Mendel and His Peas

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Mendel and His Peas
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• What is genetics?
• Genetics is the study of heredity, the process
  in which a parent passes certain genes onto their
  children. (http//www.nlm.nih.gov/medlineplus/enc
  y/article/002048.htm)
• What does that mean?
• Children inherit their biological parents genes
  that express specific traits, such as some
  physical characteristics, natural talents, and
  genetic disorders.

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Mendelian Inheritance

• The inherited traits are determined by genes that
  are passed from parents to children.
• A child inherits two sets of genesone from each
  parent.
• A trait may not be observable, but its gene can
  be passed to the next generation.

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Mendelian Inheritance

• Each person has 2 copies of every geneone copy
  from mom and a second copy from dad. These
  copies may come in different variations, known as
  alleles, that express different traits.
• For example, 2 alleles in the gene for freckles
  are inherited from mom and dad
• allele from mom has freckles (F)
• allele from dad no freckles (f)
• child has the inherited gene pair of alleles, Ff
  (F allele from mom and f allele from dad).

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• Genetics
• Gene segment of DNA that codes for a specific
  trait
• Allele alternative forms of a gene. An
  individual inherits two alleles for each gene,
  one from each parent. If the two alleles are the
  same, the individual is homozygous for that gene.
  If the alleles are different, the individual is
  heterozygous.
• Dominant allele that masks other from being
  expressed (will show if present)
• Recessive allele that is masked when dominant
  is present (show only if other is not present)

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• Genotype the alleles an organism possesses
• Phenotype an organisms physical appearance
• Homozygous both alleles are the same
• Ex. YY or GG
• Heterozygous alleles are different
• Ex. Yy or Gg

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• Principle of Segregation genes separate during
  meiosis
• What phase of meiosis would this occur?
• Anaphase II

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• Principle of Segregation genes separate during
  meiosis
• Independent Assortment genes for different
  characteristics are distributed to gametes
  independently

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Punnett Square

• Test Cross A test cross is a way to explore the
  genotype of an organism. Early use of the test
  cross was as an experimental mating test used to
  determine what alleles are present in the
  genotype

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Incomplete Dominance

• With incomplete dominance, a cross between
  organisms with two different phenotypes produces
  offspring with a third phenotype that is a
  blending of the parental traits.
• Ex.

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Codominance

• With codominance, a cross between organisms with
  two different phenotypes produces offspring with
  a third phenotype in which both of the parental
  traits appear together.
• Ex.

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• STOP POINT - GENETICS INTRO.

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• Sex Linkage trait determined by alleles on the
  sex chromosomes
• Incomplete Dominance - two or more alleles
  influence phenotype
• Co-Dominance Both alleles are expressed equally
• Multiple Alleles traits that have multiple
  alleles
• Ex. Blood type IA, IB, i
• Polygenic traits two or more genes for one
  trait.

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