PRB Regulation and Retinoblastoma Concepts

The video discusses the role of PRB in cell cycle regulation, focusing on its interaction with E2F and the impact of RB1 gene mutations leading to retinoblastoma. It explains the two-hit hypothesis by Alfred Knudson, which suggests that two mutations are required for a phenotypic change, highlighting the difference between familial and sporadic retinoblastoma. The video concludes with a summary of PRB's regulatory function and the importance of understanding genetic predispositions in cancer development.

What is the primary function of the PRB protein in the cell cycle?

• To promote cell division

• To suppress uncontrolled cell growth

• To enhance DNA replication

• To initiate apoptosis

Which transcription factor is regulated by PRB and is crucial for S phase progression?

• RB1

• E2F

• CDK 4/6

• Cyclin D

How does PRB release E2F to allow cell cycle progression?

• Through dephosphorylation

• By binding to DNA

• Through phosphorylation by cyclin D and CDK 4/6

• By degrading E2F

What role do growth factors play in the regulation of PRB activity?

• They inhibit cyclin D production

• They promote PRB degradation

• They lead to cyclin D production and PRB phosphorylation

• They have no effect on PRB

What happens to the cell cycle when there is no growth factor and PRB is mutated?

• Cell cycle reverses

• Cell cycle halts

• Cell undergoes apoptosis

• Cell cycle progresses despite the absence of growth factors

What is the consequence of a non-functional PRB protein due to RB1 gene mutations?

• Increased DNA repair

• Decreased cell division

• Enhanced cell cycle regulation

• Uncontrolled cell growth leading to cancer

According to the two-hit hypothesis, how many mutations are required for a phenotypic change?

• Four

• Three

• Two

• One

What is the difference between familial and sporadic retinoblastoma?

• Familial occurs later in life

• Sporadic is more common

• Familial has an earlier onset and often affects both eyes

• Sporadic is inherited

Why is familial retinoblastoma more likely to have an early onset?

• Due to environmental factors

• Because it is not inherited

• Due to a higher likelihood of the second mutation occurring

• Because both alleles are mutated at birth

What does the two-hit hypothesis suggest about the likelihood of cancer in familial cases?

• It is less likely than sporadic cases

• It is more likely due to a predisposition

• It is equally likely as sporadic cases

• It is not related to genetic mutations