AnIntroduction

toGENETIC

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 an incorrect base

replaces a correct base

Mutations• Substitution

– AAACACGGG– TTTGTGCCC

• Deletion– AAACCGGG– TTTGGCCC

• Insertion– AAACACCGGG– TTTGTGGCCC

• Original DNA CodeAAACCCGGGTTTGGGCCC

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.

Cystic Fibrosis

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.

Sicke Cell Anemia

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

• Smallest Girl in the World

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 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!