Transcript Gene Disorders

An
Introduction
to
GENETIC
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
disorders?
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
chromosomes.
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
DNA.
• 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
Mutations
• Insertion
– AAACACCGGG
– TTTGTGGCCC
• Deletion
– AAACCGGG
– TTTGGCCC
• Substitution
– AAACACGGG
– TTTGTGCCC
• Original DNA Code
AAACCCGGG
TTTGGGCCC
Mutagen
• A mutagen is anything that can
cause a mutation in DNA.
• Examples of mutagens include:
– Radiation
– Asbestos
– Chemicals in
cigarette smoke
– Pollution
Karotypes
• A karyotype is an organized profile of a
person's chromosomes.
• In a karyotype, chromosomes are arranged
and numbered by size, from largest to
smallest.
• 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
guides.
• http://learn.genetics.utah.edu/content/
begin/traits/karyotype/
Normal Human Karyotypes
Gene Disorders
Cystic Fibrosis
Sickle Cell Anemia
Hemophilia
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.
http://learn.genetics.utah.edu/c
ontent/disorders/whataregd/cf/i
ndex.html
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.
http://learn.genetics.utah.edu/content/di
sorders/whataregd/sicklecell/index.html
Hemophilia
• 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
bruising
Hemophilia
• 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
chromosome
• Turner Syndrome – incomplete or
missing X chromosome (girls only)
• Edward’s Syndrome – 3 copies of
the 18th chromosome
• Triploidy – 3 copies of every
chromosome
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
Dwarfism
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.
Kenadie
http://www.youtube.com/watch?v=8oJUeqQx3PM
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
chromosomes.
Triploidy
Triploidy
• 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
chromosomes.
Maddox Elise
Hodge
Triploidy is RANDOM and doesn’t
affect every pregnancy!