Biology 205 Extensions of Mendelian Genetics
Genetics Home Page, Previous Page,
1. Multiple alleles
- Define what is meant by multiple alleles
- Discuss and solve multiple allele inheritance problems
- ABO blood system, Drosophila eye color.
2. Gene interactions and modified genetic ratios
- Discuss and solve problems related to general gene interactions e.g. comb
shape in chickens
- Define epistasis and be able to solve problems concerning epistasis.
- Explain how epistasis can arise from a metabolic point of view.
- Discuss and solve problems related to epistasis:
- Coat color in rodents
- Flower color in sweet peas - explain how the 9 - 7 ratio comes about for
the F2's. See figures 4.7 and 4.8
4. Essential genes and lethal alleles
- Define essential gene and lethal allele
- Solve problems related to lethal alleles
- Yellow body color in mice. See p 87
- Tay-sacs. See p 87- Tay sacs is a recessive lethal
- Hemophilia - X linked lethal at least when not treated!
- Note that the yellow coat color allele in rodents is an example of an allele
that is dominant with respect to coat color but it is a recessive lethal.
5. Gene expression and environmental effects
- Distinguish between penetrance and expressivity p 88
- Penetrance - for a certain dominant or recessvie gene - frequency of the
gene's expression in individuals having that allele
- example for individuals who are Aa, if the dominant allele is expressed
100% of the time, it has complete penetrance. If the dominant allele is
expressed 80% of the time it has only 80% penetrance
- Expressivity refers to a situation where individuals of a known genotype
express a range of phenotypes.
- Distinguish between sex linked traits, sex limited traits and sex influenced
- Give examples of the effects of the following on gene expression:
- Temperature - expression of an allele may be temperature sensitive:
Melanin deposition in fur of Siamese cat. p 90
There are also temperature sensitive polymerases in bacteria
- Chemicals - example in text is PKU
- Define norm of reaction
- - range of phenotypes a particular genotype can produce
- -give examples of a single genotypes producing multiple phenotypes
pgd Created 09/15/03 revised 02/13/05
Problems page 95-98:
4.1, 4.4, 4.5, 4.7, 4.14, 4.15, 4.16, 4,21, 4.26(See 4.25 for details first),
4.30. (See 4.29 first)