Bio 112 Chapter 10 Flashcards

A comprehensive set of flashcards covering prokaryotic and eukaryotic cell reproduction, the cell cycle, mitosis, regulation mechanisms, and the basics of cancer.

What is a cell's DNA packaged as a double stranded molecule called?

Its genome

How is the prokaryotic genome typically shaped?

One double stranded DNA molecule shaped like a loop or circle

What is the region holding genetic material in a prokaryotic cell?

The nucleoid

What are plasmids?

Smaller loops of DNA carried by some prokaryotes that are not essential for normal growth

How do bacteria often trade helpful new genes such as antibiotic resistance?

Through plasmid exchange

Describe the eukaryotic genome structure.

A genome made up of several double stranded linear DNA molecules

How many chromosomes are in human body (somatic) cells?

$46$ chromosomes

How many chromosomes do human gametes carry?

$23$ chromosomes each

What is a diploid cell?

A cell holding two matched sets of chromosomes, one from each parent

What letter is used to stand for one chromosome set?

$$n$$

How is the chromosomal setup of a diploid cell written?

$$2n$$

What are cells carrying just one chromosome set called?

Haploid

How is a haploid cell configuration written?

$$1n$$

Which human cells are haploid?

Gametes, specifically eggs and sperm

What are homologous chromosomes?

Matched chromosome pairs formed when fertilization brings gametes together

What is a locus?

The same spot on homologous chromosomes where the same genes are carried

What are genes?

Functional pieces of chromosome that code for specific proteins that determine specific characteristics

How does the transcript distinguish between a characteristic and a trait?

A characteristic is a category like hair color, while traits are specific versions like blonde or brown

What are alleles?

Slightly altered nucleotide sequences within a gene that can produce alternative traits

Give an example of characteristics determined by three possible alleles.

Blood types $A$, $B$, and $O$

What is the percentage of DNA sequence difference between any two people?

Far less than $1$ percent

Which chromosomes are the single exception to the rule of homologous chromosome uniformity?

The sex chromosomes $X$ and $Y$

What is the relationship between chromosomes and genes?

A chromosome is a packaged DNA molecule that carries many genes along its length

Where is a gene located on a chromosome?

At a segment called a locus

How long would the DNA from all $46$ chromosomes in a human cell stretch if laid end to end?

About $2$ meters

What is the diameter of a DNA strand?

$$2,nm$$

What is the approximate width of a typical human cell?

$$10,μ m$$

Why must long DNA strands condense into compact chromosomes?

To fit inside the nucleus while remaining accessible for gene expression

What is chromatin?

A DNA-histone complex formed when DNA wraps around histone proteins

How many histone proteins make up the core of a nucleosome?

$8$ histone proteins

What is a nucleosome?

A beadlike histone-DNA complex

What connects nucleosomes in a chromatin structure?

Linker DNA

How much shorter is the DNA molecule in the nucleosome bead form compared to the plain double helix?

About $7$ times shorter

What is the width of a nucleosome bead?

$$10,nm$$

What is the second level of DNA compaction?

Nucleosomes and linker DNA coiling into a $30,nm$ chromatin fiber

By how much does the second level of compaction shorten the chromosome?

About $50$ times shorter than the extended form

What is the third level of DNA compaction?

Variety of fibrous proteins packing chromatin down and confining each chromosome to its own area of the nucleus

When does DNA replicate during the cell cycle?

During the $S$ phase of interphase

What is formed after DNA replication has occurred in the $S$ phase?

Chromosomes made up of two linked sister chromatids

What proteins bind identically packed sister chromatid pairs together?

Cohesin proteins

What is the centromere?

The tightest connection point and most condensed region between sister chromatids

What is the approximate width of joined sister chromatids under a light microscope?

$$1,μ m$$

Define the cell cycle.

An ordered sequence of events involving cell growth and division that produces two new daughter cells

What are the two major phases of the cell cycle?

Interphase and the Mitotic phase

What primarily happens during interphase?

The cell grows and DNA gets replicated

What happens during the mitotic phase?

Replicated DNA and cytoplasmic contents get separated

What is karyokinesis?

Nuclear division (mitosis)

What is cytokinesis?

Physical separation of cytoplasmic components into two daughter cells

What are multinucleate cells?

Cells with multiple nuclei produced when interphase and mitosis occur without cytokinesis

List the three stages of interphase.

$G_1$, $S$, and $G_2$

What occurs during the $G_1$ phase (first gap)?

Building raw materials for DNA and proteins and storing energy reserves for replication

What is produced during the $S$ phase (synthesis of DNA)?

Identical pairs of DNA molecules called sister chromatids attached at the centromeric region

What organelles, responsible for managing chromosome movement, duplicate during the $S$ phase?

The centrosomes

What is the mitotic spindle?

An apparatus that manages chromosome movement during mitosis

Describe centrioles.

A pair of rodlike structures positioned at right angles that help organize cell division in most animal cells

Which eukaryotes generally lack centrioles?

Plants and most fungi

What are the primary activities of the $G_2$ phase?

Replenishing energy stores, synthesizing proteins to move chromosomes, and duplicating some organelles

What happens to the cytoskeleton during the $G_2$ phase?

It dismantles to free up resources for the mitotic phase

What are the two main parts of the mitotic phase?

Karyokinesis (mitosis) and cytokinesis

List the five phases of karyokinesis.

Prophase, prometaphase, metaphase, anaphase, and telophase

What happens to the nuclear envelope and organelles in prophase?

The nuclear envelope dissociates into vesicles, and the Golgi complex and endoplasmic reticulum fragment

What happens to the nucleolus during prophase?

It disappears

What proteins assist in the tight coiling of sister chromatids during prophase?

Condensin proteins

What is the defining characteristic of prometaphase?

The advancement of prophase processes and the binding of kinetochores to spindle microtubules

What is a kinetochore?

A protein structure at the centromeric region of each sister chromatid that attracts and binds spindle microtubules

What are polar microtubules?

Spindle microtubules not attached to chromosomes that help elongate the cell

What is the role of astral microtubules?

Helping to orient the mitotic spindle near the poles

What is the metaphase plate?

A plane midway between the two poles where all chromosomes line up during metaphase

At what phase do chromosomes reach their most condensed state?

Metaphase

What happens to cohesin proteins during anaphase?

They degrade

What is the movement of chromatids during anaphase?

Each chromatid, now a chromosome, is pulled rapidly toward the centrosome by its microtubule

How does the cell shape change during anaphase?

It visibly elongates into an oval shape as polar microtubules slide against each other

What occurs during telophase?

Chromosomes reach poles, decondense back into chromatin, spindles depolymerize, and nuclear envelopes form

According to the transcript, what reappears within the nuclear area during telophase?

Nucleosomes

How is cytokinesis defined?

"Cell motion," completing division by physically separating cytoplasmic components into two daughter cells

Describe cytokinesis in animal cells.

A contractile ring of actin filaments pulls the cell's equator inward, forming a cleavage furrow

How does cytokinesis differ in plant cells?

A new cell wall must form between daughter cells using Golgi vesicles and a phragmoplast

What is the phragmoplast?

A vesicular structure formed at the metaphase plate by Golgi vesicles traveling on microtubules in plant cells

What is the cell plate?

A structure formed by fusing Golgi vesicles that enlarges to merge with cell walls, creating a new wall

Where does the glucose come from for building a new plant cell wall during cytokinesis?

From the Golgi apparatus, which stored it up during interphase

What happens to the Golgi membranes after the plant cell plate is formed?

They become part of the plasma membrane on either side of the new cell wall

What is the $G_0$ phase?

A quiescent (inactive) stage where cells exit the cell cycle and are not actively preparing to divide

Why might a cell enter $G_0$ temporarily?

Due to environmental conditions like nutrient availability or stimulation by growth factors

Identify cell types that stay in $G_0$ permanently.

Mature cardiac muscle cells and nerve cells

What is the average duration of the cell cycle for epithelial cells?

$2$ to $5$ days

What is the length of a standard lab-grown cell cycle and its phases?

$24$ hours total; $G_1$ is $9$, $S$ is $10$, $G_2$ is $4.5$, and $M$ is $0.5$ hours

How fast do fertilized fruit fly eggs complete a cycle, and what is the outcome?

$8$ minutes, resulting in a multinucleate zygote due to lack of cytokinesis

What are examples of external events that regulate the cell cycle?

Nearby cells dying, release of growth promoting hormones, cell crowding, or cell size

How does HGH affect cell division?

Too little $HGH$ can lead to dwarfism, while too much can result in gigantism

Why does cell size initiate division?

As a cell grows, its surface-to-volume ratio drops, making it physiologically less efficient

What are cell cycle checkpoints?

Points where a cell's progress can be halted until conditions are favorable

Where do the three main cell cycle checkpoints occur?

Near the end of $G_1$, at the $G_2/M$ transition, and during metaphase

What is the G1 checkpoint often called in yeast?

The restriction point

What does the $G_1$ checkpoint check for?

Adequate reserves, cell size, and genomic DNA damage

What is the secondary outcome for a cell that fails the $G_1$ checkpoint besides halting?

It can advance into $G_0$ to await better conditions

What are the two most important things confirmed at the $G_2$ checkpoint?

Every chromosome has replicated and the replicated DNA is not damaged

What is the alternative name for the $M$ checkpoint?

The spindle checkpoint

What is the primary determination of the $M$ checkpoint?

Whether all sister chromatids are correctly attached to spindle microtubules

Why will the cell cycle not proceed past the $M$ checkpoint if kinetochores are not anchored?

Separating sister chromatids during anaphase is an irreversible step

What are the two groups of intracellular regulatory molecules?

Positive regulators and negative regulators