BSC 2010 Chapters 12 and 13 Review Flashcards

150 vocabulary flashcards covering the concepts, phases, and mechanisms of cell division (mitosis and meiosis) as described in chapters 12 and 13.

Single-celled organism division reason

Reproduction is the only reason for cells to divide in these organisms.

Single-celled organism division types

Binary fission and mitosis.

Multicellular organism division reasons

Growth and development, and repair/regeneration.

Multicellular organism division types

Mitosis and meiosis.

Interphase

A main part of the cell cycle consisting of the $G1$, $S$, and $G2$ phases.

M Phase

The part of the cell cycle consisting of mitosis and cytokinesis.

$G1$ Phase

A phase that separates $M$ and $S$ phases where the cell grows physically larger and prepares for the next phase.

$G2$ Phase

A phase that separates $S$ and $M$ phases where the cell grows physically larger and prepares for mitosis.

$S$ Phase

The phase where DNA synthesis occurs and the cell replicates its genetic material.

Chromosome duplication purpose

To create a complete identical copy of DNA in the nucleus so both future daughter cells have an entire set of chromosomes.

Mitosis

The process of the division of the nucleus.

Cytokinesis

The process of the division of the cytoplasm.

$G0$ Phase

A resting or nondividing phase outside of the active cell cycle.

$G0$ Phase entry point

A cell decides to enter this phase during the $G1$ phase.

Tissue-specific cell division frequency

Variation in division rates in adult multicellular organisms directly tied to the specific function of the tissue.

DNA

The fundamental double stranded molecule that encodes genetic instruction for development, functioning, growth, and reproduction.

Gene

A specific segment or sequence of DNA along a chromosome that contains instructions to make a functional product.

Chromatin

The loose, uncoiled, and relaxed form of genetic material consisting of DNA wrapped around histones.

Histones

Structural proteins around which DNA is wrapped to form chromatin.

Chromosome

A single continuous structural unit of genetic material formed when chromatin condenses.

Replicated chromosome

A structure consisting of two DNAs and a chromatid, comprised of two identical sister chromatids.

Sister chromatids

Two identical halves of a single replicated chromosome that are exact duplicates of each other.

Genome

The complete entire set of genetic material or DNA contained within an organism or cell.

Histones (Packing function)

Act as a spooling mechanism to physically pack massive amounts of DNA into the tiny nucleus.

Histones (Regulation function)

Act as gatekeepers that dictate whether a gene can be read by the cell to make proteins.

Interphase chromatin appearance

Loose form ideal for accessing, reading, and replicating genetic information.

M phase chromatin appearance

Chromatin packs so tightly that individual chromosomes become clearly visible.

Prophase chromosome appearance

Chromosomes begin to condense into distinct, visible threads as two identical sister chromatids.

Prophase nuclear envelope status

Remains intact but begins to prepare for breakdown; the nucleolus disappears.

Prophase mitotic spindle appearance

Begins to form out of tubulin proteins with centrosomes moving toward opposite poles.

Tubulin

The proteins that make up the mitotic spindle.

Centrosome

Organelle from which the mitotic spindle forms and moves toward opposite poles.

Prometaphase chromosome state

Chromosomes finish condensing and are highly compact with kinetochores developed on the centromere.

Kinetochore

Specialized protein complexes that develop on the centromere of each chromosome.

Prometaphase nuclear envelope status

Completely fragments and breaks apart, allowing spindle microtubules to invade the nuclear area.

Kinetochore microtubules

Spindle fibers that attach securely to the handles on chromosomes to jerk them back and forth.

Nonkinetochore microtubules

Microtubules that extend across the cell and overlap with those from the opposite pole.

Metaphase alignment

Chromosomes are pulled into a strict alignment right down the center of the cell.

Metaphase plate

The imaginary plane down the center of the cell where chromosomes align.

Metaphase nuclear envelope status

There is no nuclear envelope present during this stage.

Metaphase mitotic spindle status

Fully mature with centrosomes firmly anchored at exact opposite poles.

Anaphase chromosome action

Centromeres split and sister chromatids are abruptly pulled apart toward opposite poles.

Daughter chromosome

The status of an individual chromatid once it has been separated during anaphase.

Anaphase chromosome shape

A \"V\" or \"Y\" shape as they are dragged backward through the cytoplasm.

Anaphase microtubule action

Kinetochore microtubules rapidly shorten or depolymerize at their kinetochore ends.

Anaphase cell elongation

Caused by nonkinetochore microtubules pushing against one another.

Telophase chromosome state

Chromosomes reach opposite poles and begin to relax, uncoil, and decondense back into chromatin.

Telophase nuclear envelope status

A new nuclear envelope reforms around each set of chromosomes using fragments of the parent membrane.

Telophase mitotic spindle status

The spindle completely breaks down and subunits are depolymerized back into the cytoskeleton pool.

Cytoskeletal fibers in division

Microtubules made of tubulin and microfilaments made of actin.

Mitotic spindle reorganization

The interphase microtubule network dismantles and rebuilds into an apparatus to move chromosomes.

Actin (Cytokinesis function)

Microfilaments that step in to handle the mechanical work of pinching the cell into two.

Homologous chromosomes

Pairs in a diploid organism that are the same length, have the same centromere position, and carry the same genes.

Origin of homologous pairs

Result of sexual reproduction where one of each pair is inherited from each parent.

Autosomes

Chromosomes containing genes for general body characteristics unrelated to biological sex.

Human autosome count

$44$ chromosomes, arranged in $22$ pairs.

Autosome homology

Always homologous as maternal and paternal chromosomes match in size, shape, and gene composition.

Sex chromosomes

Chromosomes that primarily determine biological sex and secondary sexual characteristics.

Human sex chromosome count

$2$ chromosomes, forming $1$ pair.

Female sex chromosomes ($XX$)

Two chromosomes that are fully homologous sharing the same size, structure, and gene loci.

Male sex chromosomes ($XY$)

Chromosomes that are NOT truly homologous; the $X$ is much larger than the $Y$.

$X$ chromosome scale

Much larger chromosome carrying thousands of essential genes.

$Y$ chromosome scale

Much smaller chromosome carrying only a few dozen genes.

Somatic cells

General structural body cells that make up the vast majority of an organism's physical body.

Gametes

Specialized reproductive cells found exclusively within the reproductive system.

Somatic cell ploidy

These cells are diploid ($2n$).

Gamete ploidy

These cells are haploid ($n$).

Diploid ($2n$)

Containing two complete sets of chromosomes, one from each parent.

Haploid ($n$)

Containing only a single, unique set of chromosomes.

Human somatic chromosome number

Exactly $46$ chromosomes arranged into $23$ homologous pairs.

Human gamete chromosome number

Exactly $23$ chromosomes.

Somatic cell examples

Skin cells, liver cells, neurons, bone tissue, and muscle fibers.

Gonads

The specific locations where gametes are produced and located.

Testis

The male gonad where sperm is produced.

Ovaries

The female gonad where eggs or ova are produced.

Meiosis (General function)

Division that reduces the chromosome number by half, turning diploid cells into haploid gametes.

Fertilization

The process where a haploid sperm penetrates a haploid egg to merge genetic material.

Zygote

The single diploid ($2n$) cell resulting from fertilization.

Adult cell ploidy

Adult animals are made entirely of diploid cells ($2n$).

Multicellular growth mechanism

The zygote undergoes millions of rounds of mitosis to form a complex adult.

Prophase $I$ (Chromosomes)

Chromosomes condense and undergo synapsis to form tetrads where crossing over occurs.

Synapsis

The process where homologous chromosomes tightly pair up gene-for-gene.

Tetrad

A group of four chromatids formed by paired homologous chromosomes during synapsis.

Crossing over

The physical breaking and swapping of corresponding DNA segments between non-sister chromatids.

Chiasmata

X-shaped crossover points where chromosomes remain anchored together.

Prophase $I$ nuclear envelope status

The nuclear envelope completely breaks down and fragments.

Prophase $I$ spindle status

Centrosomes move to opposite poles and microtubules attach to kinetochores of homologous pairs.

Metaphase $I$ alignment

Homologous pairs align as double files along the metaphase plate.

Independent assortment

Random orientation of maternal and paternal chromosomes toward either pole during alignment.

Metaphase $I$ nuclear envelope status

Entirely absent.

Metaphase $I$ spindle attachment

Microtubules from opposite poles attach to the kinetochore of each homologue in a pair.

Anaphase $I$ chromosome action

Chiasmata break and homologous chromosomes separate toward opposite poles while sister chromatids remain attached.

Anaphase $I$ spindle function

Kinetochore microtubules shorten to pull homologues apart while nonkinetochore microtubules elongate the cell.

Telophase $I$ chromosome set

Each half of the cell has a complete haploid set of duplicated chromosomes.

Cytokinesis $I$

Splitting of the cytoplasm to form two distinct haploid daughter cells.

Meiosis $II$ Goal

The separation of sister chromatids.

Meiosis $I$ and $II$ pause

A brief pause between divisions without any DNA replication.

Prophase $II$ chromosome state

Chromosomes condense again as two sister chromatids that are no longer genetically identical.

Prophase $II$ nuclear envelope status

If reformed, nuclear envelopes fragment and disappear completely.

Metaphase $II$ alignment

Chromosomes align in a single, straight file along the metaphase plate.