Chapter 16: Cell Cycle Mitosis And Meiosis Flashcards
requirements for cell growth
growth and metabolism- cell mass must increase
DNA replication- DNA is duplicated so there are 2 exact copies of each chromosome
mitosis and cytokinesis- contents of cell are divided so each cell gets identical amount of genetic material
mitosis is ___ division
cytokinesis is ___ division
nuclear
cell/cytoplasm
phases of the cell cycle
G1- gap between M and S, start
S - DNA replication, centrosome is replicated
G2 - gap between S and M
M- mitosis and cytokinesis
phases in interphase
G1, S, G2
cytokinesis
division of the cytoplasm (there are 2 cells now)
Mitosis
division of the nucleus
what happens when cells pass a point in G1 called start or ____?
restriction point
they are committed to going through the rest of the cell cycle
what happens to cells that don’t pass through start?
may enter G0, a resting phase, until conditions change
cells spend a lot of time in which phase?
G1
chromatid number
G1: each chromosome has ___ chromatid
G2: each chromosome has ___ chromatid
1
2
key transition points in the cell cycle are
most important?
G1 checkpoint: restriction point (start)- most important
G2 Checkpoint
Metaphase Checkpoint
G1 checkpoint
regulates passage beyond start and entry into S
main regulatory checkpoint. Once a cell passes start if is committed to dividing
G1 checkpoint is influenced by
growth factors- like hormone, promotes growth
nutrients- have enough nutrients to support 2 cells
cell size- is it big enough to split into 2?
DNA damage- don’t want to replicate cells with damage
G2 checkpoint
regulates entry into M
G2 checkpoint influenced by
cell size
DNA damage
DNA replication- is replication complete?
Metaphase checkpoint
cells checks to make sure chromatids are attached to spindle. Mitosis is delayed until all chromatids can be properly attached
past the metaphase checkpoints, cells are
committed to dividing the chromosomes up between 2 daughter cells
Metaphase Checkpoint is influenced by
chromosome attachments to spindle
function of mitosis
to produce a duplicate of the parent cell
all growing cells carry out
2n cells->
1n cells->
mitosis
2 new 2n cells (diploid)
2 new 1n cells (plants and fungi, not humans) (haploid)
when does Mitosis occur
M phase
diploid organisms have _ of each chromosome, ___ from each parent
2
1
sister chromatid
Same genes and exactly the same alleles
homologous chromosomes
same genes, may have different alleles
nonsister chromatids
same genes, may have different alleles
function is to produce 2 identical cells
each cell is ___ to the parent cell
each cell has ____ dna
mitosis
identical
exactly the same
chromatin
complex of DNA and proteins
DNA is double stranded and made of nucleotides
50% is protein (histones and nonhistones)
extended losses lacked uncondensed for of DNA
form
found where
chromatin
beads on a string
interphase (actively growing)
form of DNA accessible to enzymes
chromatin
most tightly packed condensed form of DNA
shape
visible
chromosome
X shaped chromosome
only mitosis and meiosis
chromosome need __ types of sequences and they are
3
ORI- original of replication
Centromere- connect to the spindle fibers and sister chromatids
telomere- ends of chromosomes
kinetochore
protein disc
one end attaches to centromere of chromosome
one end attaches to kinetochore microtubules- spindle
homologous chromosomes
same genes in same order
one from each parent
same six and shape
may have different alleles
heterologous chromosomes
different chromosomes
contains different genes
each chromatid is ___ of DNA
one molecule
one half of the x - the other half is identical
haploid
1N
1 of each chromosome
human gametes
diploid
2N
2 of each kind of chromosome
human somatic cells
one complete set came from mom and dad
N=
of heterologous chromosomes
gene
region of DNA that codes for an RNA or protein (trait)
allele
different form of a gene/ trait
a vs A
you can have more than two forms of alleles
shape of genes and alleles
seed shape
smooth or wrinkled
count __ not ___ to determine haploid or diploid
chromosomes
chromatids
chromosomes can have 1 or 2 chromatids in what type of cells
Haploid or diploid
a chromosome has its own
centromere
what division is not in humans?
1N -> 2 new 1n cells
DNA is replicated in the __ phase so each chromosome has ___ chromatids
S
2
centrosome was replicated in _ phase
S
phases of mitosis
prophase, prometaphase, metaphase, anaphase, telophase
function of interphase
cell growth and metabolism
prophase
chromatin condenses into chromosomes
chromosome has 2 chromatids
nucleosus disappears
spindle forms
prometaphase
nuclear membrane breaks down
chromosomes attach to spindle
microtubules attach to chromosomes at the
kinetochore
metaphase
chromosomes line up in the middle of the cell
1 chromosome per spindle fiber
anaphase a
chromosomes split
each chromatid is now called a chromosome (has its own centromere)
chromosomes move to opposite poles
anaphase b
cell elongates in preparation for cell division =cytokinesis
spindle fibers (polar microtubules) push against each other
telophase
reverse of prohase
nuclear membrane reforms
chromosomes decondense, go back to chromatin
spindle fibers breaks down
nucleolus reforms
cytokinesis- cell division
Mitosis result of telopahse and cytokinesis
2 identical cells, each chromosome has 1 chromatid
C=
number of chromatids per cell (dna content)
result of mitosis
____ cells
each cell has ___ chromosomes
each cell has ___ dna
2 identical
same number
exactly the same- same alleles
human gametes ____ divide
never
diploid cells: 2N cells->
haploid cells: 1N cells->
2 2N cells
2 1N cells
reduction division =
meiosis
Meoisis
G1
G2
end of meiosis 1
and of meiosis 2
2N
2N
1N
1N
meiosis function
to make cells that have half the number of chromosomes as the parent cell
meiosis: daughter cells have ___ as parent cell
half the number of chromosomes
meiosis: each daughter cell has the same number of chromosomes but the DNA In each cell is
different- different alleles
meiosis: only in special reproductive cells that produce
gametes
sperm and eggs (both 1N)
diploid organisms have __ of each chromosome, _ from each parent
2
1
meiosis has __ rounds of cell division
Meiosis 1: ___ separates
Meiosis 2: ___ separates
2
homologous chromosomes
sister chromatids
what happens in meiosis 1
homologous chromosomes separate and go to different cells
what happens in meiosis 2
sister chromatids separate and go to different cells
interphase
dna is in ___ form
____ surrounds the dna
___ have replicated
chromatin
nuclear membrane
centromeres
prophase 1
nuclear membrane breaks down
spindle forms
chromatin condenses into chromosomes
homologous chromosomes pair up (only happens in prophase in meiosis
when does crossing over of nonsister chromatids of homologous chromosomes occur
may occur in prophase 1
metaphase 1
homologous chromosome pairs attach to spindle
homologous chromosome pairs line up in the middle of the cell (line up randomly)
anaphase 1
homologous chromosomes pairs and separate
each chromosome goes to opposite pole
cell elongates and cytokinesis begins
if a chromatid has its own centromere and it is called
Chromosome
telophase 1
nucleus reforms
chromosomes decondense into chromatin
spindle disappears
opposite of prophase 1
result of meoisis 1
each cell is 1N- has 1 copy of each chromosome
each chromosome has 2 chromatids
dna in each cell is not identical
in meiosis 2 cells have _ chromosomes from
1
each homologous pair
prophase 2
nucleus breaks down
spindle forms
chromatin condenses into chromosomes
metaphase 2
each chromosome attaches to the spindle
chromosomes line up in the middle of the cell
anaphase 2
chromatids are pulled apart
each chromatid= chromosomes
each chromosome goes to the opposite pole
telophase 2
nucleus reforms
spindle disappears
chromosomes decondense into chromatin
telophase 2 and cytokinesis
cytokinesis = cell division is complete
4 haploid cells
telophase 1 and cytokinesis
cytokinesis- cell division is complete
result of meiosis 2
each cell has 1 of each chromosome- 1N
each chromosome has 1 chromatid
the dna in each cell has different gene combinations- different alleles
independent assortment
different products of meiosis are made depending on how the chromosome pairs line up during metaphase 1
each chromosome assorts independently: maternal and paternal chromosomes line up
randomly
significance of independent assortment
equation
a large number of gene combinations are possible
total combinations possible - 2^n
n- unique chromosomes
recombination = crossing over
chromosomes
chromatids
In prophase 1 homologous chromosomes line up so there are 4 chromatids lined up together
Nonsister chromatids exchange part of their dna : dna breaks and rejoins creatin new gene combinations
crossing over is ___
the farther apart 2 genes are ___
common
the more crossovers will occur between them
significance : crossing over produces
new gene combinations
mitosis vs meiosis functions
to produce 2 identical cells
to produce cells that have half the number of chromosomes
mitosis vs meiosis which cells
any cells
only in reproductive ells
mitosis vs meiosis starting cells
can be 2N or 1N - each chromosome has 2 chromatids
only in 2N cells - each chromosome has 2 chromatids
in multicellular 1N organisms, not humans
mitosis
mitosis vs meiosis prophase
see individual chromosomes
1- homologous chromosomes pair up
mitosis vs meiosis metaphase
individual chromosomes attach to the spindle
1- chromosome pairs attach to the spindle (2 on each spindle)
mitosis vs meiosis anaphase
sister chromatids separate
homologous chromosomes separate
mitosis vs meiosis telophase
2 identical cells are made - can be 2N or 1N (2 of each chromosome, 1 chromatid/ chromosome)
1- 2 different 1N cells are made (1 of each chromosome, 2 chromatids/ chromosome
2- 4 different 1N cells ( 1 of each chromosome, 1 chromatid/ chromosome
is crossing over common?
yes
