemia
Achondroplasia
• Dwarfism
Huntington’s Disease
• Mental deterioration and uncontrollable
movements
Hypercholesterolemia
• Excess cholesterol in blood
• Heart disease
Gene Expression
• In certain diseases, a small change in the
DNA of a single gene affects the structure of
a protein, causing a serious genetic disorder
– Cystic fibrosis
– Sickle cell anemia
Sickle Cell Anemia
• Abnormal hemoglobin produced because of
a single amino acid change in the
hemoglobin protein
• Causes the RBC’s to deform which causes
clogging in the capillaries
Sickle Cell Anemia
14-2 Human Chromosomes
Sex-Linked Genes
• Because the X and Y chromosomes
determine sex, genes located here are said
to be sex-linked genes
• More than 100 sex-linked genetic disorders
have been mapped to the X chromosome
• Males have just one X chromosome. Thus,
all X-linked alleles are expressed in males,
even if they are recessive
Sex-Linked Genes
• Genes that are found
on the X or Y
chromosome.
• More genes are found
on the X chromosome
than the Y
Colorblindness
• Three genes associated with color vision
are found on the X chromosome
• Males are more often colorblind because
they only have one X chromosome
Colorblindness Test
Colorblindness
• All X-linked
alleles are
expressed in
males even if
they are
recessive
Examples of
X-linked Recessive Disorders
• Hemophilia: blood-clotting disorder
• Duchenne Muscular Dystrophy
• Ichtyosis: scaly skin
• Norrie Disease: abnormal growth of retina
• Rett Syndrome: mental retardation
Hemophilia
Duchenne Muscular Dystrophy
X-Chromosome Inactivation
• Females have 2 X chromosomes and males
only one. What to do?
• In all female cells, one X chromosome is
randomly shut off.
• This causes some interesting problems if
one X chromosome has a mutated gene
Chromosomal Disorders
• Get too many or too few copies of a
chromosome
• Caused by non-disjunction during meiosis
• Exs. Down’s Syndrome: Trisomy 21
Turner’s Syndrome: X_
Klinefelter’s Syndrome : XXY
Down’s Syndrome
Turner Syndrome
Kleinfelter Syndrome
14-3 Human Molecular Genetics
Human DNA Analysis
• Genetic tests are now available for hundreds of
disorders.
• This can allow prospective parents to determine if
they are carrying recessive alleles for a disorder.
DNA Fingerprinting
• DNA is analyzed of by separating it into
fragments
• This reveals a series of DNA bands of various
sizes
• A pattern of bands is produced that can be
distinguished from any other individual in the
world (except for an identical twin).
• DNA samples can be obtained from blood, sperm,
and hair strands that have tissue at their base.
DNA Fingerprinting
The Human Genome Project
• The Human Genome Project was an attempt to
sequence all human DNA
• In June 2000, scientists announced that the
Human Genome was complete.
• There is open availability of nearly all its data.
• You can use the Internet to read the latest
genome data.
Gene Therapy
• Gene Therapy is the process of changing the
gene that causes a genetic disorder
• In gene therapy, an absent or faulty gene is
replaced by a normal, working gene
• This way, the body can make the correct protein
or enzyme it needs, which eliminates the cause of
the disorder
Gene Therapy
Ethical Issues
• What will happen to the human species of we
could design our bodies? What would be the
consequences?
• Society will have to develop a thoughtful and
ethical consensus of what should and should not
be done with the Human Genome.