Unit 4A: Genetic Pre Test

An allele whose trait always shows up in the organism when the allele is present.

• recessive allele
• dominant allele
• hidden allele
• present allele

An allele whose trait only shows up when no dominant allele is present.

• hidden allele
• dominant allele
• recessive allele
• present allele

What is a phenotype?

• The expression of a trait; physical appearance.
• refers to the genetic makeup of an individual
• An organism that has the same genes for a trait (ex. TT or tt)
• the passing of traits from parent to offspring

Which of the following alleles is homozygous recessive?

• Tt
• tt
• TT
• T

Two brown eyed parents (Bb) have a baby. What is the chance the baby is blue eyed?

• 0 %
• 25%
• 50%
• 75%

What is the genotypic ratio in this cross?
R= round r= wrinkled

• 3:1 (3 round to 1 wrinkled)
• 1:2:1 (1 RR, 2 Rr, 1 rr)
• 75% round, 25% wrinkled
• 1:3 (1 round to 3 wrinkled)

This type of inheritance pattern shows BOTH traits in hybrid offspring

• complete dominance
• incomplete dominance
• co-dominance
• dominant pattern

This type of inheritance pattern is a MIXTURE of both traits.

• incomplete dominance
• co-dominance
• complete dominance
• recessive pattern

Incomplete dominant traits results in the blending of traits. Think of red paint mixed with white paint to produce pink paint. The inheritance of flower color in snapdragons is an example of incomplete dominance.

Complete the cross between a Red snapdragon and aPink snapdragon.

What percent of the offspring would be pink?

• A. 25%

• B. 50%

• C. 75%

• D. 100%

A husband is homozygous for A-type blood and his wife is heterozygous for B-type blood, they are expecting their first child, what are the probabilities for the blood types of their child?

• A. 25% BB,

  50% AO,

  25% BO

  25% OO

• B. 25% BO,

  75% AO,

  0 % BB

  0% AA

• C. 25% AB

  25% AA

  25% BB

  25% BO

• D. 50% AB

  50% BO

  0% BB

  0% AA

Answer explanation

Remember Type O is recessive to types A and B.