Bio 100 – Guide 08
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Common Chromosomal Abnormalities
* Turner syndrome results from a single X
chromosome (45, X or 45, X0).
* Klinefelter syndrome, the most common male
chromosomal disease, otherwise known as 47, XXY
is caused by an extra X on sex chromosome 23.
* Edwards syndrome is caused by trisomy (three
copies) of chromosome 18.
* Down syndrome, a common chromosomal
disease, is caused by trisomy of chromosome 21.
* Patau syndrome is caused by trisomy of
chromosome 13.
Molecular & Genetic basis of Cystic Fibrosis
CF Protein creates a Cl-- permeable channel in the
outer cell membrane. Persons with Cystic Fibrosis
(OMIM219700) are typically homozygous for an
allele with a 3bp deletion (508) that removes a
phenylalanine residue from a position near a
nucleotide binding domain. CF proteins with this
defect are destroyed by the cell. In the absence of
Cl-- channels, the Cl / Na balance of the cell is
disrupted. This leads to an accumulation of mucous
in the lungs, a condition which is can be fatal.
http://www.mun.ca/biology/scarr/Cystic_Fibrosis_&_CF_Protein.html
Turner syndrome or Ullrich-Turner syndrome
encompasses several chromosomal abnormalities,
of which monosomy X is the most common. It
occurs in 1 out of every 2500 female births.[1]
Instead of the normal XX sex chromosomes for a
female, only one X chromosome is present and fully
functional. A normal female karyotype is labeled
46,XX; individuals with Turner syndrome are 45,X
(also labeled 45,X0 or less commonly X(,)) though
other genetic variants occur. In Turner syndrome,
female sexual characteristics are present but
generally underdeveloped.
http://en.wikipedia.org/wiki/Turner_syndrome
Common Chromosomal Abnormalities
Some disorders arise from loss of just a piece of one
chromosome, including
* Cri du chat (cry of the cat), from a truncated
short arm on chromosome 5. The name comes from
the babies' distinctive cry, caused by abnormal
formation of the larynx.
Chromosomal abnormalities can also occur in
cancerous cells of an otherwise genetically normal
individual; one well-documented example is the
Philadelphia chromosome, a translocation mutation
commonly associated with chronic myelogenous
leukemia and less often with acute lymphoblastic
leukemia.
http://upload.wikimedia.org/wikipedia/en/b/be/Philadelphia_transformation.jpg
Making a Personal Pedigree
For each relative, try to write down as
many of these items as possible:
• Age or date of birth (and, for all family
members who have passed on, age at
death and cause of death).
When the information is unavailable,
write down your best guess (for example,
“40’s”).
Gather
information
on Medical
Problems
• Cancer
• Heart disease
• Diabetes
• Asthma
• Mental illness
• High blood pressure
• Stroke
• Kidney disease
• Alcoholism
• Others
Note the ages at which the conditions
occurred. Did Uncle Pete have his heart
attack at age 42 or age 88?
Did your mother develop diabetes in
childhood or as an adult?
• Birth defects such as spina bifida, cleft lip,
heart defects, others.
• Learning problems, mental retardation.
• Vision loss/hearing loss at a young age
(remember to record the age it began).
• For family members with known medical
problems, jot down if they smoked, their diet
and exercise habits, and if they were
overweight. (for example, you could note that
your brother John, who had a heart attack at
age 40, weighs 300 lbs and smokes 2 packs a
day).
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Although all cancer is caused by mutations in specific
types of genes (oncogenes, tumor suppressor genes,
and DNA repair genes), not all of these mutations are
inherited. Only about 1-2% of cancers are hereditary
and cluster in families with a strong shared
susceptibility. Most people have sporadic cancer
without a positive family history of the disease.
In the vast majority of cancer cases there is no
apparent familial clustering. For most common
cancers, an individual with a first-degree relative with
the disease will have approximately twice the risk of
the general population.
PseudoIsochromatic Plate Ishihara Compatible
(PIPIC) Color Vision
Enter the number you see
http://colorvisiontesting.com/ishihara.htm
PseudoIsochromatic Plate Ishihara Compatible
(PIPIC) Color Vision
Enter the number you see
http://colorvisiontesting.com/ishihara.htm
Cystic Fibrosis Carrier Rates
Race/Ethnicity
European
Caucasian
Ashkenazi Jewish
Chance of being a carrier
1 in 29
Chance both partners are carriers
1 in 841
Hispanic
American
1 in 46
1 in 2,116
African American
1 in 65
1 in 4,225
Asian American
1 in 90
1 in 8,100
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http://www.mun.ca/biology/scarr/MGA1-3-27_CF_smc.jpg
Phenylketonuria (PKU)
The defect is found
in 1 in 20,000 births,
a general screening
program (PKU Test)
has been mandated
in many states and is
routinely made
several days after the
birth of an infant.
www.elmhurst.edu/~chm/vchembook/635pku.html
The End