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what is asexual reproduction and what sort of offspring does it produce?
non sexual reproduction and results in genetically identical parent to offsprings cell
how many chromosomes are in haploid, diploid? ploidy #
- haploid is 1n
- diploid 2n
- ploidy #: number of chromosomes sets in nucleus
what is cell division and in multicellular organisms, why is it important? (5)
- cell division is precisly passed down unless mutation occurs.
- it is important because it allows
- growth and development from zygote
- replacement of damaged or dead cells
- production of reproductive cells
- cytoplasmic components are roughly divided by daughter cells
- genetic material is replicated and divided precisly by daughter cells
what are the functions of cell division? (3)
- growth and development
- tissue renewal
cell cycle order
- doubling of cytoplasm
- precise replication of DNA
what are somatic cells?
- homologus chromosome pairs have same genes produced by miosis
what is cytokinesis
division of cytoplasm
what is binary fission and in what organisms does this happen?
- the process gives two compariable cells and cell division reproduces an entire organism.
mitosis order of events
functions of mitosis?
insures that daughter cells are genetically identical to eachother and their parent cell
what does mitosis proceded by?
events of mitosis prophase (5)
- nucleoli disappear and chromatin fibers coil into chromosomes
- each chromosomes exist as two sister chromatids joined at centromere.
- spindle fiber attaches at kinetochore
- nuclear envelope disinegrates
- mitotic spindles begin to form
events of mitosis metaphase (3)
- replication of cromosomes align along the equatorial metephase plate
- in animal cells, centrosomes are positioned at opposite poles
- mitotic spindles apparatus is fully formed
events of mitosis Anaphase (2)
- sister chromatids separate, migrating towards opposite poles in a "V" shape and are considered chrmosomes
- at end of anaphase, each pole has a complete and identical set of chromosomes
events of mitosis telophase (4)
- daughter nuclei form at poles
- new nuclear envelope forms
- chromosomes unfold to form chromatin
- at end, mitosis is complete and two identical daughter nuclei are formed
functions of cytokenesis (4)
- a cell plate forms by fusion of golgi-durived vesicles
- plasma membranes arise from vesicle membranes
- a cell wall forms from vesicle content
- cleavage furrow formed by contractile microfilaments
where are the mitosis checkpoints?
- g1 Checkpoint under G1 phase
- G2 Checkpoint under G2 phase
what are the checkpoints for mitosis for?
- G1 Checkpoint insures that everything is ready for DNA replication
- G2 Checkpoint determines whether the cell can enter the M phase
in a cell cycle, what step do plants do differently after telophase?
they do not have a cleavage furrow. they only make cell wall
how many nuclear divisions are there in meiosis?
when is DNA replicated and how many times?
DNA replicates in interphase and is replicated twice
what is the difference between mitosis and meiosis
what is crossing over? what does it achieve?
- occurs between on sister chromatids during synapsis at chiasmata
what is bivalent and when does this form?
a pair of homologous chromosomes
where genetic material is exchanged
what is independent assortment? does this apply to linked or unlinked genes?
- oriantation of bivalents of metaphase I is random.
- each homologous pair aligns on metaphase I plate independently of other chromosome pairs.
- number of possible combinations is 2^n
Prophase I in miosis (3)
- 90% of miosis
- synapsis: homologous chromosomes form bivalents that are attached by a protein complex
- crossing over occurs
- nuclear envelope disintegrates
- centrosomes migrate towards opposite poles and spindle fibers begin to form.
- tetrads (bivalents) migrate towards metaphase plate.
metaphase I in miosis (3)
- tetrads align on metaphase plate
- both kinetochores of a sister chromatid pair face the same pole.
- kinetochores of homologous chromosomes face opposite poles.
anaphase I (3)
- spindle fibers guide chromosomes towards poles
- sister chromatids remain attached to the centromere
- homologous chromosomes migrate towards opposite poles
telophase I (3)
- homologous chromosome pairs reach opposite poles
- each pole contains a haploid set of chromosomes, each chromosomes still composed of two chromatids.
- cytokenesis occurs.
- in some species, chromosomes uncoil, nuclear membranes and nucleoli reappear and the cell enters a period of interkenesis
- no DNA replication occurs before Meiosis II
Prophase II (3)
- if interkenesis occurred, chromosomes condense, nuclear membranes disintegrate and nucleoli disappear
- spindle apparti (2) begin to reform
- chromosomes migrate toward metephase plate
Metephase II (3)
- chroosomes align on metephase plate
- metephase plate and spindle ases are at right angle to that of metaphase I
- kinetochores of sister chromatids point towards opposite poles.
anaphase II (2)
- centromeres of sister chromatids separate
- chromosomes migrate towards opposite poles of spindles.
Telophase II (3)
- nuclei form at opposite poles of spindles
- 4 haploid daughter cells are formed.