Chromosomes

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Chromosomes Cell Reproduction(Chapters 6 7)
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• I. Cell Division produces new cells from parent
  cells each new cell has a copy of the DNA
• A. Why do cells divide?
• 1. growth and development
• 2. repair
• 3. reproduction

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• B. Types of Cell Division
• Binary Fission occurs in prokaryotes (i.e.
  bacteria)
• a) asexual reproduction 1 parent cell
• splits into 2 identical offspring
• b) single, circular DNA

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• 2. Mitosis occurs in
• eukaryotes
• a) takes place in
• somatic cells
• (body cells
• not sperm/egg)
• b) a copy of DNA
  (chromosomes) are
• passed on to the
• newly formed cells

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• C. DNA and Chromosomes
• 1. DNA nucleic acid
• genetic information
• (the code)
• 2. gene segment of
• DNA that codes
• for a characteristic

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• 3. chromosome DNA proteins coiled into a
  single structure
• 4. chromatids two exact copies of a
  chromosome attached at the centromere
• separate during cell division

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• Each species has a unique of chromosomes
• 1. see Table 6-1 page 121
• 2. Humans 46 chromosomes

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a) 23 homologous chromosome pairs ?
homologous chromosomes - similar
size, shape, and genes in same
location ? one chromosome in each pair is
donated from each parent (23 from
mother 23 from father) ? 44
autosomes (22 autosomal pairs) and
1 pair of sex chromosomes (XX female and XY
male)
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Autosomes
Sex chromosomes
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• b) Somatic cells are diploid (2n)
• have both sets in a homologous pair
• (humans 2n 46 chromosomes)
• c) Gamete cells are haploid (n)
• have only 1 set one of the chromosomes
• from each pair (humans n 23)
• ? Gametes sperm (n 23) egg (n 23)

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• ? Zygote egg sperm join (fertilization) in
  sexual reproduction

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• 3. Karyotype photo of chromosomes in a dividing
  cell a) can reveal
• chromosomal
• disorders

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b) Types of chromosomal disorders 1)
non-disjunction too many
chromosomes (fail to separate) ex
Downs Syndrome trisomy-21
(extra 21st
chromosome)
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• 2) duplication repeat
• 3) deletion missing
• 4) inversion backwards
• 5) translocation on a different
• chromosome

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II. The CELL CYCLE
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Checkpoints
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Cancer

• Uncontrolled division of cells
• 2 types of tumors (cell masses)
• Benign
• remains at original site
• Can be removed surgically

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• Malignant
• Cells spread to other locations (metastasis)
• Treated with chemotherapy radiation
• New experimental treatments with gold
  nanoparticles

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III. Mitosis
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IV. Meiosis

• A. Forms haploid cells (gametes) for sexual
  reproduction
• B. Cuts the chromosomes in half
• 1. Haploid (n) 23 for humans
• 2. Sexual reproduction requires fertilization
• ovum (egg) sperm fuse ? diploid (2n) zygote
• 23 23
  46

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• C. Two nuclear divisions after interphase (G1, S,
  G2)
• D. Mechanisms of genetic variation
• 1. independent assortment
• 2. crossing over
• 3. random fertilization

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