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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
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how many chromosomes are in haploid, diploid? ploidy #
- haploid is 1n
- diploid 2n
- ploidy #: number of chromosomes sets in nucleus
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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
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what are the functions of cell division? (3)
- reproduction
- growth and development
- tissue renewal
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cell cycle order
- doubling of cytoplasm
- precise replication of DNA
- mitosis
- cytokinesis
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what are somatic cells?
- diploid
- homologus chromosome pairs have same genes produced by miosis
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what is cytokinesis
division of cytoplasm
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what is binary fission and in what organisms does this happen?
- prokaryotes
- the process gives two compariable cells and cell division reproduces an entire organism.
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mitosis order of events
- prophase
- metaphase
- anaphase
- telophase
- cytokensis
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functions of mitosis?
insures that daughter cells are genetically identical to eachother and their parent cell
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what does mitosis proceded by?
DNA replication
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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
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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
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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
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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
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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
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where are the mitosis checkpoints?
- Interphase:
- g1 Checkpoint under G1 phase
- G2 Checkpoint under G2 phase
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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
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in a cell cycle, what step do plants do differently after telophase?
they do not have a cleavage furrow. they only make cell wall
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how many nuclear divisions are there in meiosis?
4
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when is DNA replicated and how many times?
DNA replicates in interphase and is replicated twice
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what is the difference between mitosis and meiosis
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what is crossing over? what does it achieve?
- occurs between on sister chromatids during synapsis at chiasmata
- recombination
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what is bivalent and when does this form?
a pair of homologous chromosomes
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where genetic material is exchanged
the chiasmata
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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
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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.
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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.
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anaphase I (3)
- spindle fibers guide chromosomes towards poles
- sister chromatids remain attached to the centromere
- homologous chromosomes migrate towards opposite poles
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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.
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Interkinesis (2)
- 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
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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
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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.
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anaphase II (2)
- centromeres of sister chromatids separate
- chromosomes migrate towards opposite poles of spindles.
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Telophase II (3)
- nuclei form at opposite poles of spindles
- cytokenesis
- 4 haploid daughter cells are formed.
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