Genetics Case Study: What’s wrong with this patient?
Task: work through this case step-by-step, using your book if you need to.
Each member of the group should complete notes (and answer all questions) in their lab-book.
When your group is finished with one step or sample, ask for the next sheet from your teacher.
You must eventually complete all 4 tests in Step 2 before going on to Step 3.
Step 1: The Case History
Patient: 19 year-old African-American male.
What do you want to do next?
a.
b.
c.
d.
Family history
Observe blood sample
Blood protein test
DNA sequencing
Adapted from works by Stephen Taylor, Based on “The Mystery of the Crooked Cell”
http://web.mst.edu/~djwesten/Images/Crooked_Cell.pdf
Genetics Case Study: What’s wrong with this patient?
Step 2: Family History
Create the patient’s family history using the clues in the case history and this template pedigree chart.
You will need to shade in some of the squares and circles.
What is an allele?
What do the terms recessive and dominant mean?
What type of allele do you think is causing this illness? Why?
What do you want to do next?
a.
b.
c.
d.
Family history
Observe blood sample
Blood protein test
DNA sequencing
Or: We’re done – go to step 3.
Adapted from works by Stephen Taylor, Based on “The Mystery of the Crooked Cell”
http://web.mst.edu/~djwesten/Images/Crooked_Cell.pdf
Genetics Case Study: What’s wrong with this patient?
Step 2: Blood sample
The slides below are light-micrographs of erythrocytes from a healthy person and from the patient.
How wide is a normal erythrocyte?
Calculate the magnification of these images.
Describe how the patient’s erythrocytes differ from a healthy person’s.
Based on this, can you explain why the patient felt some of his symptoms?
What do you want to do next?
a. Family history
b. Observe blood sample
c. Blood protein test d. DNA sequencing
Or: We’re done – go to step 3.
Adapted from works by Stephen Taylor, Based on “The Mystery of the Crooked Cell”
http://web.mst.edu/~djwesten/Images/Crooked_Cell.pdf
Genetics Case Study: What’s wrong with this patient?
Step 2: Blood protein test
The images below represent the 3D structures of hemoglobin in a healthy person and in the patient.
What differences do you see in the structures of these hemoglobin molecules?
How might this lead to differences in erythrocyte cell shape?
What level of protein structure is shown here?
What determines the structure of a protein and why would these be so different?
What do you want to do next?
a.
b.
c.
d.
Family history
Observe blood sample
Blood protein test
DNA sequencing
Or: We’re done – go to step 3.
Adapted from works by Stephen Taylor, Based on “The Mystery of the Crooked Cell”
http://web.mst.edu/~djwesten/Images/Crooked_Cell.pdf
Genetics Case Study: What’s wrong with this patient?
Step 2: DNA Sequencing
The gene for Hb production is called HBB and is found on chromosome 11 at locus 11p15.5. The gene of
the patient was sequenced and compared to that of a healthy sample. Transcribe and translate this
section of the gene. You do not need to look for the start codon.
Don’t forget – we transcribe the antisense strand!
Define gene locus.
What change has occurred in the base sequence of the DNA?
What amino acid has been replaced in the patient? Use a genetic code chart to help you.
Search for structural diagrams of the images of these amino acids – draw them.
How are the properties of the amino acids different and how might this affect the final structure of the
hemoglobin molecule?
What do you want to do next?
a.
b.
c.
d.
Family history
Observe blood sample
Blood protein test
DNA sequencing
Or: We’re done – go to step 3.
Adapted from works by Stephen Taylor, Based on “The Mystery of the Crooked Cell”
http://web.mst.edu/~djwesten/Images/Crooked_Cell.pdf
Genetics Case Study: What’s wrong with this patient?
Step 3: The Diagnosis
Now you have the patient’s history and lab tests, it’s time to put the data together to make a diagnosis.
We think the patient is suffering from:
Because:
Confirmation: search for the gene and location in the NCBI’s gene database:
http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene
What is the name of this mystery disorder?
Try searching the names of three other genetic diseases that you know of.
Where are they located and what causes the illness?
Genetic disorder
Location (gene locus and name)
Effects of mutation
Phenylketonuria (PKU)
Consolidation:
Use the class presentation and worksheets to complete notes on the section chromosomes,
genes, alleles and mutations. Read ahead and get an idea for the subject of Genetics.
Adapted from works by Stephen Taylor, Based on “The Mystery of the Crooked Cell”
http://web.mst.edu/~djwesten/Images/Crooked_Cell.pdf