Chapter 11 Flashcards
What four events must occur for cell division
Reproductive Signal: initiate cell division
Replication: DNA replication and cell growth
Segregation: Distribute DNA into two cells
Cytokinesis: Separation of the new cells
What reproduction do prokaryotes use
binary fission
How are prokaryotes DNA usually found
How are eukaryotes DNA found
Pro: circular
Euk: linear
What two external factors initiate cell division
nutrient concentration
environmental conditions
What are interphases three subphases
G1: between mitosis and S phase
S phase: DNA replicates
G2: after S and before mitosis
Sister Chromatids definition
two identical molecules of DNA double helix that make up a chromosome
Why is DNA packaged tightly
So they do not separate and get tangled (spools of thread)
Sister chromatids are held together by what
COHESIN
Removal of what will have mitosis move forward
COHESIN
What are microtubules made out of?
two centrioles
microtubule organizing centers
spindle radiates outward
Mitosis is ________, but 5 stages have been named to characterize the process
continuous
What are the 5 stages in mitosis
prophase, prometaphase, metaphase, anaphase, telophase
What happens during prophase
chromosomes compact/coil becoming visible (packaging)
microtubules form between the centrosomes to make the spindle
kinetochores develop in the centromere regions
What happens during prometaphase
nuclear envelop breaks down
chromosomes attach to the kinetochore microtubules (extend from centrosomes to attach to chromosomes)
What happens during metaphase
chromosomes lined up at the middle of the cell (NOT PAIRED)
What happens during anaphase
sister chromatids separate and move to opposite ends of the spindle–referred to as “daughter” chromosomes
What causes the moval of chromosomes toward their sides
microtubules shortening
What happens during telophase
chromosomes finish moving and uncoil
spindle breaks down
the nuclear envelope is reformed
What motor proteins are the cause of the contraction of the ring
actin and myosin (in cytokinesis)
In cytokinesis, other organelles segregate _______; no special mechanism
randomly
What is the cause for plant cells to divide
New cell wall fuzing
Somatic cell definition
body cells not specialized for reproduction
Germ cell definition
make the gametes (haploid cells)
How do homologous pairs differ from one another
they have different allels
What is another word for tetrad
bivalent (4 chromatids)
Chromosome homologs are held together at ________ that forms between non-sister chromatids
chiasmata (crossing over)
The number of chromosomes at the equatorial plate in ________ is ____ the number of those in mitosis
Meiosis II, half
Where does independent assortment occur in meiosis
anaphase I (random segregation of homologous pairs)
What are polar bodies?
They are female gametes that do not turn into functional products/eggs
In mitosis what is the only stage in which there is not 46 chromosomes
anaphase
What are the main differences between mitosis and meiosis?
Mitosis: one somatic division, cytokinesis at the end of telophase, 2 cells produced, genetic clones
Meiosis: two cell divisions, cytokinesis at end of telophase I and II, 4 haploid cells produced, genetic recombination and diversity, chromatids do not separate during anaphase I
Crossing over definition and when does it occur
homologs cross over to exchange genetic material
prophase I
Independent assortment definition and when does it occur
homologs randomly line up during anaphase I
What are growth factors?
external chemical signals that stimulate cells to divide
Experiment: A cell in S phase contains an activator of DNA replication. A cell in S phase is combined with a cell in G1 phase. What are the results and conclusion?
The fuzed cell has two nuclei. The S phase cell produces a substance that diffuses to the G1 nucleus and activates DNA replication
Are CDKs always present in the cells
yes
A kinase is an enzyme that catalyzes _____________. Cdks are activated by binding to _______.
phosphorylation, cyclins (goes up and down in concentration during the cell cycle)
What are the two outcomes when a checkpoint is activated
repair or cell death
DNA damage activates protein kinases that ___________ p53.
phorphorylates
phosphorylated p53 acts as a ____________ that turns on genes that inhibit the cell cycle
transcription factor
___________ the cell cycle gives the cell time to repair the damaged DNA
inhibiting
When fixed p53 is ________ and processes move _____
shut down, on
p53 is only activated when _____
phosphorylated
Definition of oncogene and proto-oncogene
oncogene: mutated form of a gene that promotes cancer
proto-oncogene: the unaltered verision of an oncogene
oncogenes play a role in ______ cancer. Cancer ___ usually caused by _____, but by chemical agents instead
human, not, viruses
Definition of tumor suppressor
proteins whose normal activities inhibit cell division
Necrosis causes cells to swell and burst. This leads to _______ because cell contents are released to the extracellular environment
inflamation
Events of apoptosis:
cells are cut up, form blebs, surrounding cells eat the dead cells (this limits inflammation)
What are caspases
proteolytic (protein breakdown) enzymes, their role in controlling cell death and inflammation
The removal of growth factors equals
cell death
Mutational activated RAS is an example of
an oncogene
A cell dies in apoptosis because
it is programmed to die
A mutation acquired by a bacterium will very likely be inherited by all daughter cells
true
What DNA sequences are most alike
a pair of sister chromatids
A skin cell in G2 of interphase has _______ as much DNA as it had in G1
twice
What would happen during cell division if the cell was deficient in actin?
the cell would not divide
Synapsis occurs during
prophase I of meiosis
