BIOL 189: Chapter 8 - DNA Replication Binary Fission and Mitosis

What does a gene contain?

Instructions for building RNAs & proteins

What is a genome?

The complete DNA sequence for a particular organism or individual

What is gene expression?

The information encoded in a gene is transcribed and then translated into a protein

What is cell theory?

All cells come from other cells

How do cells reproduce?

By division, one cell divides into two cells

What is apoptosis?

programmed cell death

What precedes cell division?

DNA replication

Where does DNA replication begin in the DNA?

origins of replication

What structural feature forms when DNA opens up at the origin?

A replication fork

What proteins are involved in DNA replication?

Helicase and DNA polymerase

What is the function of DNA polymerase in DNA replication?

It replicates and copies the DNA template strand to build the new strand

What is the function of Helicase in DNA replication?

It unwinds and opens the double-stranded DNA helix

What is cell division in prokaryotes?

Binary fission

What are the steps of binary fission?

1. DNA replication

2. Cell elongation

3. Septation

4. Cell pinches off

What is horizontal gene transfer?

When bacteria acquire new genes from source organisms other than their parent cell

What occurs during bacterial transformation?

A bacterium picks up exogenous (outside), naked DNA from its surrounding environment

What occurs during bacterial conjugation?

One bacterium directly transfers a copy of plasmid DNA to another bacterium through a physical connection

What occurs during bacterial transduction?

A virus (bacteriophage) delivers new DNA into a recipient bacterium

What are the three primary mechanisms of horizontal gene transfer?

Transformation

Transduction

Conjugation

What must a eukaryotic cell do before it divides?

It must replicate its entire genome so each new cell receives an identical copy of DNA

What is the general mechanism used to replicate DNA?

Unzipping the double helix and using each original strand as a template to synthesize a new complementary strand

What molecules mediate the unwinding and synthesis of DNA?

Enzymes

What is chromatin, and what proteins are involved in its formation?

Chromatin is a structure where DNA is wrapped around histone proteins

What are chromosomes?

Highly condensed (compacted) chromatin structures that carry genetic material

How many genes are arranged within the human chromosomes?

20,000

Why do human chromosomes exist in pairs?

Because you inherit one set from your maternal side, and one set from your paternal side

Which human chromosome carries the ABO gene that determines blood type?

Chromosome 9

What is the structural state of DNA in an undividing cell before mitosis begins?

Not condensed

What is considered the first step when a cell commits to cell division?

DNA replication

What specific structural effect does DNA replication have on chromatin before it condenses?

It duplicates the genetic material, leading to the formation of sister chromatids

At what specific phase of mitosis do the duplicated sister chromatids fully condense into distinct chromosomes?

During Prophase

In which specific part of the cell cycle does chromosome replication/duplication occur?

S-phase of interphase

What are the two strands of a replicated chromosome called before they separate?

Identical sister chromatids

What is the structural region that holds identical sister chromatids together?

Centromere

When does the duplicated DNA finally condense into visible two-sister chromatid structures?

After duplication, during the prophase of mitosis

How do chromosomes visually differ between duplicated and unduplicated karyotypes on a slide?

Duplicated appear as X shapes, unduplicated appear as single vertical lines

What is the overarching sequence of cellular growth and division known as?

The cell cycle

What are the two primary divisions of the cell cycle

Interphase and cell division

During which specific phase of interphase does DNA duplication take place?

S-phase

In which phase of mitosis does DNA condensation into visible sister chromatids occur?

Prophase

What are the four main sequential stages of mitosis?

Prophase

Metaphase

Anaphase

Telophase

What final process follows mitosis to complete cell division?

Cytokinesis

What is the primary function of the cell during the G1 phase?

Normal cell functions and cell growth

What is the main purpose of the G2 phase?

Additional growth and preparation for mitosis

What is the definition of mitosis?

The splitting of sister chromatids of a duplicated chromosome and the relocation of daughter chromosomes to opposite locations in the cell

What are the transport "rails" of the cell?

Microtubules

What are the three cellular structures involved in moving cargo across the microtubule monorail?

Transport vesicle

Motor proteins

Microtubule

What are centrosomes defined as?

Organelles where microtubules are synthesized and organized

During which specific phase of interphase do centrosomes duplicate?

G2 phase

What critical quality control check does the cell perform during G2?

The cell checks for complete DNA replication

What are the 4 end results of prophase

1. DNA condenses into chromosomes

2. Nuclear membrane disintegrates

3. Centrosomes move to opposite poles/sides of the cell, synthesizing microtubules

4. Chromosomes begin to move toward equatorial plane of cell

What structural events define early prophase

Chromosomes condense and becomes visable, spindle forms as centrosomes move to opposite poles.

What structural events define late prophase

The nuclear envelope breaks up, and spindle fibers attach to the chromosomes

What major structure forms during the transition to metaphase

The spindle apparatus

Where do spindle microtubules attach on a duplicated chromosome?

To the sister chromatids of each chromosome

What are the specific microtubules called that attach directly to the chromosome?

Kinetochore microtubules

What cage-like structure is fully formed by microtubules during metaphase?

The mitotic spindle

What is the signature visual feature of chromosomes during metaphase?

They line up in a single file line at the spindle midline

What are the two names given to the cell equator where chromosomes align?

The spindle midline or the metaphase plate

What happens to sister chromatids during anaphase?

They are pulled apart by the mitotic spindle, turning into individual daughter chromosomes

Where are the separated daughter chromosomes pulled toward?

To opposite poles of the cell

What physical change happens to the shape of the cell as a whole during anaphase?

The cell continues to elongate

What structural change occurs to the centromere at the start of anaphase?

The centromere splits, separating the two identical daughter chromosomes.

What structural change happens to chromosomes during telophase?

They de-condense

What happens to the nuclear membrane and nucleolus during telophase?

The nuclear envelope and nucleolus reform at each pole around the chromosomes.

What happens to the mitotic spindle microtubules during telophase?

They begin to disintegrate / disappear.

What forms at the equatorial plane during telophase to prepare for cytokinesis?

Two sets of protein filaments.

What is the fundamental definition of cytokinesis?

The division of the cytoplasm into two distinct cells.

What physical structure forms to pinch the animal cell apart during cytokinesis?

A contractive ring composed of protein filaments.

What stage follows cytokinesis, and what do the newly formed cells do?

G1 of early interphase, where cells resume normal functions or prepare to enter another division cycle.

What are the three types of cytoskeletal filaments

microfilaments, intermediate filaments, microtubules

What is the primary function of microfilaments

changes in cell shape.

What are the three main functions of microtubules

Maintenance of cell shape, movement of organelles, and cell mobility

Which cytoskeletal component specifically mediates cytokinesis

Microfilaments

Which cytoskeletal component specifically mediates mitosis

Microtubules

How does the mechanism of cytokinesis differ between plant cells and animal cells?

Animal cells divide using a cleavage furrow, while plant cells divide by cell plate formation.

What cellular structures compose the forming cell plate in plant cells during cytokinesis?

A compound of vesicles

What rigid structural feature prevents plant cells from pinching inward with a cleavage furrow like animal cells?

The cell wall

What is eventually formed at the midline once plant cell cytokinesis is complete?

Two cell walls separating the individual daughter cells.

What structural cytoskeletal components help to organize the cell plate assembly area?

Microtubules

What is the primary question asked at the G1 phase checkpoint?

Is there a signal to divide?

What three crucial questions are evaluated at the G2 phase checkpoint?

Is the genome properly replicated?

Is the genome damaged? Does the cell have the resources to continue into mitosis?

What is the vital quality control check during Mitosis before chromosomes separate?

Did the mitotic spindle attach correctly to the chromosomes for correct separation?

When does a cell undergo apoptosis?

When it sustains irreparable damage

What is a tumor defined as?

A mass of cells undergoing uncontrolled cell division.

What is metastasis?

The spread of cancer from one location to another within the body.

What is the underlying genetic reason given for why the cell cycle goes wrong?

Mutations in checkpoint genes.

What specific molecular consequences do checkpoint gene mutations have on the cell cycle?

They cause mutations in proteins that are directly involved in executing cell cycle checkpoints, leading to unregulated cell division.

If a protein involved in a cell cycle checkpoint is mutated, what normally protective process from the previous slides fails to happen when DNA is damaged?

Apoptosis is not triggered, allowing damaged cells to survive and divide.

What structural feature keeps a benign tumor from spreading to other parts of the body?

A capsule of connective tissue

What are malignant tumor cells capable of doing throughout the body?

They can "seed" new tumors in distant locations.

What two major internal transport systems do malignant cancer cells use to travel and spread?

Lymph vessels and blood vessels

What happens during the actual process of metastasis?

Malignant cells break away from the primary tumor, enter blood or lymph vessels, and travel to form a new tumor in another part of the body.