Genetics: Lethal and Dominant Genes

The video tutorial explores the concept of lethal genes, providing examples such as rodent fur color and albinism in plants. It discusses genetic crosses, expected phenotypic ratios, and the analysis of results indicating lethal genes. The concept of pleiotropy is introduced, where a single gene affects multiple traits. The tutorial also covers the dominance and recessiveness of genes, explaining how a gene can be dominant for one trait and recessive for another, using the example of a gene affecting both coat color and lethality.

What is a lethal gene?

• A gene that enhances survival

• A gene that causes death in individuals

• A gene that only affects plants

• A gene that has no effect

Which of the following is an example of a lethal gene in nature?

• Green fur in rodents

• Tall stature in humans

• Blue eyes in humans

• Albinism in plants

In the classic crossbreeding experiment, what was the expected phenotypic ratio?

• 1:1

• 2:1

• 4:0

• 3:1

What was the observed phenotypic ratio in the crossbreeding experiment?

• 2:1

• 1:1

• 4:0

• 3:1

What is pleiotropy?

• A gene that only affects plants

• A single gene affecting multiple characteristics

• Multiple genes affecting a single characteristic

• A gene that has no effect

What is the term for a gene that affects multiple characteristics?

• Pleiotropic gene

• Neutral gene

• Recessive gene

• Dominant gene

How does the gene responsible for coat color and lethality behave?

• Dominant for coat color, recessive for lethality

• Recessive for both traits

• Dominant for both traits

• Recessive for coat color, dominant for lethality

When is the gene responsible for lethality lethal?

• In a nullizygous state

• In a hemizygous state

• In a heterozygous state

• In a homozygous state

What is a dominant gene?

• A gene that only expresses in a homozygous state

• A gene that expresses its trait in a heterozygous state

• A gene that has no effect

• A gene that only affects plants

What is a recessive gene?

• A gene that has no effect

• A gene that expresses its trait in a heterozygous state

• A gene that expresses its trait only in a homozygous state

• A gene that only affects plants