Ch 14 – Loose Ends

					A few terms:
 True breeding  pure homozygotes
  (AA or aa)
 Locus  position of a gene on a
  chromosome (pl. loci)
 Progeny testing  if genes are
  unknown, you can test for them by
  mating with known (Testcross)
 Self-pollinate  crossing with self
 Cross off sampling error & transposon
Ch 14 – Loose Ends

 Page 264  The environment can alter
  phenotype.
 Example: Hydrangea
Ch 14 – Loose Ends

   Pedigrees – Check for dominant,
    recessive, or sex-linked traits

                     Which mode is this?
    Ch 14 – Loose Ends
 Which mode is this one?
 What’s the genotype of II-6?
Ch 14 – Loose Ends

   Sickle Cell Disease  heterozygous
    advantage – malaria resistance
Ch 15 – Loose Ends
   Sex – Linkage discovered in fruit flies by
    Thomas Hunt Morgan
Human Sex-linked disorders:

 Albinism
 Colorblindness
 Hemophilia
 Duchene Muscular Dystrophy
 Many others
 Why are males more affected than
  females?
Ch 15 – Loose Ends
   Remember the map unit question from
    the meiosis lab?
                    A & B would tend to be
              A     linked genes because of
              B     their close proximity on the
              C     chromosome.
                    A & C would not.
                    A & B would also have a
                    higher crossover rate than C
                    Why?
Crossing over
Nondisjunction
Trisomy 21: Down’s Syndrome
Altering chromosome structure
    Nondisjunction of X & Y
 Turner's (monosomy X) (sterile females with
  XO)
 Klinefelter's (sterile males with XXY)
  syndromes. Usually have a lower than normal
  IQ and abnormal sexual characteristics.
 Can also have nondisjunction of the Y
  chromosomes which will result in XYY which
  are normal males, but the number of males
  with XYY is 20 times higher in prisons and
  mental institutions than in the normal populace

				
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