Question

1) Select the true statements about dominant and recessive genes, assuming complete penetrance of the genotype. Circle all that apply. (1.5)

1. For an offspring to be phenotypically dominant for a trait, at least one parent will show the trait.
2. For an offspring to be phenotypically recessive for a trait, at least one parent will show the trait.
3. In incomplete dominant or codominant traits, heterozygotes will have a different phenotype than either homozygote.
4. If both parents show a recessive trait, then all their offspring will typically show the trait too.
5. If offspring show a trait that their parents don’t, it is probably recessive.
6. For a trait that has a dominant and a recessive allele, only the homozygous dominant will show the dominant phenotype.

2)  In the venomous flying pit viper of inner Outer Mongolia, a single gene pair codes for stripe color. The alleles show incomplete dominance.  Homozygotes for one allele have red stripes; homozygotes for the other have blue stripes.  What would be the expected result for offspring of a homozygous red parent and a homozygous blue parent?  (.5)  (pick one)

1. All the offspring would have purple stripes.
2. Half the offspring would have red stripes and half would have blue.
3. All the offspring would have red stripes but would carry the allele for blue.
4. Offspring would have both red and blue stripes.
5. The offspring would be blue and red plaid.

3)   A lesser green-footed roadrunner is homozygous dominant for extremely attractive lime green feet but only 75% of her offspring show this stunning trait.  What does this indicate about the trait?  (.5)  (pick one)

a) The genes show conditional recessivity.                             b) The genes have low expressivity.

c) The genes show incomplete penetrance.                             d) The trait is of high heritability.

Answer 1

1) The options A and B apply that is ;

A For an offspring to be phenotypically dominant for a trait, at least one parent will show the trait

.B For an offspring to be phenotypically recessive for a trait, at least one parent will show the trait.

2) The option D applies that is ;

D fspring would have both red and blue stripes

3)The option A apply that is ;

A   The genes show conditional recessivity.