Morgan's Genetic Experiments

The lecture discusses Morgan's two-factor cross experiment using fruit flies to study genetic linkage. Morgan observed that certain genes did not assort independently, leading to the concept of linkage. The chromosome theory of linkage was proposed, explaining that genes on the same chromosome are inherited together. The lecture also covers crossing over, which can break linkage and create new genetic combinations. Morgan's experiments demonstrated both complete and incomplete linkage, contributing significantly to our understanding of genetics.

What organism did Morgan use for his two-factor cross experiment?

• Bacteria

• Fruit flies

• Pea plants

• Mice

In Morgan's experiment, which trait is dominant in fruit flies?

• Short wings

• Black body

• Vestigial wings

• Gray body

What was the expected ratio of progenies in Morgan's test cross?

• 2:1

• 9:3:3:1

• 3:1

• 1:1:1:1

What conclusion did Morgan draw from the observation that only parental types appeared in the test cross?

• Genes are linked

• Genes are on different chromosomes

• Genes mutate frequently

• Genes assort independently

What is the relationship between the distance of genes on a chromosome and their linkage?

• No relationship

• Inversely proportional

• Equal

• Directly proportional

What is the term for the exchange of gene segments between nonsister chromatids?

• Linkage

• Crossing over

• Replication

• Mutation

What type of linkage results in only parental combinations appearing?

• Incomplete linkage

• Partial linkage

• Complete linkage

• No linkage

What percentage of recombinants did Morgan observe in his experiment?

• 17%

• 0%

• 25%

• 50%

Which scientist(s) discovered the absence of crossing over in certain organisms?

• Franklin

• Watson and Crick

• Bridges and Darlington

• Mendel

What is the significance of Morgan's two-factor cross experiment?

• It demonstrated the concept of linkage

• It discovered new species

• It showed that genes are not inherited

• It proved the theory of evolution