Today

1
Todays Agenda

• Bellringer What does it mean to be homozygous
  for a trait? What about heterozygous?
• Turn in writing from yesterday
• Genetics Part 2

2
Genetics Part 2
3
Todays Goals

• I can identify Mendels role in genetics
• I can use Punnett squares to predict the results
  of crosses
• I can compare and contrast an individuals
  phenotype and genotype

4
Punnett Squares

• A punnett square is a chart that shows all the
  possible combinations of alleles that can result
  from a genetic cross
• Helps determine the probability of a particular
  outcome

5
Punnett Squares

• Page 311
• The possible alleles that the parents can pass on
  are written across the top and left side
• The boxes represent possible combinations of
  alleles that offspring can inherit
• Each box has an one allele from each parent, for
  a total of 2

6
Punnett Square

• The allele that each parent will pass on is based
  on a chance
• You can also use a Punnett square to predict
  probabilities!
• Look at Applying Math on page 311

7
Phenotypes and Genotypes

• Phenotype an organisms physical appearance
• Ex. Tall or short
• Genotype an organisms allele combination
• Ex. TT, tt, Tt

8
Phenotypes and Genotypes

• If you were to look at tall plants you would not
  be able to see the difference because they have
  the same phenotype, but they have two different
  genotypes
• Short pea plants would all have the same
  phenotype and genotype

9
Mendel and the Pea Plants

• Mendels experiments with pea plants lead to
  modern genetics
• He crossed two homozygous (purebred) pea plants
  (one tall/one short)
• He created heterozygous (hybrid) plants that were
  a combination of their parents (all tall)

10
Mendel and Probability

• When Mendel crossed two hybrid pea plants, ¾ of
  the offspring were tall and ¼ was short
• The probability of producing a short pea plant
  was 1 in 4 or 25
• Mendel was the first scientist to recognize that
  probability can be used to predict the results of
  genetic crosses

11
Revisiting Todays Goals

• I can identify Mendels role in genetics
• I can use Punnett squares to predict the results
  of crosses
• I can compare and contrast an individuals
  phenotype and genotype