Ch. 4: Genes and Cellular Function - Part 2 Flashcards

These flashcards cover various topics from Chapter 4, including protein secretion, gene regulation (specifically casein), the cell cycle, DNA replication, stages of mitosis, and cancer cell characteristics.

What are the two primary functions of the protein clathrin during the formation of transport vesicles in the rough ER?

It helps select proteins to be transported in vesicles and helps mold the forming vesicle.

Where do transport vesicles carry proteins after they detach from the rough endoplasmic reticulum?

To the nearest cisterna of the Golgi.

What specific type of modification does the Golgi complex add to proteins?

Carbohydrates.

Which part of the Golgi complex buds off new coated vesicles containing finished proteins?

The cisterna farthest from the ER (trans).

What are two possible fates for vesicles that bud off from the Golgi complex?

Some become lysosomes, while others become secretory vesicles.

By what process do secretory vesicles release their cell products?

Exocytosis.

What is an example of a cell type that permanently turns off a specific gene?

Liver cells turn off hemoglobin genes.

What can control variations in gene expression level from day to day or hour to hour?

Chemical messengers such as hormones.

What is the first step in the mechanism of gene activation for casein?

The hormone prolactin binds to receptors on the membrane of a mammary cell.

What protein is triggered by the binding of prolactin to mammary cell receptors?

A transcription activator protein.

Where does the transcription activator move to bind DNA near the casein gene?

The nucleus.

What enzyme is enabled to bind to the gene and transcribe it once the transcription activator binds to DNA?

RNA polymerase.

Where is the mRNA for casein translated in the mammary cell?

By ribosomes on the rough ER in the cytoplasm.

Which organelle packages casein into secretory vesicles for release?

The Golgi.

Into what substance does casein become part after being released from the cell?

Milk.

What are the two main phases included in the cell cycle?

Interphase and the mitotic phase.

What are the three sub-phases of interphase?

First gap phase ($G1$), Synthesis phase ($S$), and Second gap phase ($G2$).

What interval occurs during the $G1$ phase of the cell cycle?

The interval between cell division and DNA replication.

What is the primary activity that occurs during the $S$ phase?

DNA replication.

What tasks are performed by the cell during the $G2$ phase?

Repairs of DNA errors, growth, and protein synthesis that controls cell division.

Why must a cell duplicate its DNA before dividing?

To give a complete copy of all its genes to each daughter cell.

What principle allows for the prediction of the sequence of a new DNA strand during replication?

The Law of complementary base pairing.

What is the first step in the process of DNA replication?

Unwinding the helix from the histones.

Which enzyme is responsible for unzipping a small portion of the DNA helix?

DNA helicase.

What structure is formed when DNA strands are separated by helicase?

A replication fork.

What function does DNA polymerase serve during replication?

It synthesizes complementary strands.

What is the function of DNA ligase in DNA replication?

It connects the discontinuous strand.

Why is DNA replication described as semiconservative?

Because each daughter DNA molecule consists of one old strand and one new strand.

What is synthesized in step $4$ of DNA replication to organize new DNA strands into nucleosomes?

New histones.

What mechanism is responsible for correcting replication errors?

DNA Damage Response (DDR).

How frequently do errors occur in DNA replication after DNA polymerase double-checks the base pairs?

One error per $1 \text{ billion}$ bases replicated.

What are three environmental factors that can cause mutations in DNA structure?

Radiation, viruses, and chemicals.

What term describes the genetic variation within one's body due to mutations and replication errors?

Genetic mosaicism.

What is the outcome of mitosis?

Two genetically identical daughter cells.

What is the approximate number of cells an individual develops into from a fertilized egg?

About $50 \text{ trillion}$ cells.

What are the four phases of mitosis?

Prophase, Metaphase, Anaphase, and Telophase.

During which phase of mitosis does the genetic material condense into compact chromosomes?

Prophase.

How many chromosomes and sister chromatids per chromosome are present during prophase?

$46$ chromosomes, with two sister chromatids per chromosome.

What happens to the nuclear envelope during prophase?

It disintegrates.

At what location in the cell do chromosomes align during metaphase?

The cell equator (equatorial plate).

What is the lemon-shaped array of spindle fibers formed during metaphase called?

The mitotic spindle.

How do chromosomes migrate to each pole during anaphase?

Motor proteins in kinetochores crawl along spindle fibers.

What happens to the two sister chromatids during anaphase?

An enzyme cleaves them apart at the centromere.

Which organelle is responsible for making the new nuclear envelope during telophase?

Rough ER.

What state do chromosomes return to during telophase?

Chromatin (they uncoil).

What structures appear within each new nucleus formed during telophase?

Nucleoli.

What is the definition of cytokinesis?

The division of the cytoplasm.

Which two proteins are involved in pulling on the terminal web to achieve cytokinesis?

Myosin and actin.

What is the name of the crease created around the equator of the cell during cytokinesis?

The cleavage furrow.

List two conditions required for cells to divide.

They must have enough cytoplasm for two daughter cells and an adequate supply of nutrients.

What is contact inhibition?

The cessation of cell division in response to contact with other cells.

What are the two types of regulatory proteins involved in the cell cycle control system?

Cyclins and cyclin-dependent kinases (Cdks).

Why are cyclins named as such?

For their cyclically fluctuating concentrations in the cell.

What must occur for a cyclin-dependent kinase (Cdk) to be active?

It must be attached to a cyclin.

What specific cyclin-Cdk complex triggers the cell's passage past the $G2$ checkpoint into the M phase?

MPF (maturation-promoting factor).

What is an example of an external chemical growth factor?

Platelet-derived growth factor (PDGF).

What type of cell fragments produce PDGF?

Platelets.

In physical signaling, what happens during density-dependent inhibition?

Crowded cells stop dividing.

What is anchorage dependence?

The requirement that cells must be attached to a substrate to divide.

How do cancer cells differ from normal cells regarding growth factors?

They may make their own growth factor or convey signals without the growth factor's presence.

What term describes cancer cells that have acquired the ability to divide indefinitely?

Transformation.

What is a mass of abnormal cells that remains at the original site?

A benign tumor.

What type of tumor invades surrounding tissues?

A malignant tumor.

What is metastasis?

The spread of cancer cells to other parts of the body.

What phase defines the start of the mitotic phase in terms of structural cell activity?

Prophase.