Gene Disorders

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Transcript Gene Disorders

What are genetic disorders?
A genetic disorder is an
abnormal condition that a
person inherits through genes
or chromosomes.
Do you know of any genetic
Two types of Genetic Disorders
– Gene Disorders: a genetic disorder that
only affects a single gene.
– Chromosome Disorders: a genetic
disorder that is caused by the addition
or subtraction of one or more
Cause of Genetic Disorders
• Genetic disorders are caused by
mutations, or changes in a person’s DNA.
• Mutations occur when there is a change in
the order of the bases in an organism’s
• The 3 types of mutations are:
– Deletion – when a base pair is left out
– Insertion – an extra base pair is added
– Substitution – when a incorrect base
replaces a correct base
• Insertion
• Deletion
• Substitution
• Original DNA Code
• A mutagen is anything that can
cause a mutation in DNA.
• Examples of mutagens include:
– Radiation
– Asbestos
– Chemicals in
cigarette smoke
– Pollution
• A karyotype is an organized profile of a
person's chromosomes.
• In a karyotype, chromosomes are arranged
and numbered by size, from largest to
• This arrangement helps scientists quickly
identify chromosomal alterations that may
result in a genetic disorder.
Making a Karyotype
• To make a karyotype, scientists take
a picture of someone's
chromosomes, cut them out and
match them up using size, banding
pattern and centromere position as
Normal Human Karyotypes
Gene Disorders
Cystic Fibrosis
Sickle Cell Anemia
Cystic Fibrosis
• Cystic Fibrosis is a gene disorder.
• The mutation that leads to CF is on the
recessive allele. People with CF must
inherit 2 copies.
• This gene is found on Chromosome 7.
• Symptoms: the body produces
abnormally thick mucus in the lungs and
intestines, making it hard to breathe and
digest food.
Sickle Cell Anemia
• Sickle Cell is a single gene disorder.
• The mutation that leads to sickle cell is on
the recessive allele. People with it must
inherit 2 copies.
• The mutation that causes sickle cell
affects the production of an important
protein called hemoglobin.
• Hemoglobin is the protein in red blood
cells that carry oxygen.
• People with sickle cell disease suffer from
lack of oxygen in the blood and experience
pain and weakness.
• Hemophilia is a genetic disorder in
which a person’s blood clots very
slowly or not at all.
• These people do not produce one
of the proteins needed for normal
blood clotting and could die from a
minor cut or scrap; or from internal
bleeding due to small bumps or
• Hemophilia is a sex-linked gene
disorder. This means the affected
gene is found on the X chromosome.
• The mutation that leads to hemophilia
is on the recessive allele.
– Females must inherit 2 copies of the
recessive allele to inherit hemophilia.
– Males only have to inherit 1 copy of the
recessive allele to inherit hemophilia
because they only have 1 X
chromosome. The Y chromosome does
not have the hemophilia gene.
• Normal Hemoglobin (protein)
– Glutamate (amino acid)
• Sickle Cell Hemoglobin (protein)
Valine (amino acid)
Chromosome Disorders
• Down Syndrome – 3 copies of 21st
• Turner Syndrome – incomplete or
missing X chromosome (girls only)
• Edward’s Syndrome – 3 copies of
the 18th chromosome
• Triploidy – 3 copies of every
Down Syndrome
• Down Syndrome is a chromosome
disorder in which a person’s cells
have an extra copy of chromosome
# 21.
• The extra chromosome is due to an
error in meiosis.
• People with Down Syndrome have a
distinct physical appearance and
some degree of mental retardation.
Smallest Girl in the world due to Primordial
Primordial Dwarfism
• Kenadie Jourdin-Bromley weighed 2 lbs., 8 ounces when
she was born in February 2003. She was not expected to
live more than a day, but she has survived.
She continued to defy doctors expectations and at the
age of 8 months, Kenadie was finally diagnosed with
primordial dwarfism, a genetic condition that is believed
to affect only about 100 people in the world. She stands
33 inches tall and weighs 17 pounds, roughly the size of
an 18-month-old toddler. Kenadie is 7.
Maddox Elise and Triploidy
• Mrs. Hodge’s daughter Maddox
Elise (Maddie) was diagnosed with
Triploidy on December 31, 2008.
• Maddie had a total of 69
chromosomes in each cell.
• She had a full extra set of
• Triploidy is a rare fatal genetic
disorder that only happens in
approximately 1% of pregnancies.
• Most babies diagnosed with
Triploidy are not born alive.
• Triploidy can happen from an extra
set of maternal OR paternal
Maddox Elise
Triploidy is RANDOM and doesn’t
affect every pregnancy!