Non-Mendelian Genetics

Non-Mendelian traits

​

​Non-Mendelian Traits

​Non-Mendelian traits are traits that don't follow the basic rules of dominance and recessiveness that you have learned about so far. This includes:

​

​Multiple alleles

​Incomplete dominance

​Co-dominance

​Polygenic traits

​Epistasis

Video Sections

When the video preview screen appears, click on the image to play the video.

Multiple Choice

Traits that break the rules by having no clearly dominant allele are

• Non-Mendelian

• Non-Newtonian

• non-hereditary

Incomplete dominance

Incomplete dominance leads to an "in between" phenotype.

​

​Think of incomplete dominance as two phenotypes meeting each other in the middle; a compromise.

Incomplete Dominance

In this class, we will use all capital letters to indicate incompletely dominant alleles.

​

In this example, the red is incompletely dominant over white, so flowers with genotype RW have the phenotype pink.

Multiple Choice

Pink color in snapdragon flowers are a result of

• incomplete dominance of red and white alleles

• a missing allele

• codominance of pink and red alleles

Codominance

• ​Think of codominance as two alleles sharing space; both phenotypes are partially seen.

• In our class we will indicate codominance by using capital letters for all traits, for example, codominant red and white color will be written RW

• Roan color in animals such as horses and cows is a result of codominance of red and white

Roan color

This cow has genotype RW because she has a red gene and a white gene, and the alleles are codominant.

Roan color

This horse has genotype RW because it has a red gene and a white gene, and the alleles are codominant.

Multiple Choice

When two traits are equally dominant, we call this

• incomplete dominance

• independent dominance

• codominance

Example: Skin tone is a polygenic trait.

At least 150 genes contribute to skin tone. Scientists are still studying this.

​

​Polygenic: 2 or more genes contribute to a trait.

Multiple Choice

A trait determined by many genes is

• photogenic

• polygenic

Multiple Select

Human traits that are polygenic include (check all that apply)

• a cleft chin

• height

• skin tone

• widow's peak hairline

Examples: Scientists are still researching the genetics of diabetes in humans. It is believed that at least 4 chromosomes have genes for diabetes.

-

Note: Environmental factors can also affect diabetes (and other genetic conditions.)

​

​Epistasis: When 2 or more genes interact and a trait is suppressed.

Multiple Choice

Epistasis is when

• an organism is missing a gene

• an organism has extra genes

• one gene depends on another gene to be expressed

Multiple Choice

In a species of goat, white and brown are codominant. One parent is solid white and the other parent is solid brown. What is the predicted phenotype of their offspring? Sketch a Punnett square to find the answer.

• 25% white, 25% brown, 50% white & brown

• 50% white, 50% brown

• 100% white & brown

Multiple Alleles: Blood types

• Non-mendelian inheritance

• more than two alleles are available for a trait

• Human blood types are an example

In human blood types there are 3 alleles (instead of 2) that could be inherited:

• Allele A

• Allele B

  • A and B are CODOMINANT

• Allele O

  • O is recessive to both A & B

​Blood Type Alleles:

Blood type genotypes can be written with scientific notation/superscripts or with just the letters "A", "B", "AB", or "O"

Be sure to write these on your note page!

​

​Blood Type Genotypes:

Match

Match the following

• I^AI^{A or} I^Ai

• ii or I^oI^o

• I^AI^B

• I^BI^B or I^Bi

Type A

Type O

Type AB

Type B

• Type A

• Type O

• Type AB

• Type B

​Universal Donor

• Can donate to all types

• can only receive from type O

Type O

​Universal Receiver

• Can receive blood from all types

​​Type AB

Open Ended

Lisa is type A and has a baby, FuFu, that is type O. Mark is Type B and David is Type AB and both men are claiming to be FUFU's father. Explain which one could most likely be the father of FuFu.

(Draw a punnett square on your note page and upload below to go along with your explanation)