mitosis Flashcards
is mitosis somatic or sexual?
somatic
is meiosis somatic or sexual?
sexual
what is the first step of mitosis/meiosis?
replication
who discovered DNA?
watson, crick, franklin
dna replication
- results in new cells
- happens in nucleus (DNA “unzips” and gets copied –> RNA)
- after replication: 2 identical copies
- semi-conservative replication
semi-conservative replication
1 parent strand + 1 new strand
base pairing in DNA
adenine (A) + thymine (T)
guanine (G) + cytosine (C)
DNA copying
- starts with RNA primer
- 5’ to 3’
- done with help of enzyme (DNA polymerase)
- “mismatch repair” - checks for and corrects mistakes
where does DNA copying start?
origin of replication
noncoding DNA sequences
transcription/translation regulators
origins of DNA replication
centromeres
telomeres
what are telomeres?
to protect genes of eukaryotic chromosomes, special noncoding DNA sequences evolved at end of strands called telomeres
describe telomeres?
- no genes
- protect genes from eroding at ends
- shrink each time cell divides
- possibly connected to aging process
telomerase
catalyzes lengthening of telomeres in eukaryotic germ cells
phase of life of cell
G1, S, G2, mitosis
interphase
G1, S, G2
G1
beginning of cell’s life, centrioles start dividing, cytokinesis, cells grow to full size, transcription/translation, DNA in single strands
S
only DNA replication, 2 double stranded DNA, diploid/haploid cells, no more RNA made (leftovers used for repairs), centrosomes and centrioles replicating, CANNOT DIVIDE WITHOUT THIS
G2
nucleus well defined with membrane, centrosomes present (2 centrioles), DNA fully duplicated but in chromatin form, new RNA transcribing for spindle fibers, leftover RNA for repairs
what is the most important checkpoint of cell life?
G1
centrosome
- area for production/organizing microtubules
- plants: centrosome, no centrioles
- animals: 2 centrosomes, each have 2 centrioles, and move to opposite sides of cell
what cells are always in G0?
nerve, muscle, liver cells can be activated to come out of G)
do cancerous cells obey checkpoint control?
no
what are checkpoints controlled by?
regulatory proteins (p53)
how does p53 stop cancer?
- can pause cell cycle, initiate cell DNA repair
- if can’t fix DNA, will induce cell death (apoptosis)
apoptosis
programmed cell death
what are the 5 stages of mitosis?
prophase, prometaphase, metaphase, anaphase, telophase
prophase/prometaphase
DNA condenses, spindle fibers form, centrosomes move to pole, breakdown of nuclear membrane
metaphase
chromosomes line up in the middle of the cell, centrioles completely opposites, kinetochore attaches to spindle fiber
anaphase
sister chromatids seperate, spindle fibers shorten,
telophase
daughter nuclei begin to form, nuclear membrane begins to form, cytokinesis begins (cleavage furrow splits cell into 2 daughter cells), cleavage furrow caused by actin filaments
what happens during telophase for plants?
cell wall will form
