Meiosis
E.Q.: What is the purpose of Meiosis? What are the
sources of variation in a population?
 Definition: A type of cell division that only certain cells
in the gonads of multicellular organism undergo to
produce gametes (sex cells)
 In the process of Meiosis, PMAT happens twice
- 1st = reduce the amount of chromosomes (cut in half)
- 2nd = divide into gametes
 MEIOSIS IS THE FIRST STEP OF SEXUAL REPRODUCTION!!!
 Fertilization is the event when the sperm meets the egg.
- Creates a single cell called a zygote.
 Purpose of Meiosis:
1. To create gametes that have ½ the genetic
information as the parent.
2. In INCREASE VARIATION in a population.
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 Why is variation necessary?
1. To increase the chance of an individual’s survival and,
therefore, whole populations of that species.
2. Create challenges for natural predators of that
species.
 Sources of Variation:
1. Recombinant DNA = DNA in sperm + DNA in egg =
new combination of DNA in zygote
2.
Crossing over = an event that take place in meiosis
during Prophase I where homologous chromosome
“gene swap.”
- Homologous chromosomes (homologues) = A pair
of chromosomes that contain the same genetic
information.
o One from mom; one from dad = homologous
pair.
3. Mutation = Changes in nucleotide (base) sequence.
- Can affect one gene; therefore, the production of
one protein.
- Can affect a whole chromosome (many genes);
therefore, the development of an organism.
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