Tutorial 9 - six affected persons have the 3 and the 2 kb...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Biology 2CO3 Genetics March 14th-18 th , 2011 Tutorial #9: Molecular markers. DNA studies are performed on a large family that shows a certain autosomal dominant disease of late onset (approximately 40 years of age), which involves gene D . A DNA sample from each family member is digested with the restriction enzyme TaqI and subjected to gel electrophoresis. A Southern blot is then performed, with the use of a radioactive probe consisting of a part of human DNA cloned in a bacterial plasmid. The autoradiogram, aligned with the family pedigree, is a follows. Affected members are shown in black. a. Analyze fully the relation between the DNA variation, the probe DNA, and the gene for the disease. Draw the relevant chromosome regions. b. How do you explain the last son? c. Of what use would these results be in counseling people in this family who subsequently married?
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Solution a. The probe detects three bands of 5, 3, and 2 kb. All family members have the 5 kb band. Five of the
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: six affected persons have the 3 and the 2 kb bands, but no unaffected person have them; therefore these fragments are likely to be linked to the disease allele (in cis arrangement). Because 3 plus 2 adds up to 5, a likely arrangement in the father is as follows, where D is the disease allele and an arrowhead represents the restriction-enzyme target site: The mother is as follows: b. The last son most likely represents a crossover between the disease locus and the RFLP (restriction fragment length polymorphism) locus, resulting in a chromosome with D and the 5 kb fragment. c. Because the 3 and 2 kb fragments are linked to the disease allele, the presence of these fragments can be used as a predictor for the disease. However, the diagnosis has to take into account the possibility of a crossover....
View Full Document

This note was uploaded on 06/09/2011 for the course BIOLOGY 2c03 taught by Professor Dej during the Spring '11 term at McMaster University.

Page1 / 2

Tutorial 9 - six affected persons have the 3 and the 2 kb...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online