I. Eukaryotic chromosomes A. Structural components L10: Mitosis - - PDF document

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L10: Mitosis & Meiosis

BIOL 153/L Black Hills State Univ. Ramseys

• I. Eukaryotic chromosomes
• A. 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. 8-4

Raven p. 154

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• I. Eukaryotic chromosomes
• B. 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 chromosomes
• C. 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 chromosomes
• D. 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 chromosome
• E. 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 Tetraploid Polyploid Haploid Diploid Triploid Tetraploid Polyploid homologous Haploid Diploid Triploid Tetraploid Polyploid homologous homologous homologous

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• ne 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 development chicken egg plant growth ash 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

• vary 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] Prophase Metaphase Anaphase Telophase [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