Genetics

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Genetics

• A Monk and his Methods

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Gregor Mendel

• In 1865 he published his observations of pea
  plants.
• His work went unnoticed for several decades,
  before the realization of his genius set in.

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What did he do?

• He worked with Pea plants.
• He noted several variations in the
  characteristics of his plants
• Variations such as
• Flower color (Purple or White)
• Seed Texture (Round or Wrinkled)

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Careful Observations

• Mendel did several experiments where he
  cross-bred (mated) plants of various
  characteristics.
• He took careful notes and recorded all of his
  observations
• Mendel made some astounding conclusions

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The Conclusions

• Mendel noted that some traits seemed to prevail
  over others..
• An example
• Mendel cross bred a pea plant with white flowers
  and a pea plant with purple flowers. The
  majority of plants produced had purple flowers,
  few had white flowers.

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Why is this important?

• These observations lead to the conclusion that
  certain traits are DOMINANT over other traits.
• The traits that are not DOMINANT are called
  RECESSIVE.

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Patterns of Inheritance

• Mendel noted these patterns of inheritance among
  pea plants.
• Today we can apply these ideas to human
  inheritance.

This family inherited the Cat-face gene.
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Lets Take a Closer Look

• What is actually happening when traits are
  inherited????
• Remember traits (genes) are carried on
  CHROMOSOMES.
• You have TWO copies of EACH chromosome.
• This means you have TWO copies of EACH gene.

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Your Genes

• You received one half of your genes from your
  mother and the other half from your father.
• These genes complement each other and express
  themselves as a PHENOTYPE.
• PHENOTYPE- physical characteristic of an organism
  (What you see)

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Phenotype Vs. Genotype

• Your phenotype (what you see) may be different
  than your GENOTYPE
• GENOTYPE- the combination of ALLELEs that an
  organism has for a trait
• ALLELE- a variation of a trait

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Lets Check it Out
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Dominant Vs Recessive

• Some alleles are Dominant and some are Recessive

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Homozygous and Heterozygous

• Genotypes can be Heterozygous or Homozygous.
• A Heterozygous genotype has one of each allele.
  (Aa)
• A Homozygous genotype only has one type of allele
  (aa or AA)

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Recessive

• Only those individuals who have the homozygous
  recessive genotype will have the recessive
  phenotype.

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References

• http//www.jic.bbsrc.ac.uk/germplas/pisum/zgs4f1.g
  if
• http//www.laskerfoundation.org/rprimers/gnn/timel
  ine/images/first_second_generation.gif
• http//www3.sympatico.ca/the_adams_family/cat-fami
  ly.png
• http//www.awa.com/norton/figures/fig1307.gif
• http//library.thinkquest.org/C0118084/Gene/Geneti
  c_variation/dominant_recessive_files/homologous_ch
  romosomes.gif
• http//site.voila.fr/bioafb/loismend/genelapi.GIF
• http//www.glasgowzoo.co.uk/images/warmblooded/wal
  2.jpg