Human Heredity
 This section explains what scientists
know about human chromosomes, as
well as the inheritance of certain human
traits and disorders.
 It also describes how scientists study the
inheritance of human traits.
Human Chromosome
 How do biologists make a karyotype?
 A karyotype is simply a picture of a person's
chromosomes in mitosis.
 The chromosomes are isolated in the WBC,
stained, and examined under the microscope.
 A picture of the chromosomes is taken through
the microscope.
 They cut out the chromosomes from the
photographs, then group them together in pairs.
Make A Karyotype
 Virtual lab:
 http://learn.genetics.utah.edu/content/chrom
osomes/karyotype/
Other Virtual Lab:
http://learn.genetics.utah.edu/content/labs/
http://www.biology.arizona.edu/human_bio/activities/karyotyping/ka
ryotyping.html
The Punnett square below shows how the
sex chromosomes segregate during meiosis.
INHERITANCE OF TRAITS:
PEDIGREES AND GENETIC
DISORDERS
Pedigree definition
 Pedigree: a family history that shows how
a trait is inherited over several generations
 Pedigrees are usually used when parents
want to know if they are carriers of a
particular disorder
Making a Pedigree
 Female
 Male
 Married Couple
 Siblings
Filled in symbols
indicate
individual is
affected with a
disorder
Example of a Pedigree
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
Brother
You
Do any disorders run in this family??
Interpreting a Pedigree
 What can you tell from a pedigree?
 Whether a family has an autosomal or sex-linked disease
or disorder
 Autosomal disorder: appears in both sexes equally
 Sex-linked disorder: allele is located only on the X or Y
chromosome. Most sex-linked genes are on the X
chromosome and are recessive
 So who would have an X-linked disorder more often, boys
or girls?
 Whether a disorder is dominant or recessive
Is this disorder 1) autosomal or
sex linked, 2) dominant or
recessive?
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
Brother
You
Sex Linked! (in this case
allele is recessive and
located on the X
chromosome)
Is this disorder 1) autosomal or
sex linked, 2) dominant or
recessive?
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
Autosomal dominant!
Brother
You
Is this disorder 1) autosomal or
sex linked, 2) dominant or
recessive?
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
Autosomal recessive!
Brother
You
Common Genetic Disorders
 Color blindness
 Sickle cell anemia
 Cystic Fibrosis
 Hemophilia
 Huntington’s Disease
For more info, go to: http://www.ncbi.nlm.nih.gov/pubmedhealth/
Color Blindness
 Deficiency to
percieve colors
 Problem with colorsensing pigments in
certain nerve cells of
the eye
 About 1 in 10 men
have some form of
color blindness.
 Sex-linked disorder
Sickle Cell Anemia
 Disorder where abnormal
hemoglobin (a protein
inside red blood cells) is
produced and warps red
blood cells
 Sickle cells deliver less
oxygen to body’s tissues
and can get stuck in small
blood vessels
 Recessive trait, tends to
be seen in people of
African or Mediterranean
descent
Cystic Fibrosis
 Recessive, autosomal disease
 Life threatening, causes thick mucus to build up in
various areas of the body (lungs, digestive tract,
etc).
 Tends to run in Caucasians, of Northern/Central
European descent
(1 in 29 Americans
carry the allele)
 Average life span in US
for people with CF is 37,
death usually caused by
lung complications
Hemophilia
 Bleeding disorder, where it takes a long time for
blood to clot (body lacks proteins involved in
clotting)
 Sex-linked
(carried on the X
chromosome)
 Treatment
involves
injection with
missing clotting
protein
Huntington’s Disease
 Autosomal, dominant
 Deterioration of brain
tissue, usually begins
between age 30 and 40.
 No cure, but have
medications to cope
with symptoms
 People usually die 15-20
years after onset of
degeneration