BIO220H1 : bio220mt1sg.pdf

Review the factors affecting the phenotypes of Mendelian charaters: incomplete dominance,

co-dominance, multiple alleles, pleiotropy, polygenic inheritance, environmental effect, epistasis, and epigentics with examples.

After crossing my pet black mouse, Zwart, with my pet white mouse, Blanca, eight offspring were produced. Two were, black, four were gray, and two were white. The gray offspring show an example of what type of allele interaction?

a. incomplete dominance

b. autosomal recessive

c. polygenic effects

d. X-linkage

e. environmental effects

1. Imagine hypothetically that the gender of a reptile iscontrolled by a single gene with two alleles, designated Aand a. The outcome of this trait is affected by thetemperature of the environment. When raised in a coolerenvironment, the dominant A allele confers maleness, andthe a allele confers femaleness. However, when raised in awarmer environment, the homozygote aa animal is male. If aheterozygous individual is crossed to a female reptile, what arethe proportions of offspring that are male and female when raisedin a cool environment? How do the proportions change if theoffspring are raised in a warm environment?

2. In the laboratory, a genetics student crossed flies withnormal long wings to flies with mutant short wings, which thestudent believed to be a recessive trait. In the F1 generation, allflies had long wings. In the F2 generation, the following resultswere obtained:

792 long-winged flies and 208 short-winged flies

Is this gene behaving according to standard Mendelian genetics?What do the data suggest about the short-winged mutation?