What did the brother cell say when the sister cell stepped on him? Mitosis.
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Transcript of What did the brother cell say when the sister cell stepped on him? Mitosis.
Cells come from ________________ cells This statement tells us that cells reproduce and the
way they do this is through cell ________________ (p.218 Figure 12.1).
Roles in Life: _________________
Amoeba: divides and forms a duplicate Plants: some can divide and form offspring Sexual Reproduction: organisms develop from a
single cell (zygote) Renewal and Repair
Dying, ________, or torn cells. Cell Cycle: life of a cell from the time it is formed
from a dividing _________ cell until its own division into two cells.
Cell division is ________ of the cell cycle
PRE-EXISTING
DIVISION
REPRODUCTION
WORN
PARENT
PART
Cell Division: results in genetically ________________ daughter cellsOrganization of Genetic Material (______)
__________: the entire amount of genetic material (DNA) Length of DNA is very large (2 m of DNA in
human cells: __________ greater than a cell’s diameter). This DNA must be copied _________ division.
The reason DNA replication is not a problem is because DNA is packed into chromosomes made of ________________ (DNA wrapped around ___________)
Each species has a certain number of _________________ in each cell nucleus.
IDENTICAL
DNA
GENOME
250,000 xBEFORE
CHROMATIN PROTEINS
CHROMOSOMES
Two types of cells:___________ (body) cells: all cells that are not
reproductive (sex) cells. Ex: Humans have ___ chromosomes (2 sets of
23, one from each parent).____________ (sex/reproductive cells): sperm and
egg cellsEx. Human gametes have half as many
chromosomes as somatic cells: one set of ______ chromosomes.
http://www.genebase.com/learning/article/30
SOMATIC
46
GAMETES
23
Distribution of Chromosomes During Cell Division
When not in division, each chromosome is in the form of chromatin, but ________________ (coils) to chromosomes after duplication so they are __________.
Each duplicated chromosome has two ___________ chromatidsTwo chromatids, each containing an identical DNA
molecule are attached at the ________________.
http://en.wikipedia.org/wiki/File:Major_events_in_mitosis.svg
CONDENSESVISIBLE
SISTER
CENTROMERE
In cell division, the two sister ________________separate into two nuclei, one at each end of the cell.
Once the sister chromatids separate, they are considered individual __________________. Each nucleus has a group of chromosomes ________________to the original.
Mitosis: division of the _____________ (chromosomes split into 2 identical sets)
Cytokinesis: division of the ________________ (division of the two nuclei into two cells)Example:
______ (46 chromosomes): 23 chromosomes (______) + 23 chromosomes (______)
Mitosis and ________________produce the trillions of somatic cells that make up human bodies and continue to generate cells.
Meiosis: yields _________________ daughter cells that have only one set of chromosomes. Only occurs with __________. This will be covered in Ch. 13.
CHROMATIDS
CHROMOSOMESIDENTICAL
NUCLEUS
CYTOPLASM
BABY MOMDAD
CYTOKINESIS
NON-IDENTICALGAMETES
Phases of the Cell Cycle________________ (M) Phase (when division occurs)-
___________ part of the cell cycle that includes:_______________________. cell cycle animation
http://scientopia.org/blogs/scicurious/2010/05/31/cell-cycle-p21-depression-and-neurogenesis-and-in-the-hippocampus/
MITOTICSHORTEST
MITOSIS
CYTOKINESIS
Interphase (in ____________ cell divisions)- accounts for ____% of the cell cycleWhere the cell _________ and copies its chromosomes to prepare for
divisionThree Subphases:
____ Phase (“first gap)- protein and ________________ (mitochondria and chloroplast) synthesis (double cell size)
S Phase (“________________”)-___________________ are duplicated (DNA synthesis only in S phase)
___ Phase (second gap”)- continued growthSequence (remember):
________________ (G1, S, G2), M phase
mitosis: prophase, ___________________, metaphase, anaphase, telophase
cytokinesis
BETWEEN 90
GROWS
G1 ORGANELLE
SYNTHESIS CHROMOSOMES
G2
INTERPHASE
PROMETAPHASE
Mitotic SpindleInvolved in many events of mitosis and begins to
form in the ________________ during prophase.Consists of fibers (__________________ and proteins).The spindle microtubles lengthen by including
more subunits of ________________.
http://www2.estrellamountain.edu/faculty/farabee/biobk/biobookmito.html#Mitosis
CYTOPLASM
MICROTUBULES
TUBULIN
Mitotic Spindle Assembly:Starts at the ________________
centrosome- a nonmembranous organelle that organizing the cell’s microtubules during the cell cycle
In animal cells, two ________________are located at the center of the centrosome but are not
essential to cell division. Ex: ________ don’t have centrioles
________________is when the centrosome replicates to form two which stay together near the nucleus.
The two move apart during prophase and __________________ as spindle microtubules grow from them.
At the end of prometaphase, the two centrosomes are on ____________ ends of the cell. An _________ which looks like a sun burst of microtubules from each centrosome.
CENTROSOME
CENTRIOLES
PLANTS
INTERPHASE
PROMETAPHASE
OPPOSITE ASTER
ChromosomesEach chromatid of a chromosome has a
________________-a structure of proteins that appear at specific sections of chromosomes at the centromere.Kinetochores are where microtubules connect to
pull sister ________________ apartThe centrosome’s two kinetochores face in
____________ directions.During prometaphase, some of the spindle
microtubules attach and are called kinetochore microtubules.
The next event is like a ________________ that ends in a draw: the chromosomes move and finally stop when the centromeres of all the duplicated chromosomes are on a plane __________ between the spindle’s two poles. This plane is the metaphase _______.
At this time there are some microtubules that are not attached to kinetochores but overlap and interact with other _______________________ microtubles.
KINETOCHORE
CHROMATIDSOPPOSITE
TUG OF WAR
MIDWAYPLANE
NONKINETOCHORE
Moving apartStarts when the proteins holding the sister
chromatids become ________________ allowing the sister chromatids to become separate chromosomes.
These chromatids will move toward opposite sides of the cell.
The region of overlap between the microtubules is reduced as ATP is used to push the microtubules apart. This ________________ the cell.
At the end of anaphase, duplicate groups of chromosomes arrive at ____________ ends of the now longer parent cell.
During telophase, nuclei reform and cytokinesis begins and the spindle disassembles.
INACTIVE
ELONGATES
OPPOSITE
Summary of the Cell Cycle mitosis animationInterphase
Nuclear envelope is ________________The nucleus has at least one ________________Two centrosomes have formed and will be next to
each other (animal cells will have ______________).In the nucleus, ________________ is seen
http://humanbiorevision.tumblr.com/post/2845616247/interphase
PRESENT
NUCLEOLI
CHROMATINCENTRIOLES
ProphaseChromatin has condensed into __________________.Duplicated chromosomes appear as identical sister
chromatids joined at _________________.Nucleoli disappear.Mitotic spindle forms as centrosomes move apart.
as microtubules emerge from the centrosomes, _________ can also be seen.
http://humanbiorevision.tumblr.com/post/2845688920/prophase
CHROMOSOMES
CENTROMERES
ASTERS
PrometaphaseNuclear envelope ___________ down.Chromosomes become more ________________.Microtubules from the mitotic spindle _________
even more.Each sister chromatid has a ________________
located at the centromere.Kinetochore microtubule: ________ chromosomesNonkinetochore microtubules interact with other
nonkinetochore microtubules (from _____________ side).
http://www.stanford.edu/group/hopes/cgi-bin/drupal/node/3401
BREAKS
CONDENSED
EXTEND
KINETOCHORE
MOVE
OPPOSITE
Metaphase (longest stage of mitosis)Centrosomes are at ________________ poles of cellChromosomes line up in the middle of the cell
(metaphase __________)The kinetochore of sister chromatids are connected
to microtubules from the opposite pole.
http://humanbiorevision.tumblr.com/post/2845819608/metaphase
OPPOSITE
PLANE
Anaphase- shortest stage of mitosis____________ protein cleaved allowing sister
chromatids to move apart allowing each to become a separate chromosome.
The two chromosomes move toward opposite ends of the cell as kinetochore microtubules ___________.
The nonkinetochore microtubules ____________ which elongate the cell
At the end, the two ends of the cell have an _________ amount of complete chromosomes.
http://humanbiorevision.tumblr.com/post/2845909550/anaphase
COHESION
SHORTEN
LENGTHEN
EQUAL
Telophase______ nuclei form in the cell.Nuclear envelopes form from parent cell’s
nuclear envelope ____________.________________ reappearChromosomes become less condense
(________________)Mitosis is complete (2 complete, ___________
nuclei)
http://humanbiorevision.tumblr.com/post/2845943979/telophase
TWO
FRAGMENTS
NUCLEOLI
CHROMATIN
IDENTICAL
Cytokinesis Division of cytoplasm usually starts in late
_____________. Two ________________ cells appear shortly after
mitosis ends. Animal cells form a cleavage ___________ which
pinches the cell (cytoplasm) in two. Plant cells form a ________________ which divides
the cell (cytoplasm) in two.
TELOPHASE
DAUGHTER
FURROW
PLATE
Cytokinesis in DetailCleavage Furrow (animals)
First sign is a shallow groove in the cell surface near the old metaphase plate.
It deepens until the parent cell is pinched in two producing two separated cells with their own organelles, etc.
http://www.monteweston.com/Biology/Preeti.htmlhttp://www.tutorvista.com/biology/cytokinesis-pictures
Cell Plate (plants)Cell wall materials carried in the ___________ collect
in the cell plate as it grows. The cell plate grows until its membrane _______ with the plasma membrane along the perimeter of the cell.
Two daughter cells result, each with its own plasma membrane and cell ______.
http://www.phschool.com/science/biology_place/biocoach/mitosisisg/cytokin.html
VESICLES
FUSES
WALL
Binary Fission ________________ reproduction of single-celled
eukaryotes, such as the amoeba includes mitosis and occurs by a type of cell division called binary fission, meaning "division in half.'
Prokaryotes (bacteria and archaea) also reproduce by binary fission, but the prokaryotic process does not involve ________________.
ASEXUAL
MITOSIS
Evolution of Mitosis Hypothesis: mitosis had its origins in
________________ prokaryotic mechanisms of cell reproduction.
Support: Some of the proteins involved in bacterial binary fission are related to eukaryotic ________________ that function in mitosis.
As eukaryotes evolved, with larger genomes and nuclear envelopes, binary fission, seen today in bacteria, somehow led to ________________.
Possible hypothesis for the stepwise evolution of mitosis. Figure 12.12 p.237
SIMPLER
PROTEINS
MITOSIS
What controls the cell cycle? Cell Cycle is controlled by specific ________________
molecules in the cytoplasm. Experiment:
Two cells in different phases of the cell cycle were fused to form a single cell with two nuclei.
If one of the original cells was in the S phase and the other was in G1, the G1 nucleus immediately entered the ___ phase
Similarly, if a cell undergoing mitosis (M phase) was fused with another cell in any stage of its cell cycle, even G1, the second nucleus immediately entered ___________, with condensation of the chromatin and formation of a mitotic spindle
SIGNALING
S
MITOSIS
Cell Cycle Control System Definition: a ________________ operating set of
molecules in the cell that both triggers and coordinates key events in the cell cycle.
Checkpoint- a control point where stop and go-ahead signals regulate the cycle.
Animal cells usually have built-in stop signals that ________ the cell cycle at checkpoints until overridden by go-ahead signals.
Signals report whether cellular processes that should have occurred have occurred and whether or not the cell cycle should ________________.
Three major ________________ are found in the G1,G2, and M phases
CYCLICALLY
PAUSE
PROCEED
CHECKPOINTS
For many cells, the G1 checkpoint ("_______________ point") in mammalian cells, seems to be the most important: if a cell receives a go-ahead signal at the G1 checkpoint, it will usually ________ the cell cycle.
If a go-ahead signal is not given, it will exit the cycle, switching into a ________________ state called the G0 (G ZERO) phase. (most cells in G0 phase).
Example: Think a ____________ machine. Timing device: the cell cycle control
system works on its own, according to a built-in clock.
Internal and External ______________: Washers have an internal sensor that detects when the water is present and
external adjustment such as pressing the start button.
RESTRICTION
FINISH
NONDIVIDING
WASHING
REGULATION
______________________ molecules: Protein Kinases and Cyclins
Protein kinases- enzymes that activate or inactivate other proteins by _______________________ them
Protein kinases- give the go-ahead signals at the G1 and G2 ________________.
Many kinases that drive the cell cycle are present at a ________________ concentration in the growing cell, but are usually in an ___________ form.
To be active, such a kinase must be attached to a ________________ (gets its name from its cyclically fluctuating concentration)
CELL CYCLE CONTROL
PHOSPHORYLATING
CHECKPOINTS
CONSTANTINACTIVE
CYCLIN
Because of this requirement, these kinases are called cyclin-dependent kinases, or Cdks. The activity of a Cdk rises and falls with changes in the __________________ of its cyclin partner.
Figure 12.16a shows the fluctuating activity of MPF, the cyclin-Cdk complex that was discovered first (in frog eggs).
Peaks of MPF activity correspond to peaks of __________ concentration The cyc1in level rises during the S and G1 phases
The initials MPF stand for "________________ -promoting factor”; but we can think of MPF as "M-phase-promoting factor” because it triggers cell’s passage through G2 checkpoint to M phase.
CONCENTRATION
CYCLIN
MATURATION
Internal and External Signals _______________ Signal at the M phase checkpoint:
__________________ In ______________, sister chromatids do not
_______________ until all the chromosomes are properly attached to the spindle at the metaphase plate.
It is the __________________ that send a signal that delays anaphase.
When the kinetochores of all chromosomes are ______________, the sister chromatids can _____________.
This allows daughter cells to have an ____________ amount of chromosomes.
INTERNALANAPHASE
ANAPHASESEPARATE
KINETOCHORES
ATTACHED SEPARATE
EQUAL
_______________ Factors that limit cell division Cells will fail to _____________ if an essential
nutrient is left out of the culture. ______________ factors are needed for division.
Growth factors are ______________ released by cells that stimulate cell division.
Platelet-derived growth factor (______) p. 231 Figure 12.17
Made by blood cells called ________________. Demonstrates that PDGF is _____________ for the
division of fibroblasts in culture. PDGF sends a signal that allows cells to pass
______ checkpoint to divide.
EXTERNAL
DIVIDE
GROWTH
PROTEINS
PDGF
PLATELETS
REQUIRED
G1
Density-dependent _____________ (effect of an external physical factor)
Phenomena where crowded cells stop ____________ (p. 232: Figure 12.18a)
Cells normally divide until they form a __________ layer on the surface of the container then they ________ dividing.
If cells are __________, the cells around the empty space __________ until the space is filled.
It was first thought that ____________ contact sent a signal to stop division but growth factors has a larger effect:
When a cell population reaches a certain ____________, the nutrients available are insufficient so cell division stops.
Anchorage dependence- to divide, cells must be ____________ to a (stable) surface such as a dish or extracellular matrix of a tissue.
INHIBITION
DIVIDING
SINGLESTOP
REMOVEDDIVIDE
PHYSICAL
DENSITY
ATTACHED
Loss of Cell Cycle Control in Cancer Cells Cancer cells do _______ follow the regulations/signals
like normal cells and divide excessively and invade other tissues.
Cancer cells lack ____________________________________, anchorage dependence, and do not stop dividing when growth factors are depleted. Example: p. 233 Figure 12.19
Hypotheses why: Cancer cells do not need growth factors. Cancer cells make their own growth factors. Cancer cells can display growth factor’s signal
despite the lack of growth factors. Abnormal cell cycle control system. (more in Ch.
19)
NOT
DENSITY-DEPENDENT INHIBITION
Other differences between normal and cancer cells When/if cancer cells stop division, it is
____________ instead of at checkpoints. Cancer cells can divide _______________ if they
have a continual supply of nutrients. Ex. HeLa cells
RANDOM
INDEFINITELY
Behavior of Cancer CellsTransformation (change in DNA) occurs when a single
cell in a tissue ______________ from a normal cell to a cancer cell.
The __________ system can destroy it but if the cancer cell avoids destruction, it can continue to grow and form a tumor- a mass of abnormal cells within a “normal” tissue.________________ tumor- abnormal cells remain at the
original siteNo serious problems and can be removed by
surgery._______________ tumor- abnormal cells invasive enough
to impair the functions of one or more organs.Someone with a malignant tumor is said to have
cancer.
TRANSFORMS
IMMUNE
BENIGN
MALIGNANT
Malignant tumors: may have unusual numbers of ___________________ ________________ may be disabled- may not
function in a constructive way May lose or destroy attachments to neighboring
cells and the ECM to spread into nearby tissues. Can also secrete molecules that cause
___________________to grow toward the tumor. Tumor cells can separate and enter the blood
vessels to travel to other parts of the body where they can form a new tumor.
________________- spread of cancer cells to locations away form original site.
CHROMOSOMESMETABOLISM
BLOOD VESSELS
METASTASIS
Treatment: Localized tumors may be treated with high-energy
_________________ Radiation damages _______ in cancer cells much more
than normal cells because cancer cells have lost the ability to repair such damage.
____________________- drugs toxic to actively dividing cells are given through the circulatory system to treat suspected metastatic tumors.
Chemotherapeutic drugs interfere with steps of the cell cycle
Example: Taxol freezes the mitotic spindle which stops actively dividing cells from going beyond metaphase.
Side effects of chemotherapy are from the drug’s effects on normal cells.
Nausea is caused by effects on intestinal cells, hair loss on follicle cells, and increased susceptibility to infection on immune system cells.
RADIATIONDNA
CHEMOTHERAPY
Introduction Heredity or _________________- transmission of
traits from one generation to the next Heredity passes down inherited similarities and
genetic _________________. _________________- study of heredity and hereditary
variation.
INHERITANCE
VARIATION
GENETICS
Acquisition of Genes Parents pass down coded information in the form
of _________ to their offspring. It is the genes that account for family
______________ such as eye color, freckles, etc. Our genes program the specific __________ that
emerge as we develop from fertilized eggs into adults.
In order to pass down hereditary traits, ________ must first be replicated.
In animals, ___________ (reproductive cells) are what pass genes from one generation to the next.
_________________: the uniting of male and female gametes (sperm and egg) which passes genes of both parents to the ____________.
GENESSIMILARITIES
TRAITS
DNA
GAMETES
FERTILIZATION
OFFSPRING
_________________ consist of a single long DNA coiled with proteins.
__________ genes are located on a chromosome ________: a gene’s specific location along the
chromosome Asexual Reproduction (p. 239 fig 13.2)
Definition: organisms produce offspring that are _________________to them (all the genes are passed).
Offspring are all identical: ___________. Example: Hydra- can reproduce by budding
(_________)
CHROMOSOMES
MANY
LOCUS
IDENTICALCLONES
MITOSIS
Sexual ReproductionDefinition: two parents give rise to offspring that
have unique _________________ of genes inherited from the parents.
Offspring are genetically _________________from siblings and parents.
Allows genetic _____________.Why different than asexual reproduction?
Behavior of _________________ during the gamete life cycle.
COMBINATIONS
DIFFERENT
VARIATION
CHROMOSOMES
Sexual Life Cycles Life cycle- generation to generation occurrences in the reproductive history of
an organism from _______________ to having its own offspring. _________________- display of 46 human chromosomes from a single cell
in mitosis. Chromosomes are arranged in __________, according to size and
structure. ___________________ chromosomes (_________________): the two
chromosomes have the same length, centromere position, staining pattern. Both carry genes that control the same ____________.
Ex. Eye color gene exists at the __________ locus as on the other chromosome (genes may not be identical i.e. freckles)
Karyotyping can be done using cells collected by chorionic villus (placental tissue) sampling or ____________________ for pre-natal diagnosis of chromosome _________________.
Used to _______ for chromosome abnormalities and genetic disorders Controversy….
BIRTHKARYOTYPE
PAIRS
HOMOLOGOUS SIMILAR
TRAITSAME
AMNIOCENTESISABNORMALITIES
TEST
Sex chromosomes- X and Y chromosomes determine an individual’s _____. All other chromosomes are called _________________.
XX- female XY-male X is much ________ than Y. Only small parts of X
and Y are ________________. Most genes on the X do not have _________________ on the Y and vice versa.
SEXAUTOSOMES
LARGERHOMOLOGOUSCOUNTERPARTS
Why do we have homologous pairs of chromosomes? We inherit one from each ____________. Total: 23 (mom) +
23 (dad) n- the number of chromosomes in a __________ set. _________ cell- any cell with two chromosome sets and
also a diploid number of chromosomes (2n) Example: Humans- Diploid number is 46 and _____ = 46
Haploid cell- any cell with a _________ chromosome set and also a haploid number of chromosomes (n)
Example: Humans- Haploid number is 23 and n = 23 The 23 consist of 22 _________________ and a single sex
chromosome. Unfertilized egg cell (________) contains an X
chromosome while sperm cell can contain _________________ chromosome.
Figure 13.4
PARENT
SINGLE
DIPLOID
2nSINGLE
AUTOSOMES
OVUM
X OR Y
Human Life Cycle Starts when a haploid sperm cell from the father
_______ with the haploid ovum cell from the mother.
The fusing of the gametes ends in fertilization, the fusion of their __________.
The fertilized egg, _______________, is diploid because of the fusion of the two ______________ sets.
As the zygote develops into a mature adult, ____________ generates all the somatic cells by passing both chromosome sets and all the genes.
FUSES
NUCLEI
ZYGOTEHAPLOID
MITOSIS
The only human cells not produced by mitosis are the __________ which generate in the gonads (ovaries in females and testes in males).
Why not divide by mitosis ____________________________________________
Gametes use ____________: a type of cell division which _________________ the number of sets of chromosomes from two to ______ in gametes to prepare for the doubling during fertilization. (_____________ division from diploid to haploid)
GAMETES
MITOSIS PRODUCES IDENTICAL CELLS
MEIOSISHALVES
ONEREDUCTION
Meiosis summary Meiosis overview Before division, chromosomes are _________________
(_________________). After chromosome replication, there are two
_________________ cell divisions: Meiosis I and Meiosis II. Results in ___________ daughter cells instead of two like
mitosis. Each daughter cell has ___________ as many
chromosomes. Review:
Sister chromatids- two copies of one chromosome attached at the centromere and make up one duplicated _________________
Homologous pairs are individual chromosomes that were inherited from _________________ parents and are not _________________. They are similar (same gene location) but not identical.
REPLICATEDCOPIED
CONSECUTIVE
FOUR
HALF
CHROMOSOME
DIFFERENTCONNECTED
Steps of Meiosis Interphase
Chromosomes replicated during the S phase but remain _________________.
Each replicated chromosome consists of two identical sister _________________ connected at the centromere.
_________________ replicates, resulting in two.
UNCONDENSED
CHROMATIDS
CENTROSOME
Meiosis I Prophase I (usually occupies >_____% of time in
meiosis) Chromosomes begin to _________________. Homologous chromosomes pair along lengths
and are lined so genes are _________________. ___________________occurs: DNA molecules in
non-sister chromatids break at corresponding places and ____________ each other (switch locations).
______________ occurs where a synaptonemal complex forms between homologous chromosomes which holds the chromosomes together tightly.
The synaptonemal complex breaks down in late prophase and each chromosome pair becomes visible as a ______________ (a group of four chromosomes)
90
CONDENSE
ALIGNEDCROSSING OVER
REPLACESYNAPSIS
TETRAD
(Prophase I continued)Each tetrad has at least one _________________
(plural: chiasmata)- a criss-crossed region where crossing over occurred. The chiasmata hold the homologous chromosomes _________________ until anaphase I.
Just like in mitosis, _______________ move apart, spindle microtubules form, the nuclear envelope breaks down, and the nucleoli disappear.
In late prophase I, the kinetochores of each homologous chromosome attach to _________________ from the poles, then they are moved towards the _________________ plate.
CHIASMA
TOGETHERCENTROSOMES
MICROTUBULESMETAPHASE
Metaphase I The pairs of homologous chromosomes
(__________) are lined up on the metaphase plate with one chromosome of each pair facing each pole.
Both chromatids of a _________________ are attached to kinectochore microtubules from one pole; the other homologue to the microtubules from the opposite pole.
TETRAD
HOMOLOGUE
Anaphase I Chromosomes move toward the poles, guided by
_________________ (microtubules lengthen). Sister chromatids remain attached at the
_________________ and move toward a pole. Homologous chromosomes (each contain sister
chromatids) move towards _________________ poles.
SPINDLE
CENTROMERE
OPPOSITE
Telophase and Cytokinesis At the start of telophase I, each half of the cell
has a complete ___________ set of chromosomes (each has 2 sister chromatids).
Cytokinesis occurs at the __________ time as telophase I and forms two haploid daughter cells.
Sometimes chromosomes _________________ and nuclear envelope and nucleoli reform.
HAPLOID
SAME
DECONDENSE
Meiosis II Prophase II
_________________ forms. During late prophase chromosomes still have
two chromatids move toward the metaphase II plate.
SPINDLE
Metaphase II Chromosomes line up on the _________________
plate. The two sister chromatids are not
_________________. Kinetochores of sister chromatids are attached
to microtubules from opposite poles.
METAPHASEIDENTICAL
Anaphase II _________________ of each chromosome separate
and chromatids come apart. Sister chromatids (of now individual
_________________) move toward opposite poles.
CENTROMERES
CHROMOSOMES
Telophase II and Cytokinesis MEIOSIS OVERVIEW 2
_________________ form, chromosomes _________________ and _________________ occurs.
Meiotic division of one parent cell produces _______ daughter cells, each with a haploid set of _________________.
Each of the four daughter cells is __________ from the other daughter cells and parent cell.
NUCLEIDECONDENSE CYTOKINESIS
FOUR
CHROMOSOMESUNIQUE
Mitosis MeiosisConserves number of chromosome sets
Reduces number of chromosome sets from two to one (diploid to haploid)
Produces daughter cells genetically identical to parent cell and each other.
Produces cells that genetically differ from parent cell and each other.Synapsis and crossing over occur.Tetrad is visible and chiasma forms (due to crossing over)Tetrads on the metaphase plane rather than individual replicated chromosomes.Separation of homologues in anaphase I of meiosis. Sister chromatids stay attached unlike in mitosis where they separate.
Genetic Variation: Three Mechanisms __________________ Assortment independent assortment
Independent assortment: the sorting of maternal and paternal _______________ into daughter cells independently of every other pair (occurs during __________________ I).
This results from the ___________ orientation of homologous chromosomes during metaphase I.
Each chromosome (paternal or maternal) may line up with its maternal or paternal homologue (______% chance for each).
Each daughter cell represents _____ outcome of all possible combinations of maternal & paternal chromosomes.
The number of possible combinations when chromosomes sort independently is ______. How many possible combinations for humans?
INDEPENDENT
HOMOLOGUES
METAPHASE
RANDOM
50
ONE
2n
2^23 ~ 8 million
Crossing over The example above suggests that each chromosome in a
gamete is __________________ paternal or maternal, but that is not accurate because of crossing over.
Crossing over produces __________________chromosomes, individual chromosomes that carry genes (DNA) from two different parents.
Beginning in prophase I, homologous chromosomes pair along the lengths.
Crossing over- one maternal and one paternal _______________ of a homologous pair are broken at the same place and rejoined to each other’s DNA. They ____________ places or cross over.
In metaphase II, chromosomes contain at least one recombinant chromatid that will go through independent assortment (no longer ______________).crossing over animation
COMPLETELY
RECOMBINANT
CHROMATID
TRADE
IDENTICAL
Random Fertilization Due to independent assortment during meiosis, a
sperm or egg represents one of 8 __________________possible chromosome combinations.
The fusion of egg and sperm produces a zygote with one of ~ 64 __________________combinations.
This does not account for crossing over… which make the combinations even greater.
MILLION
TRILLION