Genetic Disorders – Chromosome Disorders

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					 Genetic Disorders –
Chromosome Disorders
What are chromosome disorders?
Chromsome – Large
package of DNA
which contains
1000’s of genes

Disorder– Extra or
missing chromosome
OR large piece is
missing or extra
     What types of chromosome
       disorders are there?
Monosomy - Missing
Trisomy - Extra
Deletion – Piece of
chromosome is missing.
Addition – Piece of
chromosome is extra.
   How common are chromosome disorders?
" Chromosomal abnormalities occur in about 1 of 200 live

"Approximately 15 percent of all recognized pregnancies in
human beings terminate in spontaneous abortion, and in
about half of all spontaneous abortions, the fetus has a
major chromosome abnormality."
   How do chromosome disorders occur?

1. non-disjunction
during meiosis

2. More likely
to occur later in
         Autosomal Disorders
Autosome – Any chromosome that isn’t
X or Y

Chromosome affected
Trisomy 21
           Autosomal Disorders
Symptoms –

- Learning disabilities
- heart abnormalities
- flatter head
- larger tongue
- broad hands and
short fingers
              Down Syndrome

Age of onset - birth
How is it diagnosed - Karyotype
How common is it – 1 in every 800
Life expectancy – In 1929, children
with Down Syndrome lived 9 years.
Today, people with Down Syndrome live
to age 50 and beyond.
                  Down Syndrome
Treatments/cures? – The life experience of
people with Down's syndrome varies widely. Some
children attend special schools, while others
attend mainstream schools. Some adults live
independently and find paid work. Others require
support from family, and may attend day centers
for people with learning difficulties.

        Video - What is it like to have it?
      Sex Chromosome Disorders
Sex Chromosome –X or Y

Turners Syndrome

affected Monosomy
of X or Y
Only known human
monosomy! Lost X is
generally father’s.
           Turner’s Syndrome
Symptoms –

- short
- Webbing of neck
- high, arched
fingernails and toes
- sterile
- Heart problems
            Turner’s Syndrome

Age of onset - birth
How is it diagnosed - Karyotype
How common is it –   1 out of every 2500 female births
                     Approximately 60,000 girls in U.S.
                     800 new cases each year
Life expectancy – Normal.
             Turner’s Syndrome
Treatments/cures? – Growth hormone can be
used to help with growth but the results of this
are variable and depend on many factors such as
the age at which the treatment was started.
Estrogen therapy can be given to promote
puberty. In adulthood, assisted conception may
be available to overcome fertility problems.