Diploid vs. haploid

1
Diploid vs. haploid

• chromosomes
• one copy of each one set
• N 2N
• N varies greatly from species to species
• N constant w/in species
• Humans 2N 46
• Hermit crab 2N 256
• Ascaris 2N 2
• Ophioglossum reticulatum 2N 1,260 (actually, N
  15 84N)

2
Diploidy vs. haploidy

• Chromosomes
• Homologues
• Maternal and paternal
• genes, alleles, loci
• genotype vs. phenotype
• homozygote vs. heterozygote

3
Homologues
4
Genotype AA Bb cc Phenotype ABc
5
Diploidy vs. haploidy ...

• Chromosomes
• morphology
• karyotypes
• prior to cell division
• duplicated chromosomes - chromatids
• centromere placement
• metacentric, acrocentric, telocentric
• telomeres
• banding patterns

6
Mitosis vs. Meiosis

• Mitosis leads to growth, somatic cells (usually)
• one cell forms two cells
• 2N ? 2N (1N ? 1N)
• daughter cells are identical
• Meiosis leads to gametes (usually)
• one cell forms four cells
• 2N ? N
• two divisions
• daughter cells are not identical

7
Cell Cycle

• G1
• growth, cell performing its function
• S
• synthesis of DNA
• G2
• continued growth, cell metabolizing
• Division (mitosis or meiosis)

8
Mitosis

• 5 Stages
• Interphase (G1-S-G2)
• Prophase
• condensation of chromosomes
• breakdown of nuclear membrane
• centrosome duplicates, move to opposite poles
• spindle fibers begin to form

9
Interphase --gt Prophase
Single chromosomes Duplicated chromosomes
(not visible) (chromatids) (visible)
10
Mitosis ...

• Metaphase
• nuclear membrane gone
• centrioles at opposite poles
• spindle fibers attached to centromeres and
  centrosomes
• chromosomes move to cell equator - metaphase
  plate

11
Metaphase
centrisome
metaphase plate
12
Mitosis ...

• Anaphase
• spindle fibers shorten, pulling chromatids apart
  - disjunction
• chromatids separate, move to opposite poles

13
Anaphase
14
Mitosis

• Telophase
• chromosomes relax
• nuclear membrane reforms
• plants cell wall animals cell furrow
• cytokinesis complete

15
Telophase
16
Mitosis in a diploid cell
17
Mitosis in a haploid cell