BISC 101-Cell Biology

The Cell Cycle

100

What are the functions of cell division in multicellular organisms such as humans?

For growth & development

Repair of damage to tissues

For reproduction of identical cells (mitosis)

200

Describe what is meant by "Interphase" in the cell cycle. Describe what is taking place in each phase.

Interphase is a combination of 3 phases: G1, S, and G2.

G1= the first gap phase; cell growth occurs

S= synthesis of DNA

G2= the second gap phase; cells prepare for cell division

300

Describe the changes that take place in the cell during telophase.

The spindle apparatus breaks down, the nuclear envelope forms around chromosomes, and the chromosomes de-condense.

400

What is a "checkpoint" in the cell cycle? What is their purpose?

A checkpoint is a location in the cell cycle that can stop/start the cell cycle.

The purpose of checkpoints is to regulate cell division. They determine when, and how much cell division is required. Without checkpoints, unregulated cell division would occur, potentially resulting in cancer.

500

What is MPF? Describe how it works in the cell.

MPF= mitosis promoting factor

MPF is a protein kinase, which combines with cyclin to allow mitosis to occur.

Cyclin phosphorylates the kinase (CDK), which, when combined with cyclin, forms MPF, which signals for mitosis to begin. At the end of mitosis, the MPF (cyclin) is degraded, and mitosis stops.

Cancer & COVID

100

List 2 ways by which cancer cells differ from normal healthy cells

Cells continue to grow and divide

Variations in size and shape of cells

Nucleus of cells is larger and darker

Abnormal number of chromosomes in cells, which are arranged in a disorganized fashion

Clusters of cells without boundaries

200

What is the suspected origin of the COVID-19 virus?

The suspected origin of the COVID-19 virus are infected horseshoe bats or pangolins in the Wuhan region of China.

300

Describe how proto-oncogenes and tumour-suppressor genes can be involved in cancer development.

When mutations occur in DNA, proto-oncogenes can change into cancer causing oncogenes. Mutations can also result in the inactivation of tumour suppressor genes, which can lead to the proliferation of cells and result in cancer.

400

How does chemotherapy work in the human body to reduce cancer growth?

Chemotherapy is used to kill rapidly dividing cells. Destroys spindle tube formation. However, it is non-specific and will also kill non-cancerous cells.

500

How does COVID-19 infect human epithelial cells?

A spike protein on the viral surface binds to ACE-2 (angiotension-converting enzyme), which is an abundant enzyme in the cell membranes of epithelial cells of the trachea, alveoli, heart, liver, kidney, and intestine. After binding, the virus uses furin (a host cell protease) to cut into a second spike protein, which facilitates the fusing of viral and host cell membranes to allow the virus to enter and release its mRNA. Viral replication then uses host cell components aided by the viral replicase to produce virion proteins composed from the host cell. The viral outer membrane originates from the host endomembrane system.

Cellular Transport & the Membrane

100

What does the term "amphipathic" mean?

• Amphipathic = a structure which has a hydrophilic and hydrophobic region

200

Distinguish between the terms isotonic, hypertonic and hypotonic

• Isotonic- an environment where the solute concentration is at equilibrium.
• Hypertonic- an environment where the solute concentration outside the cell is higher than the solute concentration inside the cell.
• Hypotonic- an environment where the solute concentration outside the cell is lower than the solute concentration inside the cell.

300

Discuss how cystic fibrosis in humans is associated with membrane transport deficiency.

A non-functioning chloride transport protein in the cell membrane causes cystic fibrosis in humans, resulting in sticky mucus being built up in the extracellular matrix.

400

Describe 3 types of passive transport (no energy required) across the cell membrane.

• Diffusion- movement of molecules down a concentration gradient to occupy available space until equilibrium is reached.
• Osmosis- movement of water from a region of low solute to a region of high solute.
• Facilitated diffusion- transport proteins in the cell membrane provide channels through which molecules can move from a high to low concentration gradient.

500

What is the purpose of a sodium-potassium pump and how does it work?

• Sodium inside the cell can build up to toxic levels and must be taken out. To balance the ionic charge, potassium is taken in. This occurs against a gradient, where sodium may already be high outside the cell. To maintain the negative charge inside the cell, three sodium leaving the cell is balanced by two potassium entering the cell in an ATP driven process.

DNA Replication

100

What does Helicase do?

Unwinds the parental DNA strands

200

What is an Okazaki fragment? What is the role of this during DNA replication?

• An Okazaki fragment is a stretch of DNA on the lagging strand that is added as a small unit to allow for replication in a 5’ to 3’ manner.

300

How does the cell repair any damage that may have occurred to its DNA?

• Mismatch repair- the damaged area is cut out by a nuclease, new nucleotides are added by DNA polymerase III, and the ends are joined by DNA ligase.

400

What are the functions of DNA polymerase III and DNA polymerase I in a cell?

• DNA polymerase III adds nucleotides to a new DNA strand at the position of the primer.
• DNA polymerase I replaces the RNA primers in the new DNA strands with DNA nucleotides.

500

What is meant by the “end-replication problem”? Describe the impact it could have on the cell.

• The very last primer on the lagging strand cannot be replaced by DNA polymerase I as there is no site for it to attach. As a result, the DNA molecule gets shorter with each cycle of replication, which can result in cell death.

DNA Technology

100

What is gene therapy?

Replacement of a nonfunctional allele of a gene with a functional allele. 

200

What is an RFLP? How is it created? 

RFLP= Restriction Fragment Length Polymorphism.

Created by restriction enzymes that cut DNA at specific sites to produce unique patterns. 

300

What is PCR? How does it work?

PCR=Polymerase Chain Reaction

Amplifies DNA- produces many copies using a denaturation, annealing, and elongation cycle

400

What is genetic testing? Give an example of what genetic testing can be used for.

Genetic testing allows a person's DNA to be tested for the presence of genes that could eventually cause problems in the future.

Tests for different circumstances:

To determine carrier status

To diagnose a specific disorder

To test prenatally for conditions

To screen newborns 

To determine future risks

To test fertilized eggs prior to implantation

For forensic investigations

500

Describe the basic process of how to recombine DNA in a bacterium

1. Gene of interest is inserted into a bacterial plasmid.

2. Plasmid is put into bacterial cell.

3. Host (bacterial) cell is grown in culture to form a clone of cells containing the "cloned" gene of interest.

4. This can be used for various applications and future research.