Heredity

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Heredity
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Essential Question

• What are chromosomes and how do they cause
  mutations?

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Chromosomes

• What are they?
• Chromosomes are threadlike structures consisting
  of DNA and protein that carry genetic information.

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Chromosomes

• How many?
• Humans have 46 individual chromosomes (23 pairs)
• Types
• Chromosomes 1-22 are called autosomes.
• Chromosome pair 23 is the sex chromosomes.

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Chromosomes

• Diploid vs. Haploid
• Diploid the TOTAL number of chromosomes in an
  organism. 2n
• Haploid HALF the total number of chromosomes in
  an organism. n

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Chromosomes

• Location
• Chromosomes are located in the nucleus of a cell.
  All cells have the same set of chromosomes.
• Chromosomes are NOT visible until a cell is about
  to divide.

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Examples of chromosome numbers (diploid). Species
of chromosomes Fruit Fly 8 Rye 14 Guinea
Pig 16 Dove 16 Snail 24 Earthworm 36 Tibetan
fox 36 Cat 38 Pig 40 Mouse 40 Wheat 42 R
at 42 Rabbit 44 Syrian hamster
44 Hare 46 Human 46 Ape 48 Sheep 54 Cow
60 Horse 64 Dog 78 Chicken 78 Carp 104 B
utterflies 380 Fern 1200
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Chromosomes

• How can chromosomes cause mutations?
• Cell Cycle
• Meiosis
• Protein Synthesis

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Cell Cycle

• The period between the birth and the death of
  a cell

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Cell Cycle

• Phases
• Interphase
• M Phase
• Cytokinesis

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Cell Cycle

• Interphase
• Phases
• G1
• S
• G2

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Graphic Organizer
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G1 phase

• The normal period for a cell.
• Cell is growing and carrying on the normal
  functions for the cell.
• Cell grows to a point and problems will arise
• DNA will overload if a cell gets to large, extra
  stress is put on the DNA in the cell.
• Surface area cannot accommodate the volume of the
  cell
• Cell will have to divide.

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Why do cells divide?

• Heal wounds
• Grow new body parts
• Replace dying cells
• Produce eggs and sperm

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S phase

• In preparation of cell division, the DNA will
  make copies of itself.

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What is DNA? Where is DNA located?

• DNA stands for deoxyribonucleic acid. It is our
  genetic code.
• In prokaryotic cells in cytoplasm
• In eukaryotic cells in the nucleus. It makes up
  chromosomes.

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Who discovered DNA?

• James Watson and Francis Crick proposed a model
  in 1953. It is a very large molecule, but is
  made of only a few chemicals.

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What does DNA look like?

• Words
• Each nucleotide is made of a sugar (deoxyribose),
  a phosphate group and a nitrogen base.
• DNA is called a double helix. It looks similar
  to a twisted rope ladder.

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What does DNA look like?

• What are the 4 nitrogen bases?
• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Thymine (T)

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What does DNA look like?

• Chargaffs Rule
• Adenine pairs with Thymine.
• Guanine pairs with Cytosine

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What does DNA look like?
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What does DNA look like?

• Practice Problem
• Find the complementary strand for the following
  DNA sequence
• ATTGCTCCGTTA

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DNA Replication

• Enzymes unzip a molecule of DNA. Hydrogen bonds
  are broken.
• Each individual strand serves as a template to
  make a new strand.
• Enzyme called DNA Polymerase allows individual
  nucleotides to produce DNA that is complementary
  to the original DNA. This enzyme also
  proofreads.
• DNA replication occurs in 2 directions.

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G2

• During this phase, the cell continues to grow.
  This phase is very similar to G1, but G2 helps
  make sure that the cell is ready to proceed to
  mitosis.