Lecture 36 Cancer Genetics and Organelle DNA

What do all cancers have in common?

• Uncontrolled growth

• Evasion of death signals

• Immortality

• Angiogenesis

• Invasion

• metastasis

HALLMARKS OF CANCER

Why is a tumor defined as a clonal line of cells?

A tumor is called a clonal line of cells since it ORIGINATES FROM A SINGLE MUTATED CELLS whose descendants expand uncontrollably

What are the 3 classifications for a tumor?

1. Benign = tumor remains localized

2. Malignant = tumor has invaded surrounding tissue

3. Metastasis = tumor cells spread to other locations

What is Knudson’s Multistep Cancer Model? How does it explain that some people have a “predisposition” to cancer?

Knudson’s Multistep Cancer Model highlights that cancer is the result of MULTIPLE MUTATIONS

First mutations may be INHERITED

How do tumors evolve?

Tumors evolve by Clonal Evolution:

1. Rapid cell division increases rate of mutation

2. Cancer cell lines continue to accumulate mutations

3. Additional mutation increase the growth rate

4. New cell lines outcompete the old

5. Rate of mutation continues to increase

Cancer genes fall into 2 categories. What are they?

• Oncogenes

  • Stimulatory genes that cause cancer

  • mutations tend to act as dominant alleles

• Tumor-suppressor genes

  • inhibitory genes that cause cancer

  • mutations tend to act as recessive alleles

What is a proto-oncogene? How can viruses cause cancer?

A proto-onogene carries on normal cell function until mutated , ACTIVATED BY RETROVIRUSES

The viral insertion may disrupt gene function, viral recombination, viral promoter

What are Cyclin-dependent kinases and how are they related to cancer

Cyclin-dependent kinases (CDKs) are:

• enzymes that add phosphate groups to other proteins

• can activate or deactivate the protein

• Control key checkpoints (G1/S, G2/M)

• Depends on the protein cyclin

OVER EXPRESSION OF CDKs CAN CAUSE CANCER

What a long non-coding RNAs and how were they discovered?

Long non-coding RNAs are long transcripts with little/no protein coding capacity

Discovered through genome-wide sequencing ad transcriptome studies

Which organelles in the cell have their own DNA?

Only MITOCHONDRIA AND CHLOROPLASTS have their own DNA

Is mitochondrial DNA like Eukaryotic DNA or Prokaryotic DNA? Explain

Mitochondrial DNA is like Prokaryotic DNA in that it is small, circular, and highly coiled

Has no histones

Does mtDNA evolve at a faster or slower rate when compared to nuclear DNA?

mtDNA in animals EVOLVES 5-10 times faster than nuclear DNA

mtDNA in plants evolves 1/10 slower than nuclear DNA

Why can we say that the mitochondrial genome is one big operon?

The mitochondrial genome can be described as one big operon since it only has A SINGLE PROMOTER