DNA Structure, DNA Replication and Mitosis

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DNA Structure, DNA Replication and Mitosis
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DNA, chromosomes and genestructure revision
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Structure of DNA

• DNA is made from Nucleotides that have 3 parts
• 5 carbon Sugar (deoxyribose)
• Phosphate group
• Nitrogen base (Adenine, Thymine, Guanine or
  Cytosine)

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Deoxyribonucleic acid (DNA) molecule has a double
helix (twisted ladder) structure with 2 bases of
2 nucleotides forming the rungs and the sugar and
phosphate groups forming the sides
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Anti-parallel nature of DNA

• Sugar is a 5 carbon ring (joins ladder sides to
  rungs)
• Phosphate group attaches to the 3 or the 5
  carbon (makes ladder sides)
• This gives direction to each half of the strand
  as each strand (ladder side) runs in the opposite
  direction
• Nitrogen bases join anti parallel strands as A-T
  and C-G only (make ladder rungs)

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DNA replication

• The purpose of DNA replication is to make an
  exact copy of a DNA molecule prior to cell
  division (mitosis) so each daughter cell has the
  full set of genetic material.
• Creates a chromosome with two chromatids
• Ensures each resulting cell is able to receive a
  complete set of genes from the original cell
• Three main steps
• Animations 1 2 3

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Semi-conservative nature of DNA replication

• Means less opportunity for mistakes to occur
  during replication

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DNA replication activities

• Complete cut out poster showing the semi
  conservative nature of DNA replication
• Read Biozone pages 133 134
• Do exercises 1 6 page 134
• Answer self check pg 81

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Mitosis

• The purpose of mitosis is to make exact copies of
  existing cells for growth, repair in all living
  organisms and asexual reproduction in some
• Produces 2 daughter cells genetically identical
  to parent cell
• Continuous process but has 4 main stages
• Animation 1 2

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Where mitosis occurs in plants and animals

• Plants root tips, shoot tips and inside the
  bark layer of trees. These are the active growing
  sites of plants and many larger perennial plants
  continue to grow throughout their life.
• Animals in most tissues in immature animals and
  wherever cells need replacing or repair in mature
  animals.

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Mitosis activities

• Discuss Factors affecting Mitosis handout
• Read Biozone pages 135 136
• Do Exercises 1 3 page 136

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• Your task now is to revise and study for the Cell
  End of Unit Test, by
• Read and complete Biozone pages 97 to 138
• (NB some pages not included)
• Complete Key terms Mix and Match page 138
• (NB some terms not covered)
• Review past or sample external exam papers for
  Achievement Standard 91156v1 (AS 2.4) from NZQA
  NCEA website
• Check L2 Biology Power-Points and other resources
  in MACScience blogsite
• Use other study techniques e.g. Karen Boyes, flip
  cards, mind maps
• Ask questions to clarify your understanding
  before
• Test date