Forms of Dominance

Dominance and Expression of Genes

Unit 4 Notes

Poll

Do you remember the two different types of genes we discussed before Christmas Break?

• Yes!

• Maybe...?!

• No D:

Alleles and genes can be expressed in the following ways:

• Dominant Traits

• Recessive Traits

• Incomplete Dominance

• Codominance

When we discussed genes, we stated that they could be homozygous or heterozygous.

To have a homozygous set of alleles, that means both of the expressed genes are the same. If you were to see this as a genotype, this would look like TT or tt for example.

For a genotype to be heterozygous it would be written as Tt.

Dominant and Recessive Alleles

Dominant alleles are expressed with capitol letters, while the recessive alleles are represented by the lower-case letters.

Dominant alleles are the alleles that are portrayed, while the recessive alleles are masked.

Polygenetic Inheritance

In some cases, there could be more than two alleles for the same trait, an example of this is rabbit's fur which could be four possible colors.

Polygenetic Inheritance

This is when a trait can be controlled by two or more genes, examples of this includehair and skin tone.

Incomplete Dominance

Sometimes we experience what is called incomplete dominance. This is when neither allele from either parent is completely dominant. The phenotype of the offspring is a heterozygous mix of the parents.

An example: Red Snapdragon and White Snapdragon produce a Pink snapdragon

Codominance

The other type of trait that we can see is called codominance. This is when both genes appear equally on the offspring.

Example: A black chicken and a white chicken produce a speckled chicken.

Multiple Choice

A highly spotted wild cat and a non-spotted wild cat produced this offspring with some spots:

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

"The offspring's phenotype is an intermediate (blended) phenotype of the two parental phenotypes"

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

A woman with curly hair and a man with straight hair produced a child with wavy hair:

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

A man with blue eyes and a woman with brown eyes produced a child with brown eyes:

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

A pink flower and a white flower produced this offspring:

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

A pink flower and a white flower produced this offspring:

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

A long-haired female rabbit and a short-haired male rabbit produced this offspring with a medium-length coat:

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

A black male and white female produced this grey offspring:

• Incomplete dominance

• Codominance

• Complete dominance

Multiple Choice

A brown rooster and a white chicken produced this speckled offspring:

• Incomplete dominance

• Codominance

• Complete dominance