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The3 Sexual life cycles differ in_____
Timing in meiosis and fertilization
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Gametes _____ to form a _____ zygote that divides by _____ to develop into a muliticellular organism.
Gametes fuse to form a diploid zygote that divides by mitosis to develop into a muliticellular organism.
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Gametes are diploid or haploid?
Haploid, before fertilization.
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Sporophyte
- The multicellular diploid stage in the plant life cycle.
- Liken to zygote (diploid) in humans.
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Spores
- The haploid cells produced by sporophyte in meiosis. (Plant life cycle)
- Unlike a gamete, a spore gives rise to a multicellular individual w/o fusing with another cell.
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Explain the alternation of generations
Still not clear.
- Includes both diploid and hapoid multicellular stages.
- The multicellular diploid stage is called sporophyte. (Think human)
Meiosis in the sporophyte produces haploid cells called spores (think gametes, but not quite)
Spore are not like gametes when giving rise to a multicellular individual--they do not fuse (sperm+egg=zygote)
- The spore divides mitotically to generate a multicellular haploid stage called the gametophyte.
- (think when the haploid gamete
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Dog sperm contain 39 xs.
What are the haploid number and diploid number for dogs?
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Describe the fungi life cycle. COME BACK TO THIS
Key terms:
gametes fusing
diploid zygote
When are gametes produced?
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Gametes fuse= diploid zygote
- Meiosis= not gametes (not yet), haploid cells
- These haploid cells div/ (meiosis)
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Meiosis _____ the number of x set(s) from ____ to ____.
Meiosis reduces the number of x sets from diploid to haploid.
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Mitosis ____ the number of xs.
Mitosis conserves the number of xs.
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Three events are unique to meiosis.
1. In prophase I duplicated homologous xs line up & become physically connected along their lengths-- synapsis.
Genetic rearrangement between non sis chtds- -crossing over.
Tetrads-- four chtds of a homologous pair - Chiama
--the "x-shaped" region formed by tetrad. The physical manifestation of crossing over. - 2. Tetrads on the metaphase plate
-- at metaphase I, chromosomes line up on the metaphase plate as homologous pairs (tetrads), rather than individual replicated chromosomes, as in mitosis. - 3. Separation of homologues
-- at anaphase I of meiosis, the duplicated chromosomes of each homologous pair move toward opposite poles, but the sis chtds of each duplicated chromosome remain attached. In mitosis, sister chtds separate. -
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Meiosis I is called the ______ _______.
Reduction division. Bc it halves the number of x sets per cell.
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In meiosis, when do the sis chtds separate?
- Remember:
- In anaphase I, in meiosis I, the sis chtds do not separate. The homologous chromosomes split.
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Name the similarities and differences bwt metaphase in mitosis and metaphase in meioisis II.
- Similarities:
- Xs line up on the metaphase plate
- kinetochores of sis chtds r attached to mircrotubules extending from opposite poles
- Differences:
- Sis chtds are not genetically identical--Blame crossing over!
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Name the 3 mechanisms that contribute to the genetic variation arising from sexual reproduction.
By variation meaning the "mixed" resemblance of parents in offspring
- Independent assortment of xs
- Crossing over
- Random fertilization
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Law of independent assortment
Where one trait doesn't affect the inheritance of another. (Not all tall ppl will have blue eyes)
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When does crossing over begin
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