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The Human Genome
Human Chromosomes
• Karyotype- diagram showing the complete set
of chromosomes.
• A karyotype shows us 46 human chromosomes.
• 22 pairs are autosomes (main body parts)
• 1 pair are sex chromosomes
Normal Human Karyotype
Determining Sex
Females are XX, producing only X gametes.
Males are XY, producing both X & Y gametes.
Determining Sex
Chances of having a boy or girl are always 50%
Pedigrees
Method of tracking
traits within a family.
Squares = Males
Circles = Females
Colored = Trait
Pedigree Example
A circle represents
a female.
A horizontal line connecting
a male and female
represents a marriage.
A half-shaded circle
or square indicates
that a person is a
carrier of the trait.
A completely
shaded circle or
square indicates
that a person
expresses the
trait.
A square represents
a male.
A vertical line and a
bracket connect the
parents to their children.
A circle or square
that is not shaded
indicates that a
person neither
expresses the trait
nor is a carrier of
the trait.
Tay-Sachs Pedigree
• 1. How many
generations are there
in this pedigree?
• 2. Who died in
Generation 2?
• 3. How many kids
were produced from
generation 1?
Tay-Sacs Pedigree
• 4. Who got married
in generation 3?
• 5. How many kids
lived in generation 4?
It’s in the blood
Your blood cells have protein coats that
make them unique to other people’s
blood cells.
The alleles for blood types are both
multiple allelic and codominant.
Human Blood Groups
Phenotype
(Blood Type)
Antigen on
Genotype
Red Blood Cell
Safe Transfusions
To
From
Genetic Disorders
Recessive Disorders
Albinism- no pigment
Cystic Fibrosis- mucus in lungs
PKU – inability to break down phenylalanine
Tay-Sachs- breakdown of nervous system
Genetic Disorders
Dominant Allele Disorders
Huntington’s Disease- lose muscle control
& mental function
Achondroplasia- dwarfism
Genetic Disorders
Codominant Disorders
Sickle Cell Disease- abnormal shaped blood
cells causing blood clots
Sickle Cell Anemia
• Found mainly among African-Americans.
• The Hemoglobin that traps oxygen is
deformed so it can’t catch oxygen.
• Deformed cells can also clog small blood
vessels.
• Caused by a point mutation.
Cystic Fibrosis
• This is caused when 3-bases of your DNA
are deleted.
• RESULTS:
• Wrong protein is made.
• Heavy mucus forms in the lungs making it
difficult to breathe.
Cause of Cystic Fibrosis
Chromosome # 7
CFTR
gene
The most common allele
that causes cystic fibrosis is
missing 3 DNA bases. As
a result, the amino acid
phenylalanine is missing
from the CFTR protein.
Normal CFTR is a chloride
ion channel in cell
membranes. Abnormal
CFTR cannot be transported
to the cell membrane.
The cells in the person’s airways
are unable to transport chloride
ions. As a result, the airways
become clogged with a thick
mucus.
Sex linked traits
A trait controlled by an allele on the sex
chromosomes.
- most found on the X-chromosome
- males more likely to express these traits
Color Blindness
• Located on the X-chromosome (sex-linked).
• The most common form is red-green
colorblindness.
• You can’t distinguish between colors.
• More common among males.
Figure 14-13 Colorblindness
Section 14-2
Father
(normal vision)
Colorblind
Normal
vision
Male
Female
Daughter
(normal vision)
Son
(normal vision)
Daughter
(carrier)
Son
(colorblind)
Mother
(carrier)
Section 14-2
Figure 14-13 Colorblindness
Father
(normal vision)
Colorblind
Normal
vision
Male
Female
Daughter
(normal vision)
Son
(normal vision)
Daughter
(carrier)
Son
(colorblind)
Mother
(carrier)
Hemophilia
Located on the X-chromosome (sex-linked).
Protein for normal blood clotting is
missing.
Causes an inability of blood to clot.
Sex linked traits examples
If a male cardinal is red and female is brown,
which chromosome is the allele for red feathers
found?
Chromosomal Disorders
• Mutations with chromosomes.
• Mostly occur during meiosis(nondisjunction)
• Examples:
Down syndrome
Sex Chromosome Disorder.
Nondisjunction in meiosis I
Nondisjunction in meiosis II
Meiosis I
Nondisjunction
Meiosis II
Nondisjunction
Gametes
n+1
n+1
n-1
n-1
n+1
n-1
n
n
Number of chromosomes
Figure 8.21
Down’s Syndrome
• Nondisjunction leads to 3 copies of
chromosome #21.
• No clear understanding on why the extra
chromosome causes the birth defect.
Sex Chromosome Disorders
Turner’s syndrome
• Nondisjunction leads to only one X
chromosome being inherited.
• Causes females to be sterile.
Klinefelter’s syndrome
• Nondisjunction leads to an extra X
chromosme being inherited.
• Causes males to be sterile.
Determining Genetic Disorders
• Doctors look at Karyotypes