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2 parents each contribute __ to an offspring.
one gamete
Gametes (and offspring) differ genetically from each other and from the parents.
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Fertilization occurs when __ fuse to form a __. The chromosome number is then __
2 haploid gametes (sperm and egg); diploid zygote; 2n
haploid = n = number of chromosomes
(Gametes contain only one set of chromosomes.)
(page 43 on slide)
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Mature organism is __ and produces gametes by__. Gametes fuse to form a __ which divides by __ to form a mature organism.
diploid; meiosis; diploid zygote; mitosis
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functions of meiosis
- reduce the chromosome number from diploid to haploid (separates homologous pairs)
- ensure that each haploid has a complete set of chromosomes
- generate diversity among the products
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During __, the homologous chromosomes pair, each consisting of __ sister chromatids. This is called __. The 4 chromatids of each homologous pair form a __
prophase I; 2; synapsis; tetrad
(page 45 on slide)
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Still in prophase I, the homologs seem to repel each other but are held together at the __ that form between the non-sister chromatids.
chiasmata
(page 45 and 48 on slide)
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Exchange of genetic material occurs at the __ called __, which results in __ & increases genetic variability of the products
- chiasmata;
- crossing over;
- recombinant chromatids
(page 45 on slide)
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During metaphase I, __ line up at the equatorial plate; homologous pairs are held together by __
homologous chromosomes; chiasmata
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During anaphase I, __ separate, resulting in __ of chromosomes, but each chromosome still consists of __ chromatids
- homologous chromosomes;
- half the diploid number (23 to each side)
- 2
(page 50 on slide)
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In telephase I, there are too many __, which need to be split in meiosis II.
chromatids (recombinant)
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In __ maternal chromosomes pair with paternal homologs during __. This doesn't occur during mitosis.
meiosis I; synapsis
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__ is one reason for genetic diversity - __ during anaphase I also allows for chance combinations.
Crossing over; independent assortment
-
differences between meiosis II and mitosis
- DNA doesn't replicate before meiosis II
- In meiosis II, the sister chromatids may not be identical because of crossing over.
- The number of chromosomes at the equatorial plate in meiosis II is half the number of those in mitosis.
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In anaphase II, __ separate & become __. After cytokinesis, the resulting products are __
- recombinant chromatids;
- daughter chromosomes;
- 4 haploid daughter cells (23 x 4)
(page 43 and 58 on slide)
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