Human Genetics Ch. 13.1-13.4. Why Study Our DNA? Learn the effects of mutations Understand how...
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- Slide 1
- Human Genetics Ch. 13.1-13.4
- Slide 2
- Why Study Our DNA? Learn the effects of mutations Understand
how genetic diseases are generated Propose possible treatments for
genetic diseases Identify causes of genetic diseases Unfortunately,
inheritance is mostly NON-Mendelian The alleles for traits are
passed on and expressed in complex ways
- Slide 3
- Genetic Linkages What is Mendels Principle of Independent
Assortment? Genes are separated independently into gametes and thus
offspring We have only 23 chromosomes, why is complete independent
assortment impossible? 100,000 of genes and only 23 chromosomes to
be condensed into; some genes have to share the same chromosome
Genes on the same chromosome are linked genes In order to study
inheritance of multiple genes, we are going to have to map out what
genes are on what chromosomes
- Slide 4
- Mapping A Chromosome Morgan and Sturtevant; 1900s
Cross-breeding fruit flies; Drosophila melanogaster (model genetic
studies organism) pr + pr + vg + vg + red eyes; long wings + = wild
type (normal/dominate) prpr vgvg purple eyes; vestigial wings
Expected 1:1:1:1 ratio (all combinations of eye color and wing
type) Got almost 1:1 of parental phenotypes (Red/Long:
Purple/Vestigial Small percent were Red/Vestigial or Purple/Long
(recombinant phenotype)
- Slide 5
- Mapping A Chromosome Why a near 1:1 of the parental phenotypes?
Genes are linked; eye color and wing type are on the same
chromosome Why the small percent of recombinant phenotype? Crossing
Over during meiosis; Genes must have been switched on homologous
chromatids If two sections of a chromosome are switching places,
than what can you conclude about the percent of genes you would see
switched in an organism? The further away the genes are from each
other on the chromosome the more likely they will get switched
- Slide 6
- Recombinant Frequencies Of the F 1 generation; 305 had
recombinant phenotypes of the 2,839 total progeny (offspring). What
is the recombinant frequency? 10.7% (305/2,839 *100) Sturtevant
brilliantly deduced that recombinant frequencies between multiple
linked genes could be use to map out the locations of genes on
their chromosome