If you flip a coin what are the chances it will land on heads? Tails? Suppose that you flipped the coin and got heads. What are the chances that you will get heads again?

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DO NOW
4/25
If you flip a coin what are the chances it will
land on heads? Tails? Suppose that you flipped
the coin and got heads. What are the chances that
you will get heads again?

• Objectives
• Explain how genes and alleles are related to
  genotype and phenotype.
• Use the information in a Punnett square.

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A Great Idea

• Mendel knew that there must be two sets of
  instructions for each characteristic.
• The instructions for an inherited trait are
  called genes.
• The different forms (often dominant and
  recessive) of a gene are alleles.

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A Great Idea, Continued

• Phenotype An organisms appearance.
• Genes affect the phenotype.
• Genotype The combination of inherited alleles
  together.
• A genotype that has 2 dominant OR recessive
  alleles is homozygous or true breeding (PP or
  pp).
• A genotype that has one recessive and one
  dominant is heterozygous (Pp).

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A Great Idea, Continued

• Genotype vs. Phenotype
• An example of a genotype that a butterfly can
  inherit is AA.
• The phenotype this offspring will have is dark
  wings.

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• Punnett Squares are used to organize all the
  possible genotype combinations of offspring from
  particular parents. What are the genotypes?
  Phenotypes?

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What are the Chances?

• A gene is made up of 2 alleles.
• Probability is the mathematical chance that
  something will happen and is often written as a
  fraction or percentage.
• Probability is used in genetics to figure out the
  percentage of offspring that will have a
  particular phenotype.

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DO NOW
4/26
In pea plants, the genes for tall plants (T) are
dominant over the genes for short plants
(t). Cross a homozygous dominant tall pea plant
(TT) with a short (homozygous recessive) pea
plant (tt). What percentage of short pea plants
will appear in the offspring of this cross?

• Objectives (Do Not Have to Re Copy)
• Explain how probability can be used to predict
  possible genotypes in offspring.
• Describe 3 exceptions to Mendels observations.

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Calculating Probability
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What are the Chances? Continued

• Genotype Probability
• To have white flowers, a pea plant must receive a
  lower case p allele from each parent.
• Each offspring of a Pp X Pp cross has a 50
  chance of receiving either a P allele or p
  allelle from the parent.
• So, the probability of inheriting two p alleles
  is 1/2 X 1/2, which equals 1/4, or 25.

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Mendels Principles

• Mendel came to 3 important conclusions from his
  experimental results
• The inheritance of each trait is determined by
  units or factors that are passed on to
  descendants (these units were later called genes)
• An individual inherits one such gene from each
  parent for each trait.
• A trait may not show up in an individual but can
  still be passed on to the next generation.

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More About Traits (Exceptions to Mendels
principles)

• Incomplete Dominance
• Researchers have found that sometimes one trait
  is not completely dominant over another.
• When a red and white snapdragon flower breed it
  makes offspring that are all pink.
• Example in humans Wavy hair

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More About Traits (Exceptions to Mendels
principles)

• One Gene, Many Traits
• Sometimes one gene influences multiple traits.
• Example A gene for fur on a tiger to be white
  may also code for the tigers eyes to be blue.
• Many Genes, One Trait
• Some traits, such as the color of your skin,
  hair, and eyes, are the result of several genes
  acting together. This is called multiple alleles.
  
• Examples Eye color

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More About Traits, Continued

• The Importance of Environment
• Genes arent the only influences on traits.
• A combination of things determine an individuals
  characteristics.
• Example Diet affects growth and sun affects skin
  tone
• Lifestyle choices can also affect a persons
  traits.

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• What is the genotype of the offspring represented
  in the upper left-hand box of the Punnett square?
• A RR
• B Rr
• C rr
• D rrr

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2. What is the genotype of the offspring
represented in the lower right-hand box of the
Punnett square? A RR B Rr C rr D rrr
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3. What is the ratio of Rr (purple-flowered
plants) to rr (white-flowered plants) in the
offspring? A 13 B 22 C 31 D 40