Genetics and Heredity

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Genetics and Heredity

• Chapter 8

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Mendel Studied 7 Characters in the Garden Pea
(Pisum sativum)

• Flower color.
• Flower position.
• Seed color.
• Seed shape.
• Pod color.
• Pod shape.
• Stem length.

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Mendels Methods

• Cross-pollination- the transfer of pollen from
  one plant to the stigma of another.
• Self-pollination
• Artificial cross-pollination
• Monohybrid crosses- an experimental cross between
  individuals that differ by a single trait.
• First (F1) and second (F2) generations.

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Mendels F1 Observations

• One of the traits could be seen in the F1
  generation Dominant
• One of the traits could not be seen in the F1
  generation Recessive

100 Purple
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Genetic Terminology

• Phenotype- an organisms traits.
• Genotype- an organisms genetic makeup.
• Homozygous- identical alleles for a gene.
• Heterozygous- two different alleles for a gene.

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Genetic Terminology 2

• Allele- one of 2 or more alternative forms of the
  same gene.
• Gene- a sequence of DNA that codes for a protein.
• Locus- the position on a chromosome occupied by a
  gene.

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Mendels F2 Observations

• Flower color
• Purplewhite
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Mendels Dihybrid Cross

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Mendels Work Yielded These Genetic Rules

• Alternative versions of genes (different alleles)
  account for variations in inherited characters.
• For each character an organism inherits two
  alleles, one from each parent.
• If two alleles differ, then one, the dominant
  allele is fully expressed in the organisms
  appearance.
• The two alleles for each character segregate
  during gamete production.
• Alleles of a gene segregate independently of the
  alleles of other genes.

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Punnett Squares and the Testcross
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• Punnett square- a diagram used to predict the
  result of a genetic cross.
• Testcross- a genetic experiment used to determine
  an organisms genotype.

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Incomplete Dominance

• Incomplete dominance- type of inheritance in
  which the F1 is intermediate in phenotype between
  the parents.
• Neither allele is dominant.
• Self-pollination of the F1 yields a 121 F2
  population.

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Continuous Variation

• Continuous variation- a gradation in phenotype
  indicates that a trait is controlled by two or
  more genes.
• Polygenic inheritance.

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Linkage

• Linkage- the tendency for certain genes to be
  inherited together, owing to the fact that they
  are located on the same chromosome.
• Linked genes- genes that are inherited together.

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Advantage of Sexual Reproduction

• Provides the basic mechanism of evolution
• Genetic variation
• Sexual reproduction gives natural populations the
  ability to adjust to a constantly changing
  environment or to invade a new environment.

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Genetically Engineered Rice
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Genetically Modified Rice
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Genetic Engineering

• Genetic Engineering- the technique of removing,
  modifying, or adding genes to a DNA molecule.
• Improvements in crops
• Longevity
• Resistance to insects
• Resistance to herbicides

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Transgenic Plants

• Tomato with BT gene and without.
• Transgenic tomatoes with and without etr1-1 gene.
• Petunia with and without etr1-1 gene.
• Tobacco with and without a cytokinin gene.

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Transfer of Genes
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Agrobacterium tumefaciens
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Genomics

• Genomics- a field of genetics that attempts to
  understand the content, organization, function,
  and evolution of genetic information in a whole
  organism.

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Arabidopsis thaliana
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Genome

• Genome- all of the genetic information of an
  organism.