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Meiosis-
- type of nuclear division that reduces chromosome number from diploid to haploid
- has 2 nuclear divisions and produces 4 haploid daughter cells.
- In animals, occurs during the production of gametes.
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Homologous chromosomes-
pairs of chromosomes in diploid cell; the same kind of chromosomes carry genes for the same traits
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Tetrad-
the four chromatids of a replicated homologous pair
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Bivalent Pair-
same as tetrad
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Meiosis I-
before meiosis begins, the DNA has replicated, diploid to haploid
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Meiosis II-
exactly like mitosis, except are haploid in #
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Meiosis results in___ daughter cells that are genetically different from one another and the mother cell. They have the ______ number of chromosomes.
4. Haploid.
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Prokaryotes reproduce by____?
Binary Fission
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Single cell eukaryotes reproduce by____?
mitosis
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Multicellular eukaryotes use mitosis for____?
Growth and repair
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Meiosis occurs in multicellular eukaryotes during____?
sexual reproduction
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Chromosomal Theory of Inheritance-
the genes are on the chromosomes; therefore, the behave in a similar manner during meiosis and fertilization.
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Karyotype-
a display of chromosomes that have been paired by matching banding patterns and arranged by size from largest to smallest
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Sex chromosomes-
1 pair, 2 possible X or Y
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Autosomes-
non sex chromosomes
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Mutation-
a permanent change in the DNA, either chromosome or gene
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What are chromosome mutations due to?
- Changes in number
- changes in structure
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Monosomy-
(2N-1) a chromosome is missing, most are lethal
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Trisomy-
(2N+1) additional chromosome, many are lethal
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Spermatogenesis-
- occurs in the testes in males.
- 1 primary sperm cell-->secondary sperm cells->4 sperm
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Oogenesis-
- occurs in the ovaries.
- 1 primary egg cell->1secondary cell +1 polar body->1 egg+2nd polar body
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Importance of Meiosis-
- Keeps the chromosome number constant, generation after generation
- Helps ensure genetic variability with each generation
- 1.crossing over
- 2.independent alignment of chromosomes
- fertilization
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Mitosis-
- Somatic or body cells
- 1 nuclear division
- no pairing of chromosomes
- sister chromatids separate
- 2 daughter cells that are genetically identical to mother cell
- maintains diploid number
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Meiosis-
- sex cells only
- 2 nuclear divisions
- pairing and crossing over of chromosomes
- pairs separate, then sister chromatids separate
- 4 daughter cells that are not genetically identical to the mother cell or each other
- reduces diploid to haploid
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Autosomal Chromosome Abnormalities- Down's Syndrome-
most common autosomal abnormality, trisomy, mental retardation, women over 35 men 55
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Sex chromosome Abnormality-Turner's syndrome-
(XO)- short, broad chested, no neck, never go through puberty, only females
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Sex Chromosome Abnormality-Metafemale-
(XXX) physically normal except for menstrual abnormalities, learning disabilities
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Sex Chromosome Abnormality-Klinefelter's Syndrome-
(XXY), males with underdeveloped testes and secondary female sex charactistics, below normal intellegience
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Sex Chromosome Abnormality-Jacobs Syndrome-
(XYY) males, tall thin, severe acne, barely normal intellegiance
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Changes in structure is usually due to...?
- environmental causes-
- viruses
- chemicals
- radiation
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Inversion-
a segment of chromosome is turned around 180 degrees
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Translocation-
movement of a chromosome segment to a non-homologous
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deletion-
loss of a chromosome segment
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duplication-
presence of a chromosome segment more than once in the same chromosome
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