ANSC 221 (Exam3): G5-Extension of Medellin Genetics II

What is epistasis?

A type of gene interaction where the phenotypic expression of one gene alters the expression of another gene.

What is polygenic inheritance?

An additive effect of two or more genes on a single character, resulting in continuous variation in the population.

What are multifactorial characters?

Traits that depend on multiple genes combined with environmental influences.

How does the environment impact phenotype?

Environmental factors can influence traits such as height, weight, and skin color, affecting the phenotypic range.

What is genomic imprinting?

A phenomenon where the expression of certain genes depends on which parent passed them on, often involving gene silencing.

How are organelle genes inherited?

Organelle genes are inherited maternally because the zygote's cytoplasm comes from the egg.

What is the significance of the IGF2 gene?

The IGF2 gene is required for normal prenatal growth, with only the paternal allele being expressed.

What is the role of dilution in coat color genetics?

A gene that creates a lighter coat color, requiring two copies of the dilute allele to produce the phenotype.

What is the phenotypic ratio in a dihybrid cross involving epistasis?

The phenotypic ratio can vary based on the interaction of the two genes involved.

What is an example of polygenic inheritance in humans?

Height, which is influenced by multiple genes and shows continuous variation.

How does temperature affect coat color in Siamese cats?

A temperature-sensitive enzyme determines coat color, with lower temperatures activating the enzyme and resulting in dark extremities.

What are some examples of mitochondrial diseases in humans?

Mitochondrial myopathy and Leber's hereditary optic neuropathy, which affect muscular and nervous systems.

What is the relationship between skin color and environmental factors?

Skin color can vary based on environmental influences such as sun exposure and nutrition.

What is the effect of soil acidity on hydrangea flower color?

Soil acidity affects the color of hydrangea flowers, ranging from pink in basic soil to blue-violet in acidic soil.

What is the genetic basis of coat color in Labrador retrievers?

Black coat color (B) is dominant to brown (b), and the gene for pigment deposition (E) is epistatic to the coat color gene.

What is the significance of the 'tall' allele in polygenic inheritance of height?

Each 'tall' allele contributes to one unit of tallness, with combinations of alleles resulting in varying heights.

What is the inheritance pattern of organelle genes?

Organelle genes are inherited from the mother, as the cytoplasm of the zygote comes from the egg.

What is the impact of environmental factors on phenotypic expression?

Environmental factors can alter the expression of traits, leading to variations in phenotype despite the same genotype.

What is the role of free aluminum in hydrangea flower color?

Free aluminum is necessary for producing bluer colors in hydrangea flowers, influenced by soil acidity.

Epistasis

A gene interaction where one gene masks or modifies the expression of another gene.

Dilution (Autosomal Recessive)

A trait where two recessive alleles lighten coat color, such as turning black to blue or red to fawn.

Polygenic Inheritance

A trait controlled by two or more genes, often showing continuous variation (e.g., height, skin color).

Multifactorial Traits

Traits influenced by both genetic and environmental factors (e.g., intelligence, flower color, weight).

Genomic Imprinting

A phenomenon where gene expression depends on the parent of origin due to allele silencing during gamete formation.

Organelle Genes (Extranuclear Inheritance)

Genes located in mitochondria or chloroplasts, inherited maternally through the egg cytoplasm.

Mitochondrial Myopathy

A disease caused by mitochondrial gene mutations affecting muscle function.

Leber's Hereditary Optic Neuropathy

A mitochondrial disorder causing vision loss due to ATP production defects.

E Gene (Labrador Retrievers)

Controls pigment deposition; epistatic to B gene.

B Gene (Labrador Retrievers)

Controls pigment type; black (B) is dominant to brown (b).

Hydrangea Flower Color

Influenced by soil pH and aluminum content; acidic soil leads to blue flowers, basic soil to pink.

Siamese Cat Coat Color

Determined by a temperature-sensitive enzyme; cooler areas produce dark fur.

Buckskin, Palomino, Bay, Chestnut (Horse Coat Colors)

Result from interactions among multiple genes (E, A, C) and epistatic relationships.

Quantitative Characters

Traits that vary continuously and are influenced by multiple genes (e.g., birth weight, height).

IGF2 Gene

A growth factor gene expressed only from the paternal allele; mutations affect prenatal development.