Genetics: Phenotypes and Inheritance

The video tutorial covers exceptions to Mendel's rules in genetics, including incomplete dominance, co-dominance, and polygenic traits. It explains how some traits are controlled by multiple genes and how environmental factors can influence gene expression. The session provides examples to illustrate these concepts, helping students understand the complexity beyond simple dominant and recessive alleles.

What is the basic principle of Mendel's rules regarding alleles?

• Alleles are always dominant.

• One allele is inherited from each parent.

• Alleles are always recessive.

• Each parent contributes two alleles.

In incomplete dominance, what is the result when a red flower is crossed with a white flower?

• A red flower

• A white flower

• A pink flower

• A speckled flower

Which of the following best describes incomplete dominance?

• Alleles are expressed in a spectrum.

• One allele is completely dominant over the other.

• Neither allele is dominant, resulting in a blend.

• Both alleles are fully expressed.

In co-dominance, what is the phenotype of an organism with both red and white alleles?

• White

• Red and white speckled

• Red

• Pink

What is the key characteristic of co-dominance?

• Neither allele is expressed.

• Both alleles are fully expressed.

• Both alleles are partially expressed.

• One allele is dominant over the other.

What defines a polygenic trait?

• Controlled by a single gene

• Controlled by multiple genes

• Always dominant

• Always recessive

Which of the following is an example of a polygenic trait?

• Flower color

• Height

• Blood type

• Eye color

How can environmental conditions affect gene expression?

• They cannot affect gene expression.

• They can turn genes on or off.

• They make genes recessive.

• They make genes dominant.

Why might identical twins have different phenotypes?

• They have different parents.

• They inherit different alleles.

• They are exposed to different environments.

• They have different DNA.

What is the significance of environmental factors in genetics?

• They can alter gene expression.

• They have no significance.

• They determine the genotype.

• They make all genes recessive.