GENETICSTest Review

Test Layout 16 multiple choice/matching questions 9 fill-in the blanks (terms/definitions)

4 normal dom./rec. crosses (1 is an F1 cross)

2 incomplete dominance crosses

1 extra credit cross

Important Terminology Genetics Gene Allele Dominant Recessive P, F1, & F2

generations Gamete Punnett square

Homozygous Heterozygous Law of Segregation Law of Independent

Assortment Genotype Phenotype Incomplete

Dominance Co-dominance

Types of Inheritance Patterns Dominant-recessive (use A and a)

Incomplete Dominance (use A and A’)

Co-dominance (use A and A’)

Ratios to Memorize In a dominant-recessive cross, crossing

two heterozygotes results in a 3:1 phenotype ratio.

In incomplete and co-dominant crosses, the same cross results in a 1:2:1 phenotype ratio.

Example Cross 1 In leprechauns, blue eyes (B) are

dominant over grey eyes.

Cross a male leprechaun heterozygous for eye-color with a pure-breeding (homozygous) female with blue eyes. What phenotype ratio do you expect?

Example Cross 2 In leprechauns, red hair (R) is dominant

over blonde hair.

If a blonde-haired leprechaun female mates with a male leprechaun that is heterozygous for hair color, then they have 12 little leprechaun children, how many of those children do you expect to have the same hair color as their mother?

Example Cross 3 If a pea plant that is homozygous

dominant for smooth seeds is crossed with a plant that is homozygous recessive for wrinkled seeds, what phenotype ratio do you expect in the F2 generation?

If 4000 plants are produced, is it reasonable to expect that 2,892 of them will be wrinkled?

Example Cross 4 Fruit flies express an incompletely

dominant inheritance pattern when their wings are observed. While homozygous flies can have full wings or be wingless, heterozygous flies are born with small, shriveled wings, called “vestigial” wings.

What offspring result from the cross of a full-winged fly and a vestigial-winged fly?

Example Cross 5 Fruit flies express an incompletely dominant

inheritance pattern when their wings are observed. While homozygous flies can have full wings or be wingless, heterozygous flies are born with small, shriveled wings, called “vestigial” wings.

50 full-winged fly males are crossed with 50 wingless females, then their hundreds of offspring are crossed. What phenotype ratio do you expect in the F2 generation?