Characteristic

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Characteristic 4

• All living things reproduce using the same
  genetic mechanism (code)

• Each organism reproduces its own species
• Offspring inherit genetic instructions from their
  parents through a molecule called DNA
• Offspring can differ from their parents (genetic
  variation)

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Mitosis Meiosis

• Making New Cells from Old Cells

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Passing on Information

• Genetics is the study of the transfer of
  information at the level of the cell.
• Genetic information is found on DNA molecules
  within each cell nucleus
• DNA is divided into chromosomes
• Chromosomes come in homologous pairs
• Chromosomes are divided into genes
• Genes control traits

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Chromosomes

• Chromosomes are found in the nucleus of the cell
• Each organism has a different number of
  chromosome pairs (from one pair to hundreds of
  pairs)
• Humans have 23 pairs of chromosomes

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New Terminology

• Diploid a body cell that has homologous pairs of
  chromosomes. Human diploid cells have 23
  chromosome pairs (46 chromosomes).
• Autosome body cells (everything except for sex
  cells) that are diploid

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New Terminology

• Haploid a sex cell that has only one set of
  chromosomes (one from each pair). Human haploid
  cells have 23 chromosomes.
• Gamete sex cell (sperm, egg) that are haploid

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Mitosis the Cell Cycle

• Mitosis is required
• for growth, repair, and
• replacement of cells.
• DNA passes from old
• to new cells during the cell cycle
• A diploid parent cell duplicates its DNA, then
  splits in half, with one copy of DNA in the two
  new diploid daughter cells
• Mitosis creates autosomes

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How Does the Cell Cycle Work?

• Prior to division, the DNA relaxes in the
  nucleus. This is the Interphase stage

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Replication of DNA

• Before dividing, each chromosome creates a copy
  of itself
• The copies thicken to form in an X shape

Before Replication After Replication
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Mitosis

• After DNA replication, the nucleus of the cell
  divides in a series of four steps called mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase

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• Jigsaw

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Prophase

• Nucleus dissolves, and fibers attached to
  centrioles stretch across the cell

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Metaphase

• The chromosomes line up on the cell equator,
  and the fibers attach to them from both sides

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Anaphase

• The fibers shorten, splitting the chromosomes
  in half and pulling one half to each pole

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Telophase

• A new nucleus begins to form around each set of
  chromosomes, and the cell starts to split in half

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Cytokinesis

• After mitosis, the cell splits into two
  daughter cells in a step called Cytokinesis
• In animal cells, a cleavage furrow develops and
  the cell simply splits in two
• In plants, a cell plate grows across the center
  of the cell, dividing it in half

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Cell Cycle MitosisSummary

• Mitosis is a way for cells to pass information to
  new autosomal cells within the same organism
• The cell cycle mitosis result in two diploid
  daughter cells that are identical to the original
  diploid parent cell
• Cell cycle and Mitosis are important in growth,
  replacement, and repair of all body cells

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Meiosis
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Sexual Reproduction

• When the sperm fertilizes the egg, moms dads
  DNA is combined together
• To produce a baby with a normal of chromosomes,
  each sperm and egg must have half the number of
  chromosomes

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Gametes Sex Cells Sperm and Eggs

• Found only in the testicles ovaries
• Gametes are

• haploid they have 23 chromosomes (no pairs)
• Formed through meiosis

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Gametes Differences between gametes and
autosomes

• Gametes are sex cells
• Gametes are only in the testicles and ovaries
• Gametes are haploid
• Gametes are made from meiosis
• Meiosis produces 4 different haploid gametes

• Autosomes are body cells
• Autosomes are found everywhere else in the body
• Autosomes are diploid
• Autosomes are made from mitosis
• Mitosis produces 2 identical diploid body cells

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Meiosis produces four different haploid daughter
cells from one diploid parent cell

• Original diploid 4 haploid
• parent cell daughter
  cells

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How does Meiosis Work?

• The cell makes an extra copy of DNA
• Chromosomes cross over to exchange information
  before the first division
• The cell divides two times
• At the end of meiosis, there are 4 haploid
  daughter cells
• The two chromosomes from each pair will end up in
  different daughter cells

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A look at Meiosis
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Diploid to Haploid Diploid to Diploid

• After meiosis, each daughter cell will have half
  as many chromosomes as the parent.

• After mitosis, the daughter cell will have the
  same number of chromosomes as the parent.

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Meiosis vs. Mitosis

• If the parent cell has 60 chromosomes, how many
  will the daughter have after meiosis?
• Daughter cells produced by mitosis have 16
  chromosomes. How many did the parent cell have?
• A sperm has 15 chromosomes. How many chromosomes
  did the parent cell have?
• If a daughter cell has 10 chromosomes and the
  parent had 20, was the daughter cell made through
  meiosis or mitosis?

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Crossing Over

• Homologous chromosomes move very close together
  so close that they sometimes they swap pieces.
• This creates brand new combinations of genes on
  each chromosome
• Crossing over leads to genetic variation the
  offspring will have different traits than either
  of their parents

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Other Reproductive IssuesGrab Bag of Knowledge

• Selective Breeding
• Asexual reproduction
• Alternation of generations
• Incomplete metamorphosis
• Complete metamorphosis

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Selective Breeding
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Dairy cows have been modified through selective
breeding for large udders and high milk
production. As a result, many cows have udders so
large that they cannot walk without swinging
their legs out to the side.
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Asexual Reproduction

• Asexual reproduction is when one parent
  produces one or more identical offspring

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Examples of Asexual Reproduction

• A branch of a tree grows into a new tree when
  planted

• Hydra create offspring that grow from their body
  and then pinch off

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Sexual Reproduction

• Sexual reproduction involves the fertilization
  of an egg by a sperm (two parents). Offspring are
  different from the parents.

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Animal Life CyclesMetamorphosis

• Some organisms go through changes in form as they
  grow
• Insects undergo metamorphosis
• Incomplete metamorphosis has 3 stages egg,
  nymph, adult
• Complete metamorphosis has 4 stages egg, larvae,
  pupae, adult

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Incomplete Metamorphosis Three stages

• Egg
• Nymph similar to adult but cant reproduce
• Adult

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Incomplete Metamorphosis in Grasshoppers

• Eggs

• Nymph
  Adult

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Complete MetamorphosisFour stages

• Egg
• Larvae (caterpillar)
• Pupae (cocoon)
• Adult

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Butterfly Development

• Development of the crow butterfly (Above left)
  egg (Left) larvae Above pupae and cocoon next
  slide adult

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Plant Life CyclesAlternation of Generations

• Plants alternate between a diploid and haploid
  phase. This is the alternation of generations.

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What kind of reproduction is shown here?
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What kind of reproduction is shown here?
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What kind of reproduction is shown here?
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What kind of reproduction is shown here?
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What kind of reproduction is shown here?
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What kind of reproduction is shown here?
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What kind of reproduction is shown here?
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