chapter 10 Flashcards
1
Q
bacteria
A
- genome made of a single, circular DNA molecule
- DNA found in nucleoid; distinct from cytoplasm
2
Q
binary fission
A
asexual reproduction by division of one cell into 2 equal parts (in bacteria); chromosome is replicated and 2 products are partitioned to each end of the cell prior to division
3
Q
steps of binary fission
A
- replication of bacterial DNA at a specific site
- proceeds both directions around circular DNA to site of termination
- grows by elongation and division occurs at midcell
4
Q
bidirectional DNA replication steps
A
- before division, the molecule replicates at origin of replication (specific site)
- replication enzymes move in both directions and make copies of each strand in DNA duplex (continue until they meet at terminus)
- as DNA replicates, cell elongates and DNA partitions so origins are at 1/4 and 3/4 positions and termini are in the middle of the cell
- septation - new membrane and cell wall material begin to grow and form a septum at midpoint (FtsZ facilitates this process)
5
Q
septum
A
a wall between 2 cavities
5
Q
septation
A
formation of septum where new cell membrane and cell wall are formed into separate daughter cells (prokaryotic)
1. formation of a ring composed of many copies of FtsZ
2. accumulation of other proteins
3. contracts inwards radially until cell pinches into two new cells
5
Q
FtsZ protein
A
found in most prokaryotes including archaea - can form filaments (rings, high degree of similarity to eukaryotic tubulin)
6
Q
haploid # of chromosomes
A
defines a species
7
Q
diploid
A
2n (total # of chromosomes)
8
Q
human (chromosomes)
A
haploid = 23, diploid = 46
9
Q
maternal + paternal chromosomes
A
homologous (individual = homologue)
10
Q
variations in a chromosome
A
- size
- staining properties
- location of centromere
- relative length of 2 arms around centromere
11
Q
karyotype
A
depicts morphology of chromosomes of an organism with a light microscope
12
Q
chromatime
A
what chromosomes are composed of
13
Q
chromosomes
A
- site of RNA synthesis
- has ~140 million nucleotides
14
Q
DNA compaction
A
DNA is compacted so that it can fit in a cell
15
Q
nucleosome
A
a complex consisting of a DNA double helix wound around a core of 8 histone proteins
16
Q
duplex
A
DNA double helix
17
Q
histone proteins
A
- 8 proteins with an overall positive charge
- have a positive charge because of an abundance of amino acids and lysine (causing it to be strongly attracted to negatively charged DNA)
18
Q
primary histones
A
H2A, H2B, H3, and H4 - associate together to form a complex with two of each histone to form an octamer
19
Q
octamer
A
acts as a spool that DNA is wound around
20
Q
linker DNA
A
a variable length of DNA (20-80 bp) that separates each histone octamer
21
Q
H1
A
histone that can interact with linker DNA
22
Q
solenoid
A
when isolated DNA wrapped in nucleosomes is incubated under low salt conditions with H2, it forms a compact structure which when coiled is a solenoid
23
organization
chromatin is organized into territories that have individual chromosomes which are further organized into compartments within each chromosome
24
topologically associated domains (TADs)
genomic regions interact to form these; involve loops of DNA in nucleosomes that are anchored at their base by two proteins
25
2 proteins at base that anchor DNA loops
- a DNA binding protein called CTCF and the cohesin complex or proteins
26
heterochromatin
inactive domains of chromatin
27
euchromatin
active domains of chromatin
28
state of chromatin
- between division = relatively diffuse
- during cell division = increasingly condensed to allow the separation of chromosomes
29
cell cycle patterns
- TADS in interphase disappear during prophase
- cohesin gets replaced with condensin (SMC proteins interact with DNA and induce loops in DNA)
30
condensin
protein complex involved in condensation of chromosomes during mitosis and meiosis
31
DNA replication
the molecule in each chromosome becomes 2 identical molecules held together at centromere by cohesins
- the greater the condensation, the greater the visibility of the X shape
- one chromosome but two sister chromatids
32
cohesin
a protein complex that holds sister chromatids together during cell division
- loss of cohesins at centromere allows anaphase movement of chromosomes
33
gap phase 1 (G1)
primary growth phase, fills gap between cytokinesis and DNA synthesis (longest phase)
34
synthesis (S) phase
cell synthesizes genome replica
- each chromosome replicates to produce two sister chromatids attached at the centromere
35
gap phase 2 (G2)
- prepare for the split of new replicated genome, fills gap between synthesis and beginning of mitosis)
- microtubules begin to recognize and form a spindle; chromosomes begin to condense
36
interphase
G1, S phase, and G2
37
mitosis
spindle apparatus assembles, binds to chromosomes, moves sister chromatids apart
- prophase, prometaphase, metaphase, anaphase, and telophase
38
cytokinesis
cytoplasm divides (2 daughter cells created)
- animal cells: microtubule spindle helps position contracting ring of actin (drawstring constricting motion to pinch cell in two)
- plant cells: plate forms between dividing cells
39
duration
shortest cycle = fruit fly cycle
- mature cells take much longer (human liver cells take a year)
40
G0 phase
between G1 and DNA replication; stage of cycle occupied by cells that are not actively dividing
41
after S phase
sister chromatids appear to share a centromere; molecular level shows DNA of centromere has already replicated (two complete DNA molecules)
42
cytoskeletal microtubules organization
- disassembled and rearranged to assemble machinery needed to move chromosomes to opposite poles of the cell
43
centrioles
(animal cells) microtubule organizing centers; replicate (one for each pole)
44
tubulin
globular protein subunit forming hollow cylinder of microtubules; used to construct mitotic spindle
45
prophase has begun when:
- chromosome condensation (from G2) reaches point where individual condensed chromosomes become visible with light microscope
- condensation continues through prophase
46
spindle apparatus
- forms during prophase; later separates sister chromatids
- replaces microtubule structure disassembled in G2 phase
47
centriole pair
(animal cells) - formed during G2 phase, being to move apart in prophase
- don't exist in plant cells
- axis of microtubules between them = spindle
48
microtubules
- polar, overlap at midcell
- kinetochore: attach to each chromosome at its kinetochore
49
aster
- a radial array of microtubules from centrioles towards plasma membrane
- probably braces centrioles for retraction of spindle
50
nuclear envelope breakdown
during formation of spindle apparatus
-endoplasmic reticulum absorbs all components
- orientation of microtubular spindle fibers determines plane in which cell will divide
51
prometaphase
- condensed chromosomes become attached to spindle by their kinetochores
52
microtubule attachment
- a second group of microtubules grow from poles to centromeres
- microtubules are captured by kinetochores on each pair of sister chromatids
- kinetochores of each sister chromatid connect to opposite poles of spindle (super critical)
53
movement of chromosomes
chromosomes are simultaneously being pulled toward each pole (leads to jerky motions) -> pulls all chromosomes to equator
54
force that moves chromosomes
(proposed)
1. assembly tails provide force to move chromosomes
2. motor proteins located at kinetochore and poles of cell pull on microtubules to provide force
both are probably a little at work
55
metaphase
alignment of chromosomes in the center of the cell
56
M phase plate
imaginary plate that indicates axis of future cell division
57
anaphase
- shortest phase; proteins holding sister chromatids together at centromeres are removed
- chromosomes are pulled rapidly toward poles (where kinetochores are attached)
- Anaphase A and B
58
anaphase A
- kinetochores are pulled towards poles (as microtubules shorten)
- tubulin subunits removed from kinetochore ends
59
anaphase B
- poles move apart as spindle fibers physically anchored to opposite poles slide past eachother
60
telophase
- spindle apparatus disassembles
- microtubules are broken down into tubulin monomers that can be used to make cytoskeletons of daughter cells
- nuclear envelope forms around each set of sister chromatids ("chromosomes" now because they are not attached to centromere)
- uncoil to permit gene expression
- reversal of prophase
61
cytokinesis
- involves cleavage of cell pinching in half
animal cells: actin filaments pinch and create a cleavage furrow around cell's circumference; deepens until it slices through the center
plant cells: too rigid for actin filaments - instead, assembles a cell plate that continues to grow out until it reaches and fuses with plasma membrane (dividing cell in 2)
- then cellulose gets laid on new membrane (new cell walls)
62
cell plate
structure that forms at equator of spindle during telophase in dividing cells of plants
63
middle lamella
space between daughter cells; impregnated with pectins
64
fungi + protists
nuclear membrane doesn't dissolve so all of mitosis occurs in nucleus
- nucleus then divides into 2 daughter nuclei
- cytokinesis: one nucleus to each daughter cell
65
cancer, disease
loss of control of cell cycle
66
checkpoints
DNA replication and separation of sister chromatids
67
discovery of maturation-promoting factor (MPF)
- a positive regulator of cell cycle progression in the cytoplasm of dividing cells (induced mitosis)
- discovered in frog oocytes
68
MPF
- activity varies during cell cycle: low at beginning of G2, rising through G2, peaking in mitosis
- enzymatic activity of MPF involved phosphorylation of proteins
69
cyclins
- proteins produced in synchrony with cell cycle
- discovered in sea-urchin embryo
70
cdc2
gene from fission yeast shown to be critical for passing boundaries (DNA synthesis and mitosis)
- encodes kinase protein
71
cyclin-dependent kinase (CdK)
a protein kinase enzyme that is only active when complexed with cyclin
- made MPF into mitosis promoting factor (from maturation)
- key drivers of cell cycle
72
G1/S checkpoint
- when the cell "decides" to divide
- yeast systems call it START
- animals call it the restriction (R) point
73
G2/M checkpoint
M-phase promoting factor (MPF) - super complex (stimulus for mitosis events)
74
spindle checkpoint
ensures all chromosomes are attached to spindle in prep for anaphase
75
phosphorylation
primary molecular mechanism of cell cycle control
- addition of phosphate group to amino acids (serine, threonine, and tyrosine)
76
first important CdK
found in fission yeast (Cdc2 or now Cdk1)
77
Cdc2 kinase
- controlled by phosphorylation
-phosphorylation activates Cdc2 at one point and inactivates at another
- full activation requires complex with cyclin and phosphorylation pattern
78
MPF function
M phase cyclin is necessary; activity is controlled by inhibitory phosphorylation
79
phosphatase
removes inhibitory phosphatesa
80
anaphase-promoting complex/cyclosome (APC/C)
triggers anaphase; acts by marking securin (protein) for destruction
- necessary for destruction of mitotic cyclins
- acts as a ubiquitin ligase
81
securin
acts as an inhibitor for separase which destroys cohesin (component called Scc1)
82
animal Cdks
multiple, more external signal response, more cyclins
83
yeast Cdks
singular
84
platelet derived growth factor
a growth molecule that can stimulate cell division in fibroblasts
