Chapter 5: Cell Division [COMPLETE] Flashcards
what does the cell theory say about cell division?
that all cells arise from pre-existing cells through cell division
genome
all the DNA in a cell
chromosomes
separate DNA molecules that
make up the entire genome
homologous chromosome pairs
two different versions of the same chromosome number; one is inherited from mother and one from father
sister chromatids
identical, attached copies of a single chromosome that form dyads
dyads
replicated chromosomes containing two sister chromatids that look like an “X”
centromeres
regions of DNA that connect sister chromatids in a dyad
kinetochores
proteins on the sides of
centromeres that help microtubules pull sister chromatids apart during cell division
karyokinesis
division of the nucleus
cytokinesis
physical division of the
cytoplasm and cell membrane
what does 1 parent cell produce after division?
2 daughter cells
ploidy
describes the number of chromosome sets found in the body
why are humans diploid?
because they contain two sets of chromosomes (46 chromosomes, 23 pairs), one from each parent
besides diploid, what other cells do humans have? what is their other name and how many chromosomes?
haploid cells (gametes) that only contain one chromosome set (23 chromosomes)
how many pairs of sex chromosomes are there in the body? what do they determine?
one pair in the human body; they determine sex
what are autosomes and how many pairs are in the body?
they are nonsex chromosomes; 22 pairs in the body
gametes
haploid cells (sperm and eggs)
germ cells
diploid cells that divide by meiosis to produce gametes
gametocyte
eukaryotic germ cells that can either divide to form more gametocytes or produce gametes
somatic cells
all body cells excluding the
gametes; diploid in humans
what are the two main phases of the cell cycle, and which phase includes G1, G0, S, and G2?
interphase and M phase; interphase
what percentage of the cell cycle takes place during interphase, and what follows interphase in the cell cycle?
90%; mitosis and meiosis
during which phase of the cell cycle does karyokinesis and cytokinesis occur?
M phase
what is the bootcamp mnemonic that helps remember the key phases of the cell cycle?
Go = Gap Phase 1 (G1) of interphase
Sam = Synthesis Phase (S) of interphase
Go = Gap Phase 2 (G2) of interphase
Make = Mitosis of the M phase
Cake = Cytokinesis of the M phase
what happens during Gap phase 1 (G1) of the cell cycle?
cell grows in preparation for cell division; also checks for favorable conditions
what happens to the cells in G1 if favorable?
the cell will enter the S phase
what happens to the cells in G1 if unfavorable?
the cell will enter G0 phase
what occurs in the G0 phase of the cell cycle?
cells still carry out their functions but cells that do not divide are stuck here
what occurs during the Synthesis phase (S) of interphase, and what happens to centrosomes here?
cell replicates its genome here and moves to G2 phase when completed; centrosome duplicates
what occurs during the G2 phase of interphase? what is replicated here?
cell continues to grow and prepare for cell division by checking DNA for any errors after replication; organelles are replicated here
in addition to checking DNA for errors, what else do cells in G2 phase check for?
mitosis promoting factor (MPF) aka maturation PF, there must be an adequate amount for cell cycle to continue
where are Microtubule Organizing Centers (MTOCs) present in and what do they function in? what is it made of?
MTOCs are present in eukaryotic cells; they organize extension of microtubules, which are made of the protein tubulin
what are MTOCs responsible for forming?
the spindle apparatus
what does the spindle apparatus do?
guides chromosomes during karyokinesis
what are centrosomes and where are they found?
organelles that contain a pair of centrioles; found in animal cells
what do centrosomes act as?
MTOCs
what are the microtubules types in the spindle apparatus?
kinetochore, astral, and polar
where do kinetochore microtubules extend from and attach to?
extend from centrosomes and attach to kinetochores on chromosomes
where do astral microtubules extend from and attach to? why?
extend from centrosomes to the cell membrane to orient the spindle apparatus
where do polar microtubules extend from and attach to? why?
extend from the two centrosomes and connect with each other; they push centrosomes to opposite ends of the cell
what is the structural composition of centrioles, and how is it arranged?
they are hollow cylinders made of nine triplets of microtubules; (9x3 array)
Where are centrosomes typically located within a cell, and what is the orientation of the pair of centrioles found within a centrosome? what are they attached by?
near the nucleus; 90 degree angles to one another (attached to each other by interconnecting fibers)
where do centrosomes replicate and why?
during the S phase of the cell cycle so that each daughter cell after cell division has one centrosome
what material surrounds the centrioles and what is it responsible for?
pericentriolar material; responsible for microtubule nucleation (initiates the tubulin to start microtubule extension/production)
what is the structure and array of cilia and flagella?
nine doublets of microtubules with two singles in the center (9+2 array)
what are cilia and flagella produced by?
a basal body, which is initially formed by the mother centriole attaching itself to the cell membrane
what is karyokinesis?
nuclear division
what is mitosis (type) and what does it involve?
a type of karyokinesis; involves a diploid parent cell dividing into two diploid daughter cells
what are the four phases of mitosis?
prophase, metaphase, anaphase, telophase
what occurs in prophase and what structural changes occur?
chromatin condenses into chromosomes (X-shaped dyads); the nucleolus and nuclear envelope disappear, spindle apparatus forms
what occurs in prometaphase?
the nuclear envelope fragments, and spindle apparatus microtubules attach to the kinetochores of chromosomes
what occurs in metaphase?
the spindle apparatus guides the chromosomes to the metaphase plate (midpoint of cell) in a single file
what occurs in anaphase? what happens to chromosome number?
kinetochore microtubules shorten to pull sister chromatids apart, then, sister chromatids are considered separate chromosomes; chromosome number doubles
what occurs in telophase and what structural changes occur?
chromosomes segregate and nuclear membranes reform; nucleoli reappear and chromosomes decondense into chromatin; only eukaryotic cell DNA is organized into chromatin
what is cytokinesis?
the physical separation of the cytoplasm and cell membrane into two daughter cells
when does cytokinesis begin in animal cells?
begins in late anaphase with the formation of a cleavage furrow
what is the cleavage furrow?
a contractile ring of actin microfilaments and myosin motors that pinches the cell into two
when does cytokinesis begin in plant cells?
in telophase with the formation of a cell plate
what is the cell plate created by and what does is produce?
vesicles from the Golgi apparatus; middle lamella (which cements plant cells together)
how does the cell cycle influence cell division?
by having limitations and regulations to its growth to prevent cancerous growth
what are the two functional limitations of cell division?
surface to volume ratio (S/V), and genome to volume ratio (G/V)
surface to volume ratio (S/V)
cell division occurs when volume is too large because cells rely on the surface area of their cell membrane transport material; decrease in S/V ratio leads to cell division
genome to volume ratio (G/V)
cell division occurs when the volume of the cell is too large to be supported by the limited size of the genome; decrease in G/V ratio leads to cell division
what are the cell specific regulations of cell division?
cell specific checkpoints, cyclin-dependent kinases (CDKs), growth factors, density dependent inhibition, and anchorage dependence
[cell specific regulations] Cell specific checkpoints (G1 restriction point)
checks for favorable conditions to grow, enters G0 phase if unfavorable
Cell specific checkpoints (end of G2)
checks accuracy of DNA replication and MPF levels
Cell specific checkpoints (M checkpoint)
during metaphase, checks for chromosomal attachment to spindle fibers
[cell specific regulations]
cyclin-dependent kinases (CDKs)
CDKs phosphorylate certain substrates to signal cell cycle progression; activated by cyclin
what is cyclin?
a protein that cycles through stages of synthesis and degradation
[cell specific regulations]
growth factors
bind to receptors in the plasma membrane to signal for cell division
[cell specific regulations]
density dependent inhibition
halting of cell division when density of cells is high
[cell specific regulations]
anchorage dependence
cells divide only when attached to an external surface
why do organisms use mitosis?
to increase the number of cells in an organism
what is binary fission used by and for what?
by archaea, bacteria, and certain organelles (mitochondria, chloroplasts) to reproduce
what does binary fission lack?
spindle apparatus
what do organisms do in binary fission?
replicate their genome while cell division is happening (no S phase for DNA replication)
what does meiosis produce and from what?
produces four haploid daughter cells from one diploid parent cell
how does meiosis produce four haploid daughter cells from one diploid parent cell?
by repeating the steps of karyokinesis twice
what two phases can meiosis be divided into?
meiosis I (homologous chromosomes separate) and meiosis II (sister chromatids separate)
what does meiosis I (reductional division) produce and through what?
produces two haploid daughter cells through separation of homologous chromosomes
what occurs in prophase I and what structural changes occur?
chromatin condenses into chromosomes (X-shaped dyads); nucleolus and nuclear envelope disappear; homologous chromosomes pair up and crossing over occurs
[PROPHASE I] synapsis
the pairing up of homologous chromosomes to form tetrads (aka bivalents)
[PROPHASE I] synaptonemal complex
protein structure that forms between homologous chromosomes during synapsis
[PROPHASE I] tetrads (bivalents)
pair of two homologous chromosomes each with two sister chromatids
[PROPHASE I] chiasmata
where two chromosomes of a homologous pair cross over during synapsis, causing genetic recombination
[PROPHASE I] genetic recombination
exchange of DNA between chromosomes to produce genetically diverse offspring
what occurs in metaphase I? what does this contribute to?
tetrads randomly line up double-file on the metaphase plate; this contributes to genetic diversity
what occurs in anaphase I?
kinetochore microtubules shorten to separate homologous chromosomes from each other; will not begin unless at least one chiasmata has formed within each tetrad
what occurs in telophase I and what structural changes occur?
after tetrads have been pulled to opposite poles, nuclear membranes reform; in addition, nucleoli reappear and chromosomes decondense into chromatin
what occurs in cytokinesis I?
cleavage furrow forms in animal cells and a cell plate forms in plant cells
what occurs in meiosis II and why is it similar to mitosis?
two haploid cells divide into four haploid daughter cells; similar to mitosis because sister chromatids are separated
what occurs in prophase II and what structural changes occur?
chromatin condenses into chromosomes (X-shaped dyads), nucleolus and nuclear envelope disappear, spindle apparatus forms, no crossing over occurs
what occurs in metaphase II?
chromosomes line up single-file at the metaphase plate just like in mitosis
what occurs in anaphase II?
kinetochore microtubules shorten to pull sister chromatids apart; sister chromatids become separate chromosomes and chromosome number doubles
what occurs in telophase II and cytokinesis II and what structural changes occur?
nuclear membranes reform, nucleoli reappear, and chromosomes decondense into chromatin (only in eukaryotic cells); 4 haploid daughter cells are produced in total
Chromosome and Chromatid Numbers: Mitosis
s phase: 46 chromosomes duplicate
afterward: 46 chromosomes, 92 chromatids
metaphase: line up individually
anaphase: sister split; 92 separate chromosomes, 92 chromatids
end (per cell): 46 chromosomes, 46 chromatids
DIPLOID!!
Chromosome and Chromatid Numbers: Meiosis I
s phase: 46 chromosomes duplicate
afterward: 46 chromosomes, 92 chromatids
metaphase: line up doubled up (tetrad)
anaphase: homologous chromosomes split; 46 chromosomes, 92 chromatids
end (per cell): 23 chromosomes, 46 chromatids
Chromosome and Chromatid Numbers: Meiosis II
metaphase: line up individually
anaphase: sister separate; 46 chromosomes, 46 chromatids
end (per cell): 23 chromosomes, 23 chromatids
HAPLOID!!
if a question is giving me an n (4n=8) type equation and its asking what it appears as in anything that is meiosis II, then
the 4n=8 is applicable to meiosis I ONLY!!! so you would divide in half and that’s how it starts in meiosis II, then apply the question
