Mechanisms of Genetics

Some angelfish colors are determined by codominance. Possible phenotypes and genotypes of angel fish are shown.

Which answer shows the expected phenotypes of offspring resulting from a cross between a black angel fish and a black-lace angel fish?

• Silver: -

  Black: 50%

  Black Lace: 50%

• Silver: 50%

  Black: 50%

  Black Lace: -

• Silver: 25%

  Black: 25%

  Black Lace: 50%

• Silver: 25%

  Black: 50%

  Black Lace: 25%

Answer explanation

Mice have two unlinked allele pairs that affect fur color. The table shows how allele pairs affect fur color. The term "agouti" describes fur with pigmentation that changes in each hair from the shaft to the tip, giving the fur a banded appearance. Mice with the aa allele pair are albino, regardless of the second allele-pair combination.

What is the probability of albinism in the offspring of a cross between two mice with AaBb alleles?

Albinism is an autosomal recessive condition. Which answer choice displays the genotype probability when an albino female mates with a male that is heterozygous for this albinism trait?

• 50% aa

  50% Aa

• 25% aa

  25% AA

  50% Aa

• 100% Aa

• 100% aa

Answer explanation

Remember:

When identifying the genotype of each parent, you simply look at the FIRST and LAST gametes identified in the foil method.

First two: RY

Last two: ry

Genotype: RrYy

A genetic cross involving two unlinked genes is represented.

AaGG X aaGg

Which genotype is NOT possible in the offspring produced by the cross?

• AaGG

• Aagg

• aaGg

• aaGG

In the early 1900s, Thomas Hunt Morgan was among the first scientists to contribute to the chromosome theory of heredity. Morgan's investigations into heredity in the fruit flies led him to propose that the event represented in the diagram sometimes occurs.

Which statement about the event represented in the diagram is valid?

• The event represents RNA translation in the smooth endoplasmic reticulum.

• The event takes place in bacterial cells.

• The event produces genetically identical daughter cells.

• The event provides genetic diversity in eukaryotic cells

Answer explanation

The picture is an illustration of Crossing Over.

Crossing over leads to genetic diversity.