Genetic Variation by yurtgc548

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									Genetic Variation




                    www.alsa.org
Goal

 To learn the basic genetic
 mechanisms that determines the traits
 expressed by individuals in a
 population
Natural Selection Theory

 Variation in a population of organisms
   Results of Mutations
   Results of Immigration
   Result of survival features of individual
   organisms
Natural Selection Theory

 Environments are dynamic
   Changing resources
   Climate (long term weather)
   Natural disasters
Natural Selection Theory

 Selective Pressure
   Environmental changes can cause
   pressure
   Organisms unable to adapt quickly
   enough will die
   Organisms that adapt are able to pass
   on their successful traits to future
   generations
Natural Selection Theory

 Isolation
   If one portion of a population is
   separated from another portion then a
   new species may evolve
Natural Selection Theory

 Mechanisms for population change
   Key to change is variation among the
   individuals in the population
   Individuals are unique due to their genes
Genetics
Genetics
Nucleic Acids
  Huge molecules that
  hold information

  DNA
  (deoxyribonucleic
  acid) is the nucleic
  acid that holds all
  the genetic
  information for
  organisms
                         ghr.nlm.nih.gov
DNA
 Genetic code of all living things
 Complete set of blueprints and operating
 instructions for assembling and managing
 one particular kind of organism
 Has four basic building blocks
   Adenine (A)
   Thymine (T)
   Guanine (G)
   Cytosine (C)
DNA
 A and T can only bond with each
 other
 G and C can only bond with each
 other
 When four bases bond together in a
 long chain they form a double helix
 (ladder)
 Typical DNA molecule may be about
 5 cm long
                DNA
DNA found in the nucleus of the cell

DNA is coiled into a compact structure
called a chromosome

Every cell in every plant and animal has a
completed set of chromosomes that define
the organism

Every time the cell divides to produce two
daughter cells the complete set of
chromosomes is produced
Chromosome, Gene, DNA




                   www.phoenix5.org
Genes determine traits
 Genes: are the units of heredity that is a
 sequence of bases (A,T,G,C) that give
 instructions on how to assemble a certain
 protein

 Genes are the sugars, phosphates, and
 bases along the DNA strand in the
 chromosome

 The proteins go to the cells to make things
 such as fats, bone, muscle, nerves, and
 everything else in a living organism
Alleles




          www.monteweston.com
Alleles
  Each gene has two copies which are called
  the alleles.

  (2 alleles= 1 gene)

  Dominant allele the allele that controls
  what will happen or which trait will be
  exhibited (Capital Letter)

  Recessive allele the allele that is
  “overruled” and this trait or function will not
  be seen because of the dominant allele
  (Lower case letter).
Punnett Squares
 A technique for predicting the
 characteristics of offspring

 Example of Punnett Square
Punnett Square


 Always put the dominant allele (G)
 before the recessive allele (g) so
 you would write Gg
 Results:
   One homozygous dominant (GG)
   Two heterozygous (Gg)
   One homozygous recessive (gg)
                     .
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Discovery of Heredityi
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 Gregor Mendel
   Scientist pioneer to work with
   pea plants to show how a
   species can exhibit certain                    history.nih.gov

   characteristics from one
   generation to the next.

   He was the scientist to support
   the idea of dominant (capital
   letter) and recessive (lower case
   letter) traits.
                                       kentsimmons.uwinnipeg.ca
Genotype
 Genotype
    Genotype is the genetic makeup
    of the organism (genes/letters)
    Example:
 (letters represent trait…color in this
    case)
    Pea flower color B=dominant
    allele (purple), b=recessive allele
    (white)
    A purple offspring would have         www.eastbaymom.com
    either a BB or Bb genotype
    A white offspring would only have
    a bb genotype
Phenotype
 Phenotype: how the
 organisms looks
 (trait/picture)

 Example: purple flower,
 white flower, tall plant,
 short plant
Inheritance

 Inheritance is passing genetic
 information from one generation to
 the next

 You inherited alleles from your
 parents

								
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