Niches Lesson 5 Part 2

Who discovered gene interaction through chicken comb morphology?

William Bateson and Reginald Punnett in 1906.

What does the inheritance of comb morphology in chickens illustrate?

It is the first example of gene interaction.

What is comb morphology an example of?

Gene interaction.

What happens when a heterozygote produces more than 50% of the functional protein?

The normal gene is up-regulated to compensate for the defective allele’s lack of function.

What proportion of genes are estimated to be essential for survival?

About one-third (1/3) of all genes.

What is an example of a conditional lethal allele?

Developing Drosophila larvae that die at 30°C.

What is the Himalayan coat color pattern an example of?

A temperature-sensitive conditional allele.

What is the opposite of the Himalayan allele example in dairy cattle?

Brown Swiss cattle, where the opposite temperature-sensitive effect occurs.

What is the carbohydrate tree on the surface of red blood cells made of?

Three base sugars.

What enzyme adds a fourth sugar to the RBC carbohydrate tree?

Glycosyl transferase.

What does the IA allele encode?

An enzyme that adds N-acetylgalactosamine to the RBC carbohydrate tree.

What does the IB allele encode?

An enzyme that adds galactose to the RBC carbohydrate tree.

What are agglutinogens?

Blood surface proteins (antigens).

What are agglutinins?

Plasma antibodies.

What organism was used to study X-linked eye color inheritance?

Drosophila (fruit flies).

What additional allele did Morgan and Bridges find in the X-linked eye color gene of Drosophila?

The eosin allele.

What is malaria caused by?

A protozoan parasite called Plasmodium.

What are the three molecular explanations for overdominance?

1. Disease resistance 2. Homodimer formation 3. Variation in functional activity.

What are two examples of overdominance?

Sickle-cell anemia and Tay-Sachs disease.

What is the eosin allele of Drosophila an example of?

A gene dosage effect.

What are the three types of polydactyly?

Prefixal (radial), central, and postaxial (ulnar).

What disease is an example of an environmental condition affecting phenotype?

Phenylketonuria (PKU).

What is sex influence a phenomenon of?

Heterozygotes showing sex-dependent expression of alleles.