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L10: Mitosis & Meiosis

BIOL 153/LBlack Hills State Univ.Ramseys

I. Eukaryotic chromosomesA. Structural components

1. Chromatin

DNA and associated proteins

2. Nucleosomes

chromotin packing unit ('beads on a string')

3. Fibers, looped domains, condensed coils

higher order organization of chromatin

Fig. 8-4Raven p. 154

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I. Eukaryotic chromosomesB. Location

1. In nucleus

1. In nucleus

interphase and early prophase

1. In nucleus

interphase and early prophase

2. Across cell

1. In nucleus

interphase and early prophase

2. Across cell

late prophase, metaphase, anaphase

1. In nucleus

interphase and early prophase

2. Across cell

late prophase, metaphase, anaphase

chromosomes spend most time in nucleus (interphase)

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nuclear envelope degrades during prophase

nuclear envelope reforms during telophase

I. Eukaryotic chromosomesC. Size and content

1. Nucleotides: huge variation in base pairs

• flowering plants: very high• mammals: kinda high• birds: low

1. Nucleotides: huge variation in base pairs

• flowering plants: very high• mammals: kinda high• birds: low

2. Length:0.5 g DNA stretches earth to sun!

Wake-robin Trillium

~68 m of DNA

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Homo sapiens

~2 m of DNA

I. Eukaryotic chromosomesD. Genes

1. A gene specifies amino acid order in a protein

2. Allele = alternate version of gene

3. Locus = specific gene location on chromosome

I. Eukaryotic chromosomeE. Ploidy

1. Haploid: 1 set of chromosomes

2. Diploid : 2 sets of chromosomes

3. Polyploid: >2 sets of chromosomes

4. Homologous chromosomes

chromosomes with same genes, in same order (may have different alleles)

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hypothetical organism with only three chromosomes:

Haploid Diploid

Haploid Diploid Triploid Tetraploid Haploid Diploid Triploid TetraploidPolyploid

Haploid Diploid Triploid TetraploidPolyploid

homologous

Haploid Diploid Triploid TetraploidPolyploid

homologous homologous homologous

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one particular chromosome in hypothetical diploid organism:

homologous chromosomes

2 different alleles

2 different alleles

1 allele (only)

2 different alleles

homologous chromosomes

II. Mitosis overview A. Location

somatic (body) cells

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B. Goal

make exact chromosome replicates(occurs with cell division)

C. Examples

C. Examples

animal developmentchicken egg

plant growthash seedling

if mitosis makes exact copies...

how do bloody blobs become chicks?how do seeds become trees?

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III. Meiosis overview A. Location

gametic (reproductive) cells

B. Goal

reduce (half) chromosome number(occurs with cell division)

C. Examples

testes à sperm

ovary à egg

anther à pollen

IV. Shared features of mitosis & meiosis A. Naming of stages

[I]P-MAT

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A. Naming of stages

[Interphase]ProphaseMetaphaseAnaphaseTelophase

[I]P-MAT

B. DNA replication

Interphase

C. DNA condensing

Prophase

D. Lining up of chromosomes

Metaphase

E. Separation (chromatids/chromosomes)

Anaphase

V. Particular features of meiosis

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A. Two rounds of division

P-MAT I P-MAT II"Reductional Division" "Equational Division"

A. Two rounds of division

P-MAT I P-MAT II"Reductional Division" "Equational Division"

reduces chromosome # in half divides chromatids

Meiosis I"Reductional Division"

Meiosis II"Equational Division"

B. Crossing over of homologous chromosomes (recombination)

Prophase I

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C. Separation of homologous chromosomes(reduction)

Anaphase I & Telophase I