Linkage and Pedigree analysis Chapter 4

1. Linkage and map distance

A. Test crosses and map distance

1. Setting up test crosses

2. Parental and non parental genotypes

B. Estimating map distances

C. Map distance vs physical distance on chromosomes

D. Examples of map distance

E. Calculation of large map distances

1. Map distance between distant alleles is best estimated by sum of map distance for intervening loci

2. Mapping functions (brief mention)

II. Testing hypotheses in genetics. See page 59 - 60

A. Be able to use the chi square test to test simple hypotheses about single gene traits

B. Use Chi-square to test for independence between two genes

III. Pedigree analysis

A. Learn the standard Pedigree symbols. See page 66-67

B. Use pedigree analysis to distinguish between the following modes of inheritance: Not the typical pedigree patterns

• Autosomal recessive. p 79. Cystic fibrosis, sickle cell anemia
• Autosomal dominant p 85. Marfan syndrome, Huntington disease.
• X-linked dominant/ recessive p 88 hypophosphatemia(soft enamel disorder), color blindness
• Androgen insensitivity as example of X linked and sex limited trait. See page 192 for pedigree
• Y linked p 95 for known genes on Y chromosome
• Mitochodondrial inheritance. p 96. Note mode of transmission!

C. Define and distinguish between penetrance and expressivity. See page 99.

D. Genetic markers and gene mapping

D. Lod scores and linkage studies

1. Calculation of LOD scores.

2. Weakness of LOD score method.

3. Alternate methods for estimating linkage (brief mention)

IV. An alternate linkage method: Somatic Cell Hybridization. (not in text)

A. Grow human somatic cells and mouse somatic cells together wth sendi virus

B. Virus causes cell fusion

C. Human chromosomes eliminated randomly resulting in clones wit different numbers of chromosomes

D. Idea is to use human cells homozygous for a known nutritional deficiency on known chromosomes. Allows rapid screening of chromosomes.

E. Does not give order of genes.

Example: