Date post: | 19-Dec-2015 |
Category: |
Documents |
View: | 216 times |
Download: | 2 times |
Welcome to Week 3!
Today’s Agenda:
1. Reviewing Pedigrees (Part 1)2. Practicing with Chi Square Analysis (Part 2)3. Thinking About Genetics and Agriculture in
Developing Countries4. Introduction to Chromosome Mapping (Part 3)5. Comments on Next Week (Fieldtrip!)
*Don’t forget to turn in your topic statement today!*
Pedigrees….where to begin??
• Look for a pattern in the pedigree– Is the trait present in every generation?– Is the trait inherited from one parent only?
• Some assumptions to make– In most recessive traits the parents will be unaffected and
heterozygous – In recessive traits, anyone married into a family is
considered not a carrier
What type of inheritance is this?
• Which individuals have the trait?
• What type of relationship do III-5 and III-6 have?
• Autosomal Recessive• Ex: Cystic fibrosis
Try One More: What type of inheritance is this?
• What are some of the trends that you notice?
• Autosomal Dominant• Ex: Huntington Disease
Critical Skill: Building and Interpreting Pedigrees
Let’s practice! (Part 1A)
Critical Skill: Building and Interpreting Pedigrees
Working with pedigrees is a key component to understanding genetic diseases and predicting risk.
Meet Dr. Nancy Wexler
Let’s practice! (Part 1B)
Looking Ahead to Next Week: Lifton’s Work on CAD
Practicing Chi-Square Analysis
• Work with your group on Part 2 to investigate shattering and grain color in rice. (Part 2)
Genetics in Context: Agriculture in the Developing World
Our Task:1- What role does this author suggest genetics has
in agriculture in the developing world?2- What are some of the most important
obstacles this author identifies to creating food security in developing countries?
3- What aspect of this paper did you find most interesting? Were there any terms or ideas you found difficult to understand?
Genetics in Context: Agriculture in the Developing World
Your Group Should:1- Have everyone share their interpretation of the role
of genetics and/or one of the most critical obstacles from the text.
2- Have everyone share one aspect they found new, interesting, or challenging.
3- Then, prepare a brief report out on your group’s conclusions and designate a spokesperson (Part 3).
Looking Ahead to Mapping Eukaryotic Chromosomes
Why do we need to know where genes are?
• Building complex genotypes
• Identifying its structure and function
• Deciphering evolutionary mechanisms
Linkage Mapping
Linkage Mapping
How can Morgan explain his results?How can this information be used to build maps?!
Linkage Mapping
Recombination frequencies of less than 50%
suggest linkage!
Recombination frequencies of less than 50%
suggest linkage!
Linkage: Double Crossover?!?
• Crossovers can inhibit one another through an interaction known as interference
• We can quantify interference (I) by subtracting the ratio of observed to expected frequency of double recombinants from 1.
• What does it mean if I = 0? If I = 1?
Mapping With Molecular Markers
• Molecular markers = loci of molecular heterozygosity
• Let’s us take advantage of silent variation!
Try one!
A/a * M1/M2 X a/a * M1/M1What do you expect to see? (Part 4)
Mapping With Molecular Markers
A/a * M1/M2 X a/a * M1/M1Results:
A/a * M1/M2 = 49%A/a * M2/M1 = 49%A/a * M2/M1 = 1%
Aa/a * M1/M1 = 1%
• So original cross must have been A M1/aM2 X aM1/aM1• 2% RF means 2 map units between the A/a locus and the M1/M2 locus
Mapping With Molecular Markers:
SNPS! (Single Nucleotide Polymorphisms) and SNP
Haplotypes
(What does it mean for a SNP to be in Linkage
Disequilibrium??)
Mapping With Molecular Markers:
Other useful markers include variable number tandem repeats (VNTRs),
Minisatellite Markers, and Microsatellite Markers.
Mapping With Molecular Markers:
• Chi-Square Analysis is often required to establish linkage.
• In humans, large sample sizes are rare, so we combine the results of many crosses to calculate Lod scores.
• LOD score >3 represent convincing support for a specific RF Value.
Double Crossover Complicates Linkage Mapping
Two Common Methods to Correct:
1. Mapping Function: RF = ½ (1 - e-m)
2. Perkins Formula
(these formulas aren’t critical for us!)
Final Product: Physical Maps!
Reminders for Next Week
1. CAD- Start Reading! (Pre-class assignment on Review Paper due Thursday at 2)
2. Read Chapter 4: Focus on key points we’ve identified today to help you prepare for the Quiz
3. Quiz 4- Posted by Monday at noon, due by Wednesday at noon.
4. Don’t forget to use our fabulous Discussion Room!
5. Next Week: ~1 hour Class session UW Symposium!