Bio test 2: Mitosis, Meiosis, and sexual vs. asexual

growth, wound healing, replacement of cells, reproduction

what is cell division necessary for?

somatic cells

• diploid

• divide by mitosis

ex: body cells, skin cells

germ cells

• in reproductive organs

• divide by meiosis

mitosis 

one diploid cell divides to produce 2 genetically identical diploid cells 

• produces somatic cells

meiosis

diploid cell divides to produce 4 genetically different haploid cells

• produce gametes

interphase

what part of the cell cycle does a cell spend most of its life in?

G1, S, G2

what is part of interphase?

spindle apparatus

consists of microtubules

• moves replicated chromosomes during early mitosis

• pulls chromosomes apart during late mitosis

microtubule organizing center

any structure that organizes microtubules

• where microtubules originate from

centrosome

a structure that contains a pair of centrioles

• a MTOC in eukaryotic cells

centrioles

cylindrical structures consisting of microtubule triplets, located inside animal centrosomes

proteins

microtububles, microfilaments, and intermediate filaments are made up of ____`

microtubules

form the spindle aparatus

a-tubulin and b-tubulin

the microtubule structure is composed of ___ subunits

dimers

subunits of the microtubule structure form this

microtubule structure

• a-tubulin and b-tubulin

• made out of dimers

• dimers polymerize to form a hollow tube

• dynamic instability—helps pull chromosomes

• plus and minus end

plus end

fast growing

minus end

slow growing

actin

what is the monomer for actin filament

actin

what provides structural support and determine cell shape

actin filament

• made out of actin

• shape: double helix of 2 actin filaments

• dynamic instability

• helps form a contractile ring during cytokinesis

kinetochore

a complex protein structure that forms on each sister chromatid at the centromere region that microtubules/spindle fibers attach to

cytokinesis

• acin-myosin ring causes plasma memebrane to begin to pinch in

• two daughter cells form

• separate cytoplasm

mitosis

division of the nucleus (genetic material)

prophase, prometaphase, metaphase, anaphase, telophase

mitosis stages in order

interphase

• cytoplasmic contents/organelles increase in # and volume

• each chromosome composed of 2 sister chromatids

  • centrosomes have replicated

prophase

• chromosomes condense into chromatin

• spindle apparatus begins to form

• centrosomes start to move to opposite poles 

prometaphase

• nuclear envelope breaks down—allows the microtubules to make contact and attach to kinetochores on chromosomes

metaphase

chromosomes are lined up on the metaphase plate

• helped by spindle apparatus

metaphase plate

on an imaginary plane between the two spindle poles

anaphase

replicated chromosomes are pulled apart, creating 2 independent daughter chromosomes

• pulled to opposite sides of the cell

• kinetochores are pulled to opposite sides of the cell along with chromosomes

  • microtubules are shortening—disassemble from plus end

  • motor proteins associated with kentochores help move to minus end

telophase

• nuclear envelope reforms to create 2 independent nuclei= mitosis complete

• chromosomes decondense

• cells divide cytoplasm by cytokinesis 

vesicles

in plants a cell plate is formed by ___ with the help of microtubules to direct them in cytokinesis

clevage furrow

cytokinesis begins with the formation of the ___

actin myosin ring

attached to the inside of hte plasma membrane and will pull the membrane inwards as it tightens

binary fission

• asexual reproduction

• prokaryotes

binary fission

1. single circular chromosomes is replicated, so there are 2 copies of the genome

2. each copy becomes attached to the cell memebrane

3. the cell elongates separating the DNA attachment sites, and the chromosomes are separated from each other

asexual reproduction

2 daughter cells are produced

• may be based on mitosis

• no fusion of gametes

• identical offspring—clones

• 3 main mechanisms

sexual reproduction

offspring receive genetic material from two parents that unite in fertilization

• requires meiosis

• offspring are genetically different from parents 

• only in eukaryotic organism that can perform meiosis

ovaries, testes

in humans, meiosis happens in the ___ and ___

fertilization 

2 gametes randomly fuse together from 2 individuals

• restores the diploid chromosome #

• results in a diploid cell called a zygote

unique haploid cells (turn into gametes)

the final products of meiosis

zygote, 2n

what is formed in fertilization? what is its ploidy?

germ cell

original parent cell that gives rise to gametes

• reproductive cells

• undergo meiosis

meiosis

• reductional division 

• 2 rounds of nuclear division

• results in 4 haploid daughter cell

Half, unique

each daughter cell resulting from meiosis has ___ the number of chromosomes as each parent cell and is genetically ___

Meiosis I

• homologous chromosomes separate

• 2 haploid daughter cells result—one homology from each set

• reductional division

Prophase I

• chromosomes condense and become visible

• centrosomes migrate to the poles of the cell as the nuclear envelope breaks down

• chromosomes synapse and cross over

Synapsis

the homologous chromosomes pair up—lining up gene to corresponding gene—when the synaptonemal complex forms

crossing over

results in a random exchange of genetic info between 2 non-sister chromatids from the same homologous pair that is different every time meiosis occurs

chiasmata 

forms where the non-sister chromatids cross over

• in prometaphase 1, holds homologous pairs of chromosomes together

bivalent

a set of paired homologous chromosomes where each homologous chromosome itself consists of 2 sister chromatids

• also called a tetrad

metaphase I

• bivalents align near the midpoint of the cell—which side each is on is random

  • side by side

• homologous chromosomes are attached to spindle fibers from opposite poles

• independent assortment

independent assortment

homologous chromosomes line up randomly and are separated into different cells

anaphase I

homologous chromomes separate and begin moving toward opposite poles of the cell

telophase I

• chromosomes arrive at the pols

• cytoplasm divides to produce 2 haploid daughter cells

• each chromosome consists of 2 sister chromatids attached at the centromere

meiosis II

• equational division

• sister chromatids separate

• daughter cells are haploid

• 4 daugher cells are formed and are non-identical

Prophase II

• chromosomes condense and nuclear envelope breaks down 

• microtubules interact with chromosomes

  • chromosomes consist of two chromatids

Metaphase II

• genetic variable chromosomes line up in the middle of the cell

• spindle apparatus attaches to chromosmes at the midpoint of the cell

anaphase II

non identical chromatids of the same chromosome separate and move toward opposite poles of the cell

telophase II

• nuclear envelope reforms and cytokinesis occurs

• divides into 4 genetically different daughter cells

fused kinetochore

in prometaphase I, microtubules attached to the ___ of the sister chromatids, which homologous chromosomes are pulled to the opposite sides of the cell

individual kinetochore

in prometaphase II, microtubules attach to the ___ of the sister chromatids, and sister chromotids are pulled apart

gametes

the haploid cells produced at the end of meiosis can mature into ____

half number of chromosomes

the purpose of meiosis is to ___

Meiosis and genetic diversity

1. crossing over

2. independent assortment

3. random fertilization

mitosis and meiosis

eukaryotes can undergo ___ based on the type of cell for replication

random mutation

what is the only source of genetic variation during asexual reproduction?

4 ways of genetic variation in sexual reproduction

1. random mutations

2. meiosis 1: recombination in crossing over

3. meiosis 1: independent assortment

4. fertilization

clones

gentically identical organisms

plants

asexual reproduction is very common in __

budding

one common asexual reproduction in animals is ___

budding, fragmentation/fission, parthenogenesis 

3 mechanisms of asexual reproduction 

not the same

fragment fission and binary fission are ___

Parthenogenesis

• females produce egg cells (by meiosis, in rare cases mitosis) but fertilization does not occur

• haploid egg cells can duplicate their genome and proceed to develop into new organisms without being fertilized 

• considered asexual 

• rare—invertebrates (fisshes, lizards, birds)

budding

bump forms on organism and breaks off to grow on its own

fragmentation/fission

A form of asexual reproduction where an organism breaks into multiple fragments, and each fragment regenerates into a complete new individual.

Ex: sea stars and flatworms

gametogenesis

• the production of gametes

• occurs in gonads

testes

male gonads

ovaries

female gonads

localized

early in an animal’s development, reproductive cells/germ cells become ___ in the testes or ovaries

fertilization

the life cycle begins at ____

fertilization, mitosis, sexually produced offspring, produce gametes

life cycle of animals in order

alternation of generations

the organism passes through haploid and diploid stages that are both multicellular 

• in most plants and some fungi

sporophyte

• multicellular

• diploid

• divides by meiosis to produce haploid spores

gametophyte

• multiceullular

• haploid

• divides by mitosis to produce haploid gametes

fertilization, zygote, mitosis to sporophyte, meisois to spores, mitosis to gametophyte, mitosis to gametes

life cycle of land plants: alternation of generations

haplontic life cycle

the mature organism is haploid and the zygote is the only diploid stage.

• found in most protists, fungi, and some green algae

• fertilization, zygote, meiosis, spores, mature organism, gametes

diplontic life cycle

the organism is diploid and the gametes are the only haploid state

• found in animals, brown algae, and some fungi

• fertilization, zygote, mature organism, meiosis, gametes

daphina

freshwater crustaceans that produce only diploid, female offspring in spring and summer via parthenogeneiss

• in summer/fall: offspring can develop into males and sexual reproduction can occur 

diverse

sexaully produced offspring are genetically ___

increases

genetic diversity ____ fitness in environments with rapidly evolving parasites, deteriorating physical conditions, limited food, and rapid environmental change

requires no, rapid

asexual reproduction __ time and energy investment in mating, so it has _ population growth 

requires, slow

sexual reproduction __ time and energy investment in mating, so it has _ population growth