Human Genetic Disorder

WebquestBianca Hernandez: Disorder Specialist

Courtney Okoyeocha: ParentErike Arias: Genetic Counselor

January 29, 2014Biology Honors

Period 6

Role

Disorder Specialist

Disorders

• The disorders we chose were:• Tay-Sachs Disease• Colorblindness

• My role is the Disorder Specialist

What type of disorder is it- gene or chromosomal?• Tay-Sachs Disease

• caused by genetic mutation in the HEXA (hexosaminidase A) gene - karyotype• HEXA is critical in the brain and spinal cord• enzyme found in lysosomes, which are the structures in

cells that break down toxic materials and act as a recycling center

• recessive gene disorder

• chromosome 15 • mutation reduces/eliminates the activity of the enzyme

HEXA, which prevents the enzyme from breaking down GM2 (ganglioside), which begins to accumulate abnormally in cells, builds up toxins, predominantly in nerve cells in the brain and spinal cord. • all this leads to the symptoms of Tay-Sachs Disease

Cont.

• picture of the molecular location of chromosome 15

What are the signs and symptoms of the disorder?• 3-6 months

• muscle weakness• an increased startle response• Sudden contractions of large muscle when falling

asleep

• 6-10 months• lose ability to perform tasks, ex. sitting• decreased eye movement/contact & attentiveness

• After 8-10 months• move less & less responsive • vision lose & seizures

Cont.• 2-4 years old

• trouble swallowing• progress into an unresponsive vegetative state• Usually death from pneumonia - inflammation of

lungs

What different tests could have been provided to

the parent to have found out about the disorder

before its birth?• Prenatal Testing• unborn babies could have been tested for the

HEXA

• Parents could have had a simple blood test to see if they are both carriers, allowing them to refer to a genetic counselor

What other names or abbreviations are used for the

disorder?• B variant GM2 gangliosidosis

• GM2 gangliosidosis, type 1

• HexA deficiency

• Hexosaminidase A deficiency

• TSD

What type of disorder is it- gene or chromosomal?

• Colorblindness• inherited sex-linked recessive disorder• 23 chromosome• Others include X Chromosome, chromosome 7 chromosome 2, and

chromosome 8

• 8-10% in men are affected

• Less than ½ of 1% in women affected

• Mutations in the red and green light-sensitive proteins located on the X Chromosome can cause colorblindness

• There are 3 categories• red-green color vision defects (most common)• blue-yellow color vision defects • complete absence of color vision – achromatopsia (severely

affected, rare)

What are the signs and symptoms of the

disorder?• Not being able to distinguish• different shades of red and green• different shades of blue and yellow• any colors

• ex. makes it hard to see the different colors of the rainbow and the color of the sky at sunrise and sunset

• ex. not being able to tell the difference between the traffic light colors

What different tests could have been provided to

the parent to have found out about the disorder

before its birth?• doctors use a simple eye chart w/ colors implanted in the patterned shapes

Quick Test

• Ex.1

Cont.• Ex.2

Cont.

• Ex.1 = 2

• Ex.2 = 74• some with colorblindness may read 21

or not see anything at all

What other names or abbreviations are used for the

disorder?• Colorblindness

• Color Vision Deficiency

• Color Vision Defects

Role

Parent

What kind of lifestyle your

child will have with this

disorder?• My child won’t have a lifestyle if the

form is infantile. If my child got the disorder later in, which is rare, my child would live a careful lifestyle.

How long your child will live?

• If my child got the disorder when he/she was an infant she will live about 4 to 5 years.

• But if my child got the disorder late around the mid-30s it depends on how severe the symptoms are

If your child with the disorder

will be able to have children of

his/her own?• No my child would not live long

enough if gotten as an infant.

• Yes if my child live long enough.

If child will be affected?

• There is a 25% chance that the child will be affected.

If you were to have more children, what

is the probability that the child will be

affected?• My child will have a 25% chance of

being affected.

What kind of lifestyle your

child will have with this

disorder?Colorblindness:

• My child will live a challenging lifestyle. It will a little challenging when learning some things.

How long your child will live?

• My child will live as long as he/she can. It will not affect his/her life spine.

If your child with the disorder

will be able to have children of

his/her own?• Yes my child can have his/her own

child

If child will be affected?

• My child will have a 50% chance of being affected.

If you were to have more children, what

is the probability that the child will be

affected?• My child will have a 50% chance of

being affected if one parent is also.

Sites – Tay-Sachs• http://ghr.nlm.nih.gov/condition/tay-sachs-

disease

• http://rarediseases.info.nih.gov/gard/7737/resources/resources/1

• http://my.clevelandclinic.org/childrens-hospital/health-info/diseases-conditions/neurological-conditions/hic-tay-sachs.aspx

• http://ghr.nlm.nih.gov/gene/HEXA

• http://kidshealth.org/parent/medical/genetic/tay_sachs.html#

Sites - Colorblindness

• http://www.colourblindawareness.org/colour-blindness/inherited-colour-vision-deficiency/

• http://ghr.nlm.nih.gov/condition/color-vision-deficiency

• http://www.dnalc.org/view/15940-What-is-color-blindness-.html

• http://www.mayoclinic.org/diseases-conditions/poor-color-vision/basics/symptoms/con-20022091