Spontaneous Generation of Life

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Spontaneous Generation of Life?
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Animalcules- tiny people in sperm?
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Blending of Parents traits
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So What REALLY Happens?

• The number of chromosomes divide to make gamete
  cells.
  
• When does this occur?
• Before sexual reproduction

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Law of Segregation

• Two members of a gene pair segregate (separate)
  from each other during the formation of gametes.
  
• What is a gene pair?
• When, in meiosis does segregation occur?
• Anaphase I

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Test Crosses

• SS x SS - true breeding (100 homozygous
  dominant.)
  
• ss x ss - true breeding (100 homozygous
  recessive.)
  
• How do you determine whether an individual with
  the dominant phenotype is homozygous or
  heterozygous?
  

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Test Cross

• Used to detect heterozygous condition.
• In peas, the allele for tall plant height (T) is
  dominant over the allele for short plant height
  (t)
  
• What cross would you do to determine the
  genotype of a tall pea plant?
  
• What results would you expect if the tall plant
  is TT?
  
• What results would you expect if the tall plant
  is Tt?

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Law of Independent Assortment

• Alleles for different traits assort (segregate)
  independently of one another.
  
• Genes on different chromosomes behave
  independently in gamete production.
  
• Why does this law not apply to a one trait
  cross?
  
• When, in meiosis does this occur?

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Probability

• Probability the of times an event is expected
  to happen / the of opportunities for an event
  to happen.
  
• For example, The probability of rolling a 2 on a
  dice in one trial is
  
• 1/6
• The rule of multiplication states that the
  probability of two or more events happening at
  the same time is the product of the independent
  events.
• What is the probability of rolling two 2s?
• (1/6) x (1/6) 1/36
• How can the principles of probability be used to
  predict the outcomes of genetic crosses?
  

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• Ie. RrYy x RrYy
• What is the probability of obtaining an
  offspring with the genotype rrYY?
  

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• What would the gametes of a plant of genotype
  SsYy have?
  
• SY, Sy, sY, and sy
• Each gamete will receive either an S or
• s allele, and either a Y or y allele.
• Following a SsYy x SsYy cross, what fraction of
  the offspring are predicted to have a genotype
  that is heterozygous for both characteristics?

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• When lots of genes are considered, you must use
  probabilities to answer questions.
  
• AaBbCcDdEeFf x AaBbCcDdEeFf
• What proportion of progeny will be AAbbCcDDeeFf?

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• In the cross AaBbCcDdEeFf x AaBbCcDdEeFf
• What proportion of the progeny will be
  AaBBccddEEff?

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Ratio9331
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• Deep down in the Pacific Ocean in the city of
  Bikini Bottom, square pants (S) are dominant to
  round pants (s), and yellow skin (Y) is dominant
  to green skin (y). Sponge bob is a Yellow
  skinned, square pants sponge, whose mother had
  green skin and round pants.
• A. What is Sponge Bobs genotype?
• B. Sponge Bob wants children and he mates with a
  spongey woman with square pants and green skin.
  Her father had curved ears. What is her
  genotype?
• C. What is the phenotypic ratio of the children
  that are expected as a result of this mating?
  
• D. How many of their children will have the
  following genotype?
  
• PPYy? Ppyy?

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• A man with brown eyes marries a woman with blue
  eyes. The mans mother had blue eyes. What is
  the probability that they will have a blue-eyed
  child? 
• B brown     b blue
• You do not immediately know the genotype of the
  brown-eyed man because he could be either Bb or
  BB.  Begin to state the cross by using a blank
  for the unknown gene.  One of the genes of the
  brown-eyed man must be B or he would have blue
  eyes.  His genotype is B_ and the cross is B_ x
  bb -- .  Fill in any blanks in a problem by
  using other information in the problem.  The
  brown-eyed man had a blue-eyed mother.  Her
  genotype must be bb (If she had even one B gene
  she would have brown eyes).  The man's mother
  could give him only a b gene so his genotype must
  be Bb.  The cross now is Bb x bb --.  Do the
  cross. 

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