8 (3).ppt - Beyond Mendel Each chromosome has hundreds or thousands of genes Genes that code for the same trait are found at the same loci(location Are

8 (3).ppt - Beyond Mendel Each chromosome has hundreds or...

This preview shows page 1 - 16 out of 60 pages.

Beyond Mendel
Image of page 1
Each chromosome has hundreds or thousands of genes. Genes that code for the same trait are found at the same loci (location)
Image of page 2
Image of page 3
Are on the same chromosomes Are inherited together Can be exchanged between homologous chromosomes …… during crossing over
Image of page 4
Results of crosses with linked genes deviate from those expected ratios Note: If Crossing over occurs or if the genes are linked you will not get the typical Mendelian 9:3:3:1 ratio in a dihybrid cross
Image of page 5
Image of page 6
Morgan used Drosophila He crossed two flies that were homozygous for two traits AABB x aabb Wild type body, straight wings Black body, curved wings
Image of page 7
The FI generation : He got the expected AaBb ( heterozygous) showing both dominant traits; (just like Mendels dihybrid cross so far) Mating the F1 he should get: the 9:3:3:1 phenotypic ratio …… typical of a dihybrid cross
Image of page 8
F2 Generation: He did not get the expected 9:3:3: 1 ratio
Image of page 9
Morgan noticed something else in the F2….. he observed : 290 Wildtype body, straight wings 92 black body, curved wings 9 wild-type body, curved wings 9 black body, straight wings 18 flies in the offspring had a very different combination
Image of page 10
Image of page 11
The two genes, body colour and wings DID NOT undergo independent assortment ??? The strange ratio means the genes for body color and wing shape are linked (on the same chromosome) The two dominant traits are on the same chromosome and is inherited together
Image of page 12
2 homologous chromosomes Similar genes Linked Genes
Image of page 13
2 homologous chromosomes Linked Genes
Image of page 14
Chromosomes in each gamete Linked Genes
Image of page 15
Image of page 16

You've reached the end of your free preview.

Want to read all 60 pages?

  • Winter '17
  • John Travis
  • DNA, Genetic linkage, Chromosomal crossover, Thomas Hunt Morgan

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors