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Study Questions
1. What two experimental innovations did Mendel use that allowed him to discovery the
laws of genetics?
2. What did Mendel conclude from his experiments?
3. Why Mendel's First Law of Genetics is called the Law of Segregation?
4. Why Mendel's Second Law of Genetics is called the Law of Independent
Assortment?
5. What type of cross would produce the following genetic ratios?
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3:1
1:1
1:2:1
9:3:3:1
1:1:1:1
2:1
6. A short-tailed mutant of mouse was discovered. Multiple crosses of this mouse to
normal mice produced 27 normal, long-talied mice and 25 short-tailed mice. A series of
crosses among short tailed mice were made and and 21 short-tailed mice and 11 longtailed mice were produced? Study these results and determine which phenotype is
dominant and explain the ratios observed with regards to the genotypes of the parents
in each cross.
7. You hypothesized that snapdragon flower color is controlled in a co-dominant
manner. You created an F1 population by crossing red and white parents. You selfed
the F1 plants and obtained the following ratio: 31 red, 66 pink, and 27 white flowered
plants. Perform an analysis of this data to determine if co-dominant gene action is the
correct hypothesis.
8. What is the difference between epistasis and pleiotropy?
9. Two corn homozygous, white-seeded corn lines were crossed and all progeny were
red-seeded. These red-seeded F1 progeny were selfed, and the population segregated
9 red-seeded :7 white-seeded. Explain these results by determining the number of
genes controlling seed coat colors and giving the genotypes of the parents.
10. How does a modifier gene influence the expression of a phenotype?
11. How are penetrance and expressivity related?
11. Rh-negative man with blood group O married with Rh-positive woman with blood
group AB. What is the probability of birth the Rh-negative children with blood group В?
12. What conclusions could you draw about parents whose offspring had phenotypes in
the following proportions?
a) 9 : 3 : 3 : 1 в) 1 : 1 : 1 : 1
13. In sweet peas the genes C and P when present together produce purple flowers.
But when either C or P alone it produces white flowers. What flower color would have
the progeny of following crosses?
b) ccPp  CcPp
c) CCPp  ccPP
d) Ccpp  ccPP
a) CCPPxccpp
14) If man brown eyes (B) are dominant over blue (b), dark hair (D) over red hair (d),
and the right handedness (R) over left handedness (r), what would be the outcome of
marriages between persons of the following genotype:
BBDdRr  BbDdRR
15. The father with blood group O and color blindness mother is normal with blood
group A, but her father had color blindness and blood group O. What is the probability
of birth the normal children with blood group A?
16. Red-green color blindness in humans is recessive and sex-linked. If a woman
heterozygous for color blindness marries a color blind man, what is the probability that
their first child will be a colorblind daughter?
17. If man brown eyes (B) are dominant over blue (b), dark hair (D) over red hair (d),
and the right handedness (R) over left handedness (r), what would be the outcome of
marriages between persons of the following genotypes:
BbDDRr  bbddrr
18. In sweet peas the genes C and P when present together produce purple flowers.
But when either C or P alone it produces white flowers. What flower color would have
the progeny of following crosses?
Ccpp  ccPP