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

http://royaleb.files.wordpress.com/2009/04/mitosis_phases1.jpg

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

Evolutionary Significance?Natural selection