Genetic Research Paper

clattergumneckΒιοτεχνολογία

23 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

64 εμφανίσεις








TJ Hensel

October 29, 2009

Genetics

Genetic Disorder Research Paper

Bloom Syndrome






A genetic disorder can be a simple disorder that is not noticeable in
some, but can be extremely dangerous and even lethal in others. There are
thousands of gene
tic disorders in humans all over the world. Some genetic
disorders are common where others are extremely rare.
Whatever be their
prevalence, what is most incommodious about these disorders is that
scientists are still trying to find cures for these disorde
rs. While some
headway has been made in the direction, a lot more research is required.
Genetic disorders are highly common, but what the genetic disorder is can
quite possibly be very scarce. Genetic disorders can happen in any body, but
typically is inhe
rited but can sometimes occur in different instances. There
are several causes to a genetic disorder to occurring, but most cures are still
undetected.


A genetic disorder that can have several effects on a person that may
not happen on another is Bloom Sy
ndrome. Bloom Syndrome is a genetic
disorder in which can affect numerous amounts of people in several different
ways (Genetic Disorders in Humans). “There are many symptoms and side
affects, but there is no known cure for this genetic disorder. This disea
se is
more common in Ashkenazi Jews with a frequency of 1/100 individuals
suffering from this disorder” (Genetic Disorders in Humans). “
Since the
syndrome was first recognized, there have been more than 170 case reports
in the United States. While the diso
rder is extremely rare, it is most
prevalent among individuals of Eastern European Ashkenazi ancestry. About
one third of people with Bloom syndrome are of Ashkenazi Jewish descent,
and the carrier rate for Ashkenazi Jews is about one percent. Cases of Blo
om
syndrome have also been reported in other countries, including Japan”
(Bloom Syndrome).
The reactions in a male are different from a female. Men
with Bloom’s Syndrome
have been azoospermic (Sanz). Azoospermic means

lack of live spermatozoa in the semen
; classified as obstructive or
nonobstructive depending on whether cause is blockage of the tubules or
ducts” (The Free Dictionary). Women with Bloom’s Syndrome typically enter
menopause early. The mode of inheritance is
in an
autosomal recessive

manner
. “
Bloom's syndrome is diagnosed by clinical features and can be
confirmed by
chromosome

analysis. A greatly increased frequency of
sister
chromatid exchanges

(SCEs) in cells exposed to bromodeoxyuridine (BrdU)
is diagnostic; Bloom's syndrome is the only diso
rder in which such evidence
of hyper
-
recombination

is known to occur.
BLM

is the only
gene

known to be
mutated in Bloom's syndrome.
Molecular genetic testing

for the common
mutation
,
BLM
Ash
, is clinically available” (Sanz).

A symptom of bloom syndrome is

elangiectatic erythema (dilation of
blood vessels) appears as lesions on the skin or as butterfly
-
shaped patches
of reddened skin on the face and other areas exposed to the sun. The sclera
(white, protective, outer layer of the eyeball) blood vessels may
also become
dilated. Sun exposure worsens these symptoms. Newborns with Bloom
syndrome are often disinterested in feeding.” During infancy, typically a
baby cannot keep their food down and may suffer from regurgitation and
vomiting. It is very difficult fo
r them to keep the food down. “Bloom
syndrome causes decreased levels of immunoglobulin A and immunoglobulin
M, which leads to recurrent respiratory and gastrointestinal tract infections.”
Because of the chromosomal instability, patients have a higher risk

of
becoming diagnosed with cancer. “Bloom syndrome patients are 150 to 300
times more likely to develop cancer compared to the general population.
About 20% of Bloom syndrome patients develop malignancies. The cancers
usually arise early in life, as indiv
iduals may be first diagnosed with cancer
when they are about 25 years old.” The first physical symptom that usually
appears is a delay in growth, which occurs during prenatal onset and
throughout the rest of life. “More than 50% of children with Bloom syn
drome
are significantly underdeveloped in physical stature until they are eight years
old. Adults with Bloom syndrome have short stature. Bloom syndrome
patients typically have long limbs, disproportionately large hands and feet
and progressive contracture

of hands and feet. Upper extremities are long in
proportion to body length. Individuals with Bloom syndrome usually have a
high
-
pitched voice, a long narrow face, small lower jaw and prominent nose
and ears. Cheilitis (dry, cracked lips) with crusting or
bleeding may also
occur. Bacterial respiratory tract infection is a common symptom of Bloom
syndrome. If untreated, respiratory tract infections may progress to chronic
bronchiectasis (chronic dilatation of the bronchi). Chronic pulmonary disease
is the se
cond most common cause of death in Bloom's syndrome. Patients
have primary hypogonadism (underactive sex organs). Women with the
disorder usually experience menopause earlier than unaffected women.
Other symptoms may include learning disabilities, mental
retardation and
diabetes” (Bloom Syndrome). Typically a persons voice is much higher
pitched due to the small size of the larynx. There are several symptoms as
to what happens when bloom syndrome is occurring in a person’s body. A
person can have many of t
hese symptoms, all, or just a select few. It is all
according to the extent of the genetic disorder and how serious it really is.

There is no known treatment but a few ways to help prevent
cutaneous symptoms are to stay out of the sun and to wear sunscreen

when
going into the sun. Patients should also avoid exposure to mutagens, which
include x
-
rays, ultra violet rays, and other chemicals. “Growth hormone
therapy has been used unsuccessfully to increase height in children with
Bloom's syndrome. Also, there
is some concern that the use of growth
hormone may increase the risk for cancer later in life
” (Bloom Syndrome).
Bloom syndrome is a genetic disorder therefore there is no way to prevent
it, but you can diagnose at the prenatal state using
amniocentesis
. I
n the
near future, DNA analysis is expected to be available for Bloom Syndrome.
Recently the gene, located on chromosome 15, was able to be isolated.
Screening for Bloom’s syndrome is available because of this finding and
hopefully in the future a cure wil
l be found.

Though Bloom Syndrome can be very minor and a minute genetic
disorder, it can also be extremely dangerous. Since 1954, when the disorder
was discovered, over 170 people have been diagnosed as affected by this
disorder. The average age of death

is 27, which is typically caused by
cancer. (Lisa Katz). There are many symptoms of Bloom Syndrome and
typically if one is found, others may be prevalent later on in life. Bloom’s
Syndrome is inherited through an autosomal recessive pattern. This means
tw
o copies of the gene are altered. The gene is located on chromosome 15
and typically affects
Ashkenazi Jews. There is no treatment to this disease
but only ways to prevent the disorder from getting worse. Bloom’s
Syndrome is a very serious genetic disorder

that can be lethal and
precautions should be taken adequately. Because there is no known cure,
patients diagnosed with this disorder have a high chance of getting worse
symptoms and the possibility of developing cancerous tumors.







Table 1.
Molecular Genetic
Testing

Used in Bloom's
Syndrome

Parental
Ancestry
1

Number
of
Probands

2

Number of
Probands
/Total Number of
Probands

of that Parental Ancestry by
Genotype

3

Test
Availability
4


BLM
Ash
/
BL
M
Ash

BLM
Ash
/
insT2407

BLM
Ash
/+

+/+

+/



/


Clinical
4

and
Research

A/A

28

26/28

2/28

0

0

0

0

A/J

2

1/2

0

1/2

0

0

0

A/N

5

0

0

5/5

0

0

0

J/J

1

0

0

0

0

0

1/1

N/N

101

3/101
5

0

2/101
5

79/101

8/101

9/101

A =
Ashkenazi Jewish


J = Jewish, not Ashkenazi

N = Non
-
Jewish

A/A = Both parents are
Ashkenazi
Jewish
.

A/J = One parent is
Ashkenazi Jewish

and
one parent is Jewish but not Ashkenazi.

A/N = One parent is
Ashkenazi Jewish

and one parent is non
-
Jewish.

J/J = Both parents are Jewish, but not
Ashkenaz
i.

N/N = Both parents are non
-
Jewish.

+ =
Sequence alteration

other than
BLM
Ash

and insT2407



= No
sequence alteration

identified

1.

The parental ancestries of persons
with Bloom's syndrome and known
Bloom's syndrome
-
causing
mutations

in
BLM

[Bloom's
Syndrome Registry].
Between 25% and 33% have Jewish
ancestry; i.e. parents are A/A, A/J, A/N,
or J/J.

2.

The number of
probands

comprising
the parental ancestry group

3.

Technical limitation is probably the
explanation for failure to detect one or
neither
of the Bloom's syndrome
-
causing
mutations

in
BLM

in 18 persons studied.

4.

Targeted mutation analysis

for
BLM
Ash

is the only test that is clinically available.

5.

Those in the N/N parental ancestry
group who are homozygous or
compound
heterozygotes

for
BL
M
Ash

are from one
particular geographic area that once was
part of Spain's Nuevo Mundo (Central
America, Mexico, and the Southwest
United States) [Ellis et al 1998].










Works Cited

"Blood syndrome
-

Search."
Google
. Web. 06 Nov. 2009.
<http://www.g
oogle.com/search?hl=en&safe=active&q=blood+syndro
me&aq=f&oq=&aqi=g1g
-
m7>.

"Bloom syndrome."
Wellness.com
-

The Healthy Living Community
. Web. 06
Nov. 2009. <http://www.wellness.com/reference/allergies/bloom
-
syndrome/symptoms
-
and
-
causes>.

"Genetic Disorders

in Humans."
Buzzle Web Portal: Intelligent Life on the
Web
. Web. 06 Nov. 2009. <http://www.buzzle.com/articles/genetic
-
disorders
-
in
-
humans.html>.

Katz, Lisa. "Bloom's Syndrome."
About Judaism
. Web. 06 Nov. 2009.
<http://judaism.about.com/od/health/p/bloom
.htm>.

Sanz, Maureen M., and James German. "Bloom's Syndrome
--

GeneReviews
--

NCBI Bookshelf."
National Center for Biotechnology Information
.
Web. 06 Nov. 2009.
<http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=blo
om>.